diff --git a/README.md b/README.md
index 600ba841e8..cbda7e27c3 100755
--- a/README.md
+++ b/README.md
@@ -28,13 +28,15 @@ More information about these can be found [here](https://github.com/Azure/autore
 ```yaml
 version: 3.0.6246
 use-extension:
-  "@autorest/modelerfour": "4.10.258"
+  "@autorest/modelerfour": "4.10.268"
 
 modelerfour:
   # this runs a pre-namer step to clean up names
   prenamer: true
   # this will flatten modelers marked with 'x-ms-client-flatten'
   flatten-models: true
+  # this will make the content-type parameter always specified
+  always-create-content-type-parameter: true
 
 pipeline:
   typescript: # <- name of plugin
diff --git a/src/generators/modelsGenerator.ts b/src/generators/modelsGenerator.ts
index e2cf7ee6ac..1399b3db8a 100644
--- a/src/generators/modelsGenerator.ts
+++ b/src/generators/modelsGenerator.ts
@@ -402,13 +402,6 @@ function writeOptionalParameters(
           }))
       });
     }
-
-    modelsIndexFile.addTypeAlias({
-      name: `${operationGroupName}${operationName}OptionalParams`,
-      docs: ["Optional parameters."],
-      isExported: true,
-      type: interfaceNames.join(" | ")
-    });
   } else {
     modelsIndexFile.addInterface({
       name: `${operationGroupName}${operationName}OptionalParams`,
diff --git a/src/generators/operationGenerator.ts b/src/generators/operationGenerator.ts
index 6c7ac99703..dcb5bf2a6e 100644
--- a/src/generators/operationGenerator.ts
+++ b/src/generators/operationGenerator.ts
@@ -34,7 +34,8 @@ import {
   SchemaType,
   ParameterLocation,
   ChoiceSchema,
-  SealedChoiceSchema
+  SealedChoiceSchema,
+  ConstantSchema
 } from "@azure-tools/codemodel";
 import { getLanguageMetadata } from "../utils/languageHelpers";
 
@@ -201,7 +202,10 @@ function getOptionsParameter(
   operation: OperationDetails,
   parameters: ParameterDetails[],
   importedModels: Set<string>,
-  { isOptional = true } = {}
+  {
+    isOptional = true,
+    mediaType
+  }: { isOptional?: boolean; mediaType?: string } = {}
 ): ParameterWithDescription {
   let type: string = "coreHttp.OperationOptions";
   if (
@@ -209,7 +213,8 @@ function getOptionsParameter(
       includeOptional: true
     }).some(p => !p.required)
   ) {
-    type = `${operation.typeDetails.typeName}OptionalParams`;
+    const mediaPrefix = mediaType ? `$${mediaType}` : "";
+    type = `${operation.typeDetails.typeName}${mediaPrefix}OptionalParams`;
     importedModels.add(type);
   }
   return {
@@ -286,23 +291,44 @@ type ParameterWithDescription = OptionalKind<
 >;
 
 /**
- * Write operations implementation, extracted from OperationGroupDetails, to the generated file
+ * Gets a list of parameter declarations for each overload the operation supports,
+ * and the list of parameter declarations for the base operation.
  */
-export function writeOperations(
-  operationGroupDetails: OperationGroupDetails,
-  operationGroupClass: ClassDeclaration,
-  importedModels: Set<string>,
+function getOperationParameterSignatures(
+  operation: OperationDetails,
   parameters: ParameterDetails[],
-  isInline = false
+  importedModels: Set<string>,
+  operationGroupClass: ClassDeclaration
 ) {
-  operationGroupDetails.operations.forEach(operation => {
-    const responseName = getResponseType(operation, importedModels);
-    const paramDeclarations = filterOperationParameters(
-      parameters,
-      operation
-    ).map<ParameterWithDescription>(param => {
+  const operationParameters = filterOperationParameters(parameters, operation, {
+    includeContentType: true
+  });
+
+  const operationRequests = operation.requests;
+  const overloadParameterDeclarations: ParameterWithDescription[][] = [];
+  const hasMultipleOverloads = operationRequests.length > 1;
+
+  for (const request of operationRequests) {
+    const requestMediaType = request.mediaType;
+    // filter out parameters that belong to a different media type
+    const requestParameters = operationParameters.filter(
+      ({ targetMediaType }) =>
+        !targetMediaType || requestMediaType === targetMediaType
+    );
+
+    // Convert parameters into TypeScript parameter declarations.
+    const parameterDeclarations = requestParameters.map<
+      ParameterWithDescription
+    >(param => {
       const { usedModels } = param.typeDetails;
-      const type = normalizeTypeName(param.typeDetails);
+      let type = normalizeTypeName(param.typeDetails);
+      if (
+        param.typeDetails.isConstant &&
+        param.typeDetails.typeName === "string" &&
+        param.typeDetails.defaultValue
+      ) {
+        type = `"${param.typeDetails.defaultValue}"`;
+      }
 
       // If the type collides with the class name, use the alias
       const typeName =
@@ -321,39 +347,141 @@ export function writeOperations(
       };
     });
 
-    const allParams = [
-      ...paramDeclarations,
-      getOptionsParameter(operation, parameters, importedModels)
-    ];
+    // add optional parameter
+    const optionalParameter = getOptionsParameter(
+      operation,
+      parameters,
+      importedModels,
+      {
+        mediaType: hasMultipleOverloads ? requestMediaType : undefined
+      }
+    );
+    parameterDeclarations.push(optionalParameter);
+    overloadParameterDeclarations.push(parameterDeclarations);
+  }
+
+  // Create the parameter declarations for the base method signature.
+  const baseMethodParameters = getBaseMethodParameterDeclarations(
+    overloadParameterDeclarations
+  );
+
+  return { overloadParameterDeclarations, baseMethodParameters };
+}
+
+/**
+ * Given a list of operation parameter declarations per overload,
+ * returns a list of the parameter declarations that should appear
+ * in the operation's base signature.
+ *
+ * If `overloadParameterDeclarations` contains the parameter declarations for
+ * just a single overload, then the return value will be the same as the 1st
+ * element in `overloadParameterDeclarations`.
+ * @param overloadParameterDeclarations
+ */
+function getBaseMethodParameterDeclarations(
+  overloadParameterDeclarations: ParameterWithDescription[][]
+): ParameterWithDescription[] {
+  const baseMethodParameters: ParameterWithDescription[] = [];
+  // Need to know which overload has the most parameters to set our upper bound.
+  const maxOverloadSize = Math.max(
+    ...overloadParameterDeclarations.map(params => params.length)
+  );
+  for (let i = 0; i < maxOverloadSize; i++) {
+    // attempt to combine types
+    const declarations: ParameterWithDescription[] = [];
+    for (const overloadParameterDeclaration of overloadParameterDeclarations) {
+      if (overloadParameterDeclaration[i]) {
+        declarations.push(overloadParameterDeclaration[i]);
+      }
+    }
+
+    const declaration = declarations.reduce(
+      (prevDeclaration, curDeclaration) => {
+        prevDeclaration = { ...prevDeclaration };
+        if (curDeclaration.name !== prevDeclaration.name) {
+          // Currently we only generate overloads if an operation supports multiple media types.
+          // Since contentType is always required and the 1st parameter, parameter names/ordering
+          // shouldn't change.
+          // In order to support more variance in parameter naming/ordering, we'll need to be able
+          // to construct the OperationArguments separately for each overload.
+          throw new Error(
+            `Operation overloads with different parameter names/ordering not supported.`
+          );
+        }
+        if (curDeclaration.type !== prevDeclaration.type) {
+          prevDeclaration.type += ` | ${curDeclaration.type}`;
+        }
+        // parameters should be optional if any declaration is optional
+        if (!curDeclaration.hasQuestionToken) {
+          prevDeclaration.hasQuestionToken = curDeclaration.hasQuestionToken;
+        }
+        return prevDeclaration;
+      }
+    );
+    baseMethodParameters.push(declaration);
+  }
+  return baseMethodParameters;
+}
+
+/**
+ * Write operations implementation, extracted from OperationGroupDetails, to the generated file
+ */
+export function writeOperations(
+  operationGroupDetails: OperationGroupDetails,
+  operationGroupClass: ClassDeclaration,
+  importedModels: Set<string>,
+  parameters: ParameterDetails[],
+  isInline = false
+) {
+  operationGroupDetails.operations.forEach(operation => {
+    const {
+      baseMethodParameters,
+      overloadParameterDeclarations
+    } = getOperationParameterSignatures(
+      operation,
+      parameters,
+      importedModels,
+      operationGroupClass
+    );
+    const responseName = getResponseType(operation, importedModels);
 
     const operationMethod = operationGroupClass.addMethod({
       name: normalizeName(operation.name, NameType.Property),
-      parameters: allParams,
+      parameters: baseMethodParameters,
       returnType: `Promise<${responseName}>`,
-      docs: [generateOperationJSDoc(allParams, operation.description)]
+      docs: [
+        generateOperationJSDoc(baseMethodParameters, operation.description)
+      ]
     });
 
-    const sendParams = paramDeclarations.map(p => p.name).join(",");
-
-    if (operation.mediaTypes.size > 1) {
-      // This condition implies that the user can specify a contentType,
-      // and this contentType can change how the request is serialized.
-      writeMultiMediaTypeOperationBody(
-        operationMethod,
-        operation,
-        sendParams,
-        responseName,
-        isInline
+    const sendParams = baseMethodParameters.map(p => p.name).join(",");
+    if (overloadParameterDeclarations.length === 1) {
+      operationMethod.addStatements(
+        `return this${
+          isInline ? "" : ".client"
+        }.sendOperationRequest({${sendParams}${!!sendParams ? "," : ""}}, ${
+          operation.name
+        }OperationSpec) as Promise<${responseName}>`
       );
       return;
     }
 
-    operationMethod.addStatements(
-      `return this${
-        isInline ? "" : ".client"
-      }.sendOperationRequest({${sendParams}${
-        !!sendParams ? "," : ""
-      } options}, ${operation.name}OperationSpec) as Promise<${responseName}>`
+    for (const overload of overloadParameterDeclarations) {
+      operationMethod.addOverload({
+        parameters: overload,
+        returnType: `Promise<${responseName}>`,
+        docs: [generateOperationJSDoc(overload, operation.description)]
+      });
+    }
+
+    // This condition implies that the user can specify a contentType,
+    // and this contentType can change how the request is serialized.
+    writeMultiMediaTypeOperationBody(
+      operationMethod,
+      operation,
+      sendParams,
+      responseName,
+      isInline
     );
   });
 }
@@ -373,43 +501,39 @@ function writeMultiMediaTypeOperationBody(
   let statements = `let operationSpec: coreHttp.OperationSpec;`;
   // We need to use the contentType parameter to determine which spec to use.
   const conditionals: string[] = [];
-  let hasOptionalContentType = false;
   for (const request of operation.requests) {
     const mediaType = request.mediaType!;
-    // check for contentType choice
     const validContentTypes = getContentTypeValues(request);
+
+    // Ensure that a contentType exists, otherwise we won't be able to determine which operation spec to use.
     if (!validContentTypes) {
-      if (hasOptionalContentType) {
-        throw new Error(
-          `Encountered two operation media types that had unspecified values for contentType for operation "${operation.fullName}".`
-        );
-      }
-      hasOptionalContentType = true;
-      // When no value for content-type is present, then we know this is the final 'else' block.
-      conditionals.push(`{
-            operationSpec = ${operation.name}$${mediaType}OperationSpec;
-          }`);
-    } else {
-      conditionals.splice(
-        0,
-        0,
-        `if (
-            options && "contentType" in options &&
-            [${validContentTypes
-              .map(type => `"${type}"`)
-              .join(", ")}].indexOf(options.contentType ?? "") > -1
-          ) {
-            operationSpec = ${operation.name}$${mediaType}OperationSpec;
-          }`
+      throw new Error(
+        `Encountered an operation media type that has unspecified values for the contentType for operation "${operation.fullName}".`
       );
     }
+
+    conditionals.push(
+      `if (
+        [${validContentTypes
+          .map(type => `"${type}"`)
+          .join(", ")}].indexOf(contentType) > -1
+        ) {
+          operationSpec = ${operation.name}$${mediaType}OperationSpec;
+      }`
+    );
   }
+
+  // Add an else clause that throws an error. This should never happen as long as a contentType was provided by the user.
+  conditionals.push(`{
+    throw new TypeError(\`"contentType" must be a valid value but instead was "\${contentType}".\`);
+  }`);
+
   statements += conditionals.join(" else ");
   statements += `return this${
     isInline ? "" : ".client"
   }.sendOperationRequest({${sendParams}${
     !!sendParams ? "," : ""
-  } options}, operationSpec) as Promise<${responseName}>`;
+  }}, operationSpec) as Promise<${responseName}>`;
   operationMethod.addStatements(statements);
 }
 
@@ -419,16 +543,25 @@ function getContentTypeValues(
   const parameters = request.parameters ?? [];
   for (const parameter of parameters) {
     const parameterMetadata = getLanguageMetadata(parameter.language);
+    const paramLowerSerializedName = parameterMetadata.serializedName?.toLowerCase();
+    const parameterInHeader =
+      parameter.protocol.http?.in === ParameterLocation.Header;
     const schema = parameter.schema;
     if (
       (schema.type === SchemaType.Choice ||
         schema.type === SchemaType.SealedChoice) &&
-      parameterMetadata.serializedName.toLowerCase() === "content-type" &&
-      parameter.protocol.http?.in === ParameterLocation.Header
+      paramLowerSerializedName === "content-type" &&
+      parameterInHeader
     ) {
       return (schema as ChoiceSchema | SealedChoiceSchema).choices.map(
         c => c.value as string
       );
+    } else if (
+      schema.type === SchemaType.Constant &&
+      paramLowerSerializedName === "content-type" &&
+      parameterInHeader
+    ) {
+      return [(schema as ConstantSchema).value.value];
     }
   }
   return;
diff --git a/src/generators/utils/parameterUtils.ts b/src/generators/utils/parameterUtils.ts
index fe40f91bbb..dc728c0e93 100644
--- a/src/generators/utils/parameterUtils.ts
+++ b/src/generators/utils/parameterUtils.ts
@@ -3,7 +3,11 @@
 
 import { ParameterDetails } from "../../models/parameterDetails";
 import { OperationDetails } from "../../models/operationDetails";
-import { ImplementationLocation, SchemaType } from "@azure-tools/codemodel";
+import {
+  ImplementationLocation,
+  SchemaType,
+  ParameterLocation
+} from "@azure-tools/codemodel";
 import { wrapString, IndentationType } from "./stringUtils";
 
 interface ParameterFilterOptions {
@@ -12,6 +16,8 @@ interface ParameterFilterOptions {
   includeUriParameters?: boolean;
   includeGlobalParameters?: boolean;
   includeConstantParameters?: boolean;
+  // Whether the contentType parameter should always be included.
+  includeContentType?: boolean;
 }
 
 /**
@@ -28,13 +34,18 @@ export function filterOperationParameters(
     includeOptional,
     includeClientParams,
     includeGlobalParameters,
-    includeConstantParameters
+    includeConstantParameters,
+    includeContentType
   }: ParameterFilterOptions = {}
 ) {
+  const isContentType = (param: ParameterDetails) =>
+    param.name === "contentType" && param.location === ParameterLocation.Header;
+
   const optionalFilter = (param: ParameterDetails) =>
     !!(includeOptional || param.required);
 
   const constantFilter = (param: ParameterDetails) =>
+    (includeContentType && isContentType(param)) ||
     !!(includeConstantParameters || param.schemaType !== SchemaType.Constant);
 
   const clientParamFilter = (param: ParameterDetails) =>
diff --git a/src/transforms/extensions.ts b/src/transforms/extensions.ts
index d6e7b3fea9..b457f6fd35 100644
--- a/src/transforms/extensions.ts
+++ b/src/transforms/extensions.ts
@@ -25,10 +25,8 @@ export function normalizeModelWithExtensions(codeModel: CodeModel) {
 }
 
 /**
- * This updates parameters that should be serialized as a Content-Type header.
- * This logic should be able to be removed once modelerfour includes
- * the serializedName and http protocol details:
- * https://github.com/Azure/autorest.modelerfour/issues/207
+ * This updates the contentType parameter for operations
+ * that support multiple media types to be required.
  * @param codeModel
  */
 function normalizeMultipleContentTypes(codeModel: CodeModel) {
@@ -38,7 +36,7 @@ function normalizeMultipleContentTypes(codeModel: CodeModel) {
 
     for (const operation of operations) {
       const requests = operation.requests;
-      if (!requests) {
+      if (!requests || requests.length <= 1) {
         continue;
       }
 
@@ -50,15 +48,8 @@ function normalizeMultipleContentTypes(codeModel: CodeModel) {
 
         for (const parameter of parameters) {
           const parameterMetadata = getLanguageMetadata(parameter.language);
-          if (
-            !parameter.protocol.http &&
-            !parameterMetadata.serializedName &&
-            parameterMetadata.name.toLowerCase() === "contenttype"
-          ) {
-            parameterMetadata.serializedName = "Content-Type";
-            const http = new Protocol();
-            http.in = ParameterLocation.Header;
-            parameter.protocol.http = http;
+          if (parameterMetadata.name.toLowerCase() === "contenttype") {
+            parameter.required = true;
           }
         }
       }
diff --git a/src/utils/schemaHelpers.ts b/src/utils/schemaHelpers.ts
index 279391c03d..f7c866f84c 100644
--- a/src/utils/schemaHelpers.ts
+++ b/src/utils/schemaHelpers.ts
@@ -59,7 +59,6 @@ export function getTypeForSchema(schema: Schema): TypeDetails {
     case SchemaType.Constant:
       const constantSchema = schema as ConstantSchema;
       const constantType = getTypeForSchema(constantSchema.valueType);
-      typeName = constantType.typeName;
       kind = constantType.kind;
       if (isModelNeeded(constantType)) {
         usedModels.push(typeName);
@@ -69,6 +68,7 @@ export function getTypeForSchema(schema: Schema): TypeDetails {
         constantSchema.valueType.type,
         false
       );
+      typeName = constantType.typeName;
       break;
     case SchemaType.DateTime:
     case SchemaType.Date:
diff --git a/test/integration/generated/azureReport/src/reportClient.ts b/test/integration/generated/azureReport/src/reportClient.ts
index a60e98319b..91dd024ae5 100644
--- a/test/integration/generated/azureReport/src/reportClient.ts
+++ b/test/integration/generated/azureReport/src/reportClient.ts
@@ -12,8 +12,8 @@ import * as Models from "./models";
 import * as Mappers from "./models/mappers";
 import { ReportClientContext } from "./reportClientContext";
 import {
-  ReportClientGetReportResponse,
-  ReportClientGetReportOptionalParams
+  ReportClientGetReportOptionalParams,
+  ReportClientGetReportResponse
 } from "./models";
 
 class ReportClient extends ReportClientContext {
diff --git a/test/integration/generated/bodyArray/src/models/parameters.ts b/test/integration/generated/bodyArray/src/models/parameters.ts
index 2f8829e742..ab1f0cf102 100644
--- a/test/integration/generated/bodyArray/src/models/parameters.ts
+++ b/test/integration/generated/bodyArray/src/models/parameters.ts
@@ -21,6 +21,18 @@ export const $host: coreHttp.OperationURLParameter = {
   skipEncoding: true
 };
 
+export const contentType: coreHttp.OperationParameter = {
+  parameterPath: ["options", "contentType"],
+  mapper: {
+    defaultValue: "application/json",
+    serializedName: "Content-Type",
+    isConstant: true,
+    type: {
+      name: "String"
+    }
+  }
+};
+
 export const arrayBody: coreHttp.OperationParameter = {
   parameterPath: "arrayBody",
   mapper: {
diff --git a/test/integration/generated/bodyArray/src/operations/array.ts b/test/integration/generated/bodyArray/src/operations/array.ts
index a6f8521e8d..e2b15e30bf 100644
--- a/test/integration/generated/bodyArray/src/operations/array.ts
+++ b/test/integration/generated/bodyArray/src/operations/array.ts
@@ -1106,6 +1106,7 @@ const putEmptyOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getBooleanTfftOperationSpec: coreHttp.OperationSpec = {
@@ -1139,6 +1140,7 @@ const putBooleanTfftOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody1,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getBooleanInvalidNullOperationSpec: coreHttp.OperationSpec = {
@@ -1212,6 +1214,7 @@ const putIntegerValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody2,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getIntInvalidNullOperationSpec: coreHttp.OperationSpec = {
@@ -1285,6 +1288,7 @@ const putLongValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody3,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getLongInvalidNullOperationSpec: coreHttp.OperationSpec = {
@@ -1358,6 +1362,7 @@ const putFloatValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody4,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getFloatInvalidNullOperationSpec: coreHttp.OperationSpec = {
@@ -1431,6 +1436,7 @@ const putDoubleValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody5,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getDoubleInvalidNullOperationSpec: coreHttp.OperationSpec = {
@@ -1504,6 +1510,7 @@ const putStringValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody6,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getEnumValidOperationSpec: coreHttp.OperationSpec = {
@@ -1540,6 +1547,7 @@ const putEnumValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody7,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getStringEnumValidOperationSpec: coreHttp.OperationSpec = {
@@ -1573,6 +1581,7 @@ const putStringEnumValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody8,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getStringWithNullOperationSpec: coreHttp.OperationSpec = {
@@ -1646,6 +1655,7 @@ const putUuidValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody9,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getUuidInvalidCharsOperationSpec: coreHttp.OperationSpec = {
@@ -1699,6 +1709,7 @@ const putDateValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody10,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getDateInvalidNullOperationSpec: coreHttp.OperationSpec = {
@@ -1772,6 +1783,7 @@ const putDateTimeValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody11,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getDateTimeInvalidNullOperationSpec: coreHttp.OperationSpec = {
@@ -1848,6 +1860,7 @@ const putDateTimeRfc1123ValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody12,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getDurationValidOperationSpec: coreHttp.OperationSpec = {
@@ -1881,6 +1894,7 @@ const putDurationValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody13,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getByteValidOperationSpec: coreHttp.OperationSpec = {
@@ -1914,6 +1928,7 @@ const putByteValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody14,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getByteInvalidNullOperationSpec: coreHttp.OperationSpec = {
@@ -2067,6 +2082,7 @@ const putComplexValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody15,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getArrayNullOperationSpec: coreHttp.OperationSpec = {
@@ -2210,6 +2226,7 @@ const putArrayValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody16,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getDictionaryNullOperationSpec: coreHttp.OperationSpec = {
@@ -2353,5 +2370,6 @@ const putDictionaryValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody17,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
diff --git a/test/integration/generated/bodyBoolean/src/models/parameters.ts b/test/integration/generated/bodyBoolean/src/models/parameters.ts
index 3e7e192825..3b313fa430 100644
--- a/test/integration/generated/bodyBoolean/src/models/parameters.ts
+++ b/test/integration/generated/bodyBoolean/src/models/parameters.ts
@@ -21,6 +21,18 @@ export const $host: coreHttp.OperationURLParameter = {
   skipEncoding: true
 };
 
+export const contentType: coreHttp.OperationParameter = {
+  parameterPath: ["options", "contentType"],
+  mapper: {
+    defaultValue: "application/json",
+    serializedName: "Content-Type",
+    isConstant: true,
+    type: {
+      name: "String"
+    }
+  }
+};
+
 export const boolBody: coreHttp.OperationParameter = {
   parameterPath: "boolBody",
   mapper: {
diff --git a/test/integration/generated/bodyBoolean/src/operations/bool.ts b/test/integration/generated/bodyBoolean/src/operations/bool.ts
index 2d1009432a..3e20815ac1 100644
--- a/test/integration/generated/bodyBoolean/src/operations/bool.ts
+++ b/test/integration/generated/bodyBoolean/src/operations/bool.ts
@@ -130,6 +130,7 @@ const putTrueOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.boolBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getFalseOperationSpec: coreHttp.OperationSpec = {
@@ -157,6 +158,7 @@ const putFalseOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.boolBody1,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getNullOperationSpec: coreHttp.OperationSpec = {
diff --git a/test/integration/generated/bodyBooleanQuirks/src/models/parameters.ts b/test/integration/generated/bodyBooleanQuirks/src/models/parameters.ts
index ef5d8012f3..89d27c0dc4 100644
--- a/test/integration/generated/bodyBooleanQuirks/src/models/parameters.ts
+++ b/test/integration/generated/bodyBooleanQuirks/src/models/parameters.ts
@@ -21,6 +21,18 @@ export const $host: coreHttp.OperationURLParameter = {
   skipEncoding: true
 };
 
+export const contentType: coreHttp.OperationParameter = {
+  parameterPath: ["options", "contentType"],
+  mapper: {
+    defaultValue: "application/json",
+    serializedName: "Content-Type",
+    isConstant: true,
+    type: {
+      name: "String"
+    }
+  }
+};
+
 export const boolBody: coreHttp.OperationParameter = {
   parameterPath: "boolBody",
   mapper: {
diff --git a/test/integration/generated/bodyBooleanQuirks/src/operations/bool.ts b/test/integration/generated/bodyBooleanQuirks/src/operations/bool.ts
index 147cd5d679..e1dd0f68aa 100644
--- a/test/integration/generated/bodyBooleanQuirks/src/operations/bool.ts
+++ b/test/integration/generated/bodyBooleanQuirks/src/operations/bool.ts
@@ -136,6 +136,7 @@ const putTrueOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.boolBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getFalseOperationSpec: coreHttp.OperationSpec = {
@@ -163,6 +164,7 @@ const putFalseOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.boolBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getNullOperationSpec: coreHttp.OperationSpec = {
diff --git a/test/integration/generated/bodyByte/src/models/parameters.ts b/test/integration/generated/bodyByte/src/models/parameters.ts
index 31965601aa..4974a51c7e 100644
--- a/test/integration/generated/bodyByte/src/models/parameters.ts
+++ b/test/integration/generated/bodyByte/src/models/parameters.ts
@@ -21,6 +21,18 @@ export const $host: coreHttp.OperationURLParameter = {
   skipEncoding: true
 };
 
+export const contentType: coreHttp.OperationParameter = {
+  parameterPath: ["options", "contentType"],
+  mapper: {
+    defaultValue: "application/json",
+    serializedName: "Content-Type",
+    isConstant: true,
+    type: {
+      name: "String"
+    }
+  }
+};
+
 export const byteBody: coreHttp.OperationParameter = {
   parameterPath: "byteBody",
   mapper: {
diff --git a/test/integration/generated/bodyByte/src/operations/byte.ts b/test/integration/generated/bodyByte/src/operations/byte.ts
index e1318e26dc..6a3ddb6e38 100644
--- a/test/integration/generated/bodyByte/src/operations/byte.ts
+++ b/test/integration/generated/bodyByte/src/operations/byte.ts
@@ -151,6 +151,7 @@ const putNonAsciiOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.byteBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getInvalidOperationSpec: coreHttp.OperationSpec = {
diff --git a/test/integration/generated/bodyComplex/src/models/parameters.ts b/test/integration/generated/bodyComplex/src/models/parameters.ts
index 9e4204de5b..2013c7f41c 100644
--- a/test/integration/generated/bodyComplex/src/models/parameters.ts
+++ b/test/integration/generated/bodyComplex/src/models/parameters.ts
@@ -21,6 +21,18 @@ export const $host: coreHttp.OperationURLParameter = {
   skipEncoding: true
 };
 
+export const contentType: coreHttp.OperationParameter = {
+  parameterPath: ["options", "contentType"],
+  mapper: {
+    defaultValue: "application/json",
+    serializedName: "Content-Type",
+    isConstant: true,
+    type: {
+      name: "String"
+    }
+  }
+};
+
 export const complexBody: coreHttp.OperationParameter = {
   parameterPath: "complexBody",
   mapper: Mappers.Basic
diff --git a/test/integration/generated/bodyComplex/src/operations/array.ts b/test/integration/generated/bodyComplex/src/operations/array.ts
index cddf2fdfd1..3960b1b65b 100644
--- a/test/integration/generated/bodyComplex/src/operations/array.ts
+++ b/test/integration/generated/bodyComplex/src/operations/array.ts
@@ -130,6 +130,7 @@ const putValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody12,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getEmptyOperationSpec: coreHttp.OperationSpec = {
@@ -157,6 +158,7 @@ const putEmptyOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody13,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getNotProvidedOperationSpec: coreHttp.OperationSpec = {
diff --git a/test/integration/generated/bodyComplex/src/operations/basic.ts b/test/integration/generated/bodyComplex/src/operations/basic.ts
index 6cc886ab45..f809b9bf41 100644
--- a/test/integration/generated/bodyComplex/src/operations/basic.ts
+++ b/test/integration/generated/bodyComplex/src/operations/basic.ts
@@ -141,6 +141,7 @@ const putValidOperationSpec: coreHttp.OperationSpec = {
   requestBody: Parameters.complexBody,
   queryParameters: [Parameters.apiVersion],
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getInvalidOperationSpec: coreHttp.OperationSpec = {
diff --git a/test/integration/generated/bodyComplex/src/operations/dictionary.ts b/test/integration/generated/bodyComplex/src/operations/dictionary.ts
index 32106e9509..8b12be5b75 100644
--- a/test/integration/generated/bodyComplex/src/operations/dictionary.ts
+++ b/test/integration/generated/bodyComplex/src/operations/dictionary.ts
@@ -144,6 +144,7 @@ const putValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody14,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getEmptyOperationSpec: coreHttp.OperationSpec = {
@@ -171,6 +172,7 @@ const putEmptyOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody15,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getNullOperationSpec: coreHttp.OperationSpec = {
diff --git a/test/integration/generated/bodyComplex/src/operations/inheritance.ts b/test/integration/generated/bodyComplex/src/operations/inheritance.ts
index 9590e752ce..75efe76dfa 100644
--- a/test/integration/generated/bodyComplex/src/operations/inheritance.ts
+++ b/test/integration/generated/bodyComplex/src/operations/inheritance.ts
@@ -85,5 +85,6 @@ const putValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody16,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
diff --git a/test/integration/generated/bodyComplex/src/operations/polymorphicrecursive.ts b/test/integration/generated/bodyComplex/src/operations/polymorphicrecursive.ts
index 14df8f4081..6f21f1b221 100644
--- a/test/integration/generated/bodyComplex/src/operations/polymorphicrecursive.ts
+++ b/test/integration/generated/bodyComplex/src/operations/polymorphicrecursive.ts
@@ -135,5 +135,6 @@ const putValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody20,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
diff --git a/test/integration/generated/bodyComplex/src/operations/polymorphism.ts b/test/integration/generated/bodyComplex/src/operations/polymorphism.ts
index 0648ac7c84..83ed4eeb9d 100644
--- a/test/integration/generated/bodyComplex/src/operations/polymorphism.ts
+++ b/test/integration/generated/bodyComplex/src/operations/polymorphism.ts
@@ -254,6 +254,7 @@ const putValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody17,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getDotSyntaxOperationSpec: coreHttp.OperationSpec = {
@@ -323,6 +324,7 @@ const putComplicatedOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody18,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const putMissingDiscriminatorOperationSpec: coreHttp.OperationSpec = {
@@ -338,6 +340,7 @@ const putMissingDiscriminatorOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody18,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const putValidMissingRequiredOperationSpec: coreHttp.OperationSpec = {
@@ -351,5 +354,6 @@ const putValidMissingRequiredOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody19,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
diff --git a/test/integration/generated/bodyComplex/src/operations/primitive.ts b/test/integration/generated/bodyComplex/src/operations/primitive.ts
index c3eb37586a..7c241d7746 100644
--- a/test/integration/generated/bodyComplex/src/operations/primitive.ts
+++ b/test/integration/generated/bodyComplex/src/operations/primitive.ts
@@ -387,6 +387,7 @@ const putIntOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody1,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getLongOperationSpec: coreHttp.OperationSpec = {
@@ -414,6 +415,7 @@ const putLongOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody2,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getFloatOperationSpec: coreHttp.OperationSpec = {
@@ -441,6 +443,7 @@ const putFloatOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody3,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getDoubleOperationSpec: coreHttp.OperationSpec = {
@@ -468,6 +471,7 @@ const putDoubleOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody4,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getBoolOperationSpec: coreHttp.OperationSpec = {
@@ -495,6 +499,7 @@ const putBoolOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody5,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getStringOperationSpec: coreHttp.OperationSpec = {
@@ -522,6 +527,7 @@ const putStringOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody6,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getDateOperationSpec: coreHttp.OperationSpec = {
@@ -549,6 +555,7 @@ const putDateOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody7,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getDateTimeOperationSpec: coreHttp.OperationSpec = {
@@ -576,6 +583,7 @@ const putDateTimeOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody8,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getDateTimeRfc1123OperationSpec: coreHttp.OperationSpec = {
@@ -603,6 +611,7 @@ const putDateTimeRfc1123OperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody9,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getDurationOperationSpec: coreHttp.OperationSpec = {
@@ -630,6 +639,7 @@ const putDurationOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody10,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getByteOperationSpec: coreHttp.OperationSpec = {
@@ -657,5 +667,6 @@ const putByteOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody11,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
diff --git a/test/integration/generated/bodyComplex/src/operations/readonlyproperty.ts b/test/integration/generated/bodyComplex/src/operations/readonlyproperty.ts
index 9ea054e83e..46eab57a95 100644
--- a/test/integration/generated/bodyComplex/src/operations/readonlyproperty.ts
+++ b/test/integration/generated/bodyComplex/src/operations/readonlyproperty.ts
@@ -83,5 +83,6 @@ const putValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.complexBody21,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
diff --git a/test/integration/generated/bodyDate/src/models/parameters.ts b/test/integration/generated/bodyDate/src/models/parameters.ts
index 4a46525500..c5de1e55ae 100644
--- a/test/integration/generated/bodyDate/src/models/parameters.ts
+++ b/test/integration/generated/bodyDate/src/models/parameters.ts
@@ -21,6 +21,18 @@ export const $host: coreHttp.OperationURLParameter = {
   skipEncoding: true
 };
 
+export const contentType: coreHttp.OperationParameter = {
+  parameterPath: ["options", "contentType"],
+  mapper: {
+    defaultValue: "application/json",
+    serializedName: "Content-Type",
+    isConstant: true,
+    type: {
+      name: "String"
+    }
+  }
+};
+
 export const dateBody: coreHttp.OperationParameter = {
   parameterPath: "dateBody",
   mapper: {
diff --git a/test/integration/generated/bodyDate/src/operations/date.ts b/test/integration/generated/bodyDate/src/operations/date.ts
index 69fcfec8f4..1a997a4eef 100644
--- a/test/integration/generated/bodyDate/src/operations/date.ts
+++ b/test/integration/generated/bodyDate/src/operations/date.ts
@@ -212,6 +212,7 @@ const putMaxDateOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.dateBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getMaxDateOperationSpec: coreHttp.OperationSpec = {
@@ -239,6 +240,7 @@ const putMinDateOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.dateBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getMinDateOperationSpec: coreHttp.OperationSpec = {
diff --git a/test/integration/generated/bodyDateTime/src/models/parameters.ts b/test/integration/generated/bodyDateTime/src/models/parameters.ts
index 8be62c3fc8..8e73e59172 100644
--- a/test/integration/generated/bodyDateTime/src/models/parameters.ts
+++ b/test/integration/generated/bodyDateTime/src/models/parameters.ts
@@ -21,6 +21,18 @@ export const $host: coreHttp.OperationURLParameter = {
   skipEncoding: true
 };
 
+export const contentType: coreHttp.OperationParameter = {
+  parameterPath: ["options", "contentType"],
+  mapper: {
+    defaultValue: "application/json",
+    serializedName: "Content-Type",
+    isConstant: true,
+    type: {
+      name: "String"
+    }
+  }
+};
+
 export const datetimeBody: coreHttp.OperationParameter = {
   parameterPath: "datetimeBody",
   mapper: {
diff --git a/test/integration/generated/bodyDateTime/src/operations/datetime.ts b/test/integration/generated/bodyDateTime/src/operations/datetime.ts
index 236a31d9dd..2501e430bb 100644
--- a/test/integration/generated/bodyDateTime/src/operations/datetime.ts
+++ b/test/integration/generated/bodyDateTime/src/operations/datetime.ts
@@ -399,6 +399,7 @@ const putUtcMaxDateTimeOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.datetimeBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const putUtcMaxDateTime7DigitsOperationSpec: coreHttp.OperationSpec = {
@@ -412,6 +413,7 @@ const putUtcMaxDateTime7DigitsOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.datetimeBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getUtcLowercaseMaxDateTimeOperationSpec: coreHttp.OperationSpec = {
@@ -467,6 +469,7 @@ const putLocalPositiveOffsetMaxDateTimeOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.datetimeBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getLocalPositiveOffsetLowercaseMaxDateTimeOperationSpec: coreHttp.OperationSpec = {
@@ -508,6 +511,7 @@ const putLocalNegativeOffsetMaxDateTimeOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.datetimeBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getLocalNegativeOffsetUppercaseMaxDateTimeOperationSpec: coreHttp.OperationSpec = {
@@ -549,6 +553,7 @@ const putUtcMinDateTimeOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.datetimeBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getUtcMinDateTimeOperationSpec: coreHttp.OperationSpec = {
@@ -576,6 +581,7 @@ const putLocalPositiveOffsetMinDateTimeOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.datetimeBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getLocalPositiveOffsetMinDateTimeOperationSpec: coreHttp.OperationSpec = {
@@ -603,6 +609,7 @@ const putLocalNegativeOffsetMinDateTimeOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.datetimeBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getLocalNegativeOffsetMinDateTimeOperationSpec: coreHttp.OperationSpec = {
diff --git a/test/integration/generated/bodyDateTimeRfc1123/src/models/parameters.ts b/test/integration/generated/bodyDateTimeRfc1123/src/models/parameters.ts
index f79e884199..becf933193 100644
--- a/test/integration/generated/bodyDateTimeRfc1123/src/models/parameters.ts
+++ b/test/integration/generated/bodyDateTimeRfc1123/src/models/parameters.ts
@@ -21,6 +21,18 @@ export const $host: coreHttp.OperationURLParameter = {
   skipEncoding: true
 };
 
+export const contentType: coreHttp.OperationParameter = {
+  parameterPath: ["options", "contentType"],
+  mapper: {
+    defaultValue: "application/json",
+    serializedName: "Content-Type",
+    isConstant: true,
+    type: {
+      name: "String"
+    }
+  }
+};
+
 export const datetimeBody: coreHttp.OperationParameter = {
   parameterPath: "datetimeBody",
   mapper: {
diff --git a/test/integration/generated/bodyDateTimeRfc1123/src/operations/datetimerfc1123.ts b/test/integration/generated/bodyDateTimeRfc1123/src/operations/datetimerfc1123.ts
index 25d1309cfe..0a67f033aa 100644
--- a/test/integration/generated/bodyDateTimeRfc1123/src/operations/datetimerfc1123.ts
+++ b/test/integration/generated/bodyDateTimeRfc1123/src/operations/datetimerfc1123.ts
@@ -238,6 +238,7 @@ const putUtcMaxDateTimeOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.datetimeBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getUtcLowercaseMaxDateTimeOperationSpec: coreHttp.OperationSpec = {
@@ -285,6 +286,7 @@ const putUtcMinDateTimeOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.datetimeBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getUtcMinDateTimeOperationSpec: coreHttp.OperationSpec = {
diff --git a/test/integration/generated/bodyDictionary/src/models/parameters.ts b/test/integration/generated/bodyDictionary/src/models/parameters.ts
index a69ece5850..a9c6504563 100644
--- a/test/integration/generated/bodyDictionary/src/models/parameters.ts
+++ b/test/integration/generated/bodyDictionary/src/models/parameters.ts
@@ -21,6 +21,18 @@ export const $host: coreHttp.OperationURLParameter = {
   skipEncoding: true
 };
 
+export const contentType: coreHttp.OperationParameter = {
+  parameterPath: ["options", "contentType"],
+  mapper: {
+    defaultValue: "application/json",
+    serializedName: "Content-Type",
+    isConstant: true,
+    type: {
+      name: "String"
+    }
+  }
+};
+
 export const arrayBody: coreHttp.OperationParameter = {
   parameterPath: "arrayBody",
   mapper: {
diff --git a/test/integration/generated/bodyDictionary/src/operations/dictionary.ts b/test/integration/generated/bodyDictionary/src/operations/dictionary.ts
index 3f7bbec76f..dace8ac9d1 100644
--- a/test/integration/generated/bodyDictionary/src/operations/dictionary.ts
+++ b/test/integration/generated/bodyDictionary/src/operations/dictionary.ts
@@ -1025,6 +1025,7 @@ const putEmptyOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getNullValueOperationSpec: coreHttp.OperationSpec = {
@@ -1138,6 +1139,7 @@ const putBooleanTfftOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody1,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getBooleanInvalidNullOperationSpec: coreHttp.OperationSpec = {
@@ -1211,6 +1213,7 @@ const putIntegerValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody2,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getIntInvalidNullOperationSpec: coreHttp.OperationSpec = {
@@ -1284,6 +1287,7 @@ const putLongValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody3,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getLongInvalidNullOperationSpec: coreHttp.OperationSpec = {
@@ -1357,6 +1361,7 @@ const putFloatValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody4,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getFloatInvalidNullOperationSpec: coreHttp.OperationSpec = {
@@ -1430,6 +1435,7 @@ const putDoubleValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody5,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getDoubleInvalidNullOperationSpec: coreHttp.OperationSpec = {
@@ -1503,6 +1509,7 @@ const putStringValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody6,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getStringWithNullOperationSpec: coreHttp.OperationSpec = {
@@ -1576,6 +1583,7 @@ const putDateValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody7,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getDateInvalidNullOperationSpec: coreHttp.OperationSpec = {
@@ -1649,6 +1657,7 @@ const putDateTimeValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody8,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getDateTimeInvalidNullOperationSpec: coreHttp.OperationSpec = {
@@ -1725,6 +1734,7 @@ const putDateTimeRfc1123ValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody9,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getDurationValidOperationSpec: coreHttp.OperationSpec = {
@@ -1758,6 +1768,7 @@ const putDurationValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody10,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getByteValidOperationSpec: coreHttp.OperationSpec = {
@@ -1791,6 +1802,7 @@ const putByteValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody11,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getByteInvalidNullOperationSpec: coreHttp.OperationSpec = {
@@ -1944,6 +1956,7 @@ const putComplexValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody12,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getArrayNullOperationSpec: coreHttp.OperationSpec = {
@@ -2096,6 +2109,7 @@ const putArrayValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody13,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getDictionaryNullOperationSpec: coreHttp.OperationSpec = {
@@ -2209,5 +2223,6 @@ const putDictionaryValidOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.arrayBody14,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
diff --git a/test/integration/generated/bodyDuration/src/models/parameters.ts b/test/integration/generated/bodyDuration/src/models/parameters.ts
index 5dbfc2b310..066cd0d602 100644
--- a/test/integration/generated/bodyDuration/src/models/parameters.ts
+++ b/test/integration/generated/bodyDuration/src/models/parameters.ts
@@ -21,6 +21,18 @@ export const $host: coreHttp.OperationURLParameter = {
   skipEncoding: true
 };
 
+export const contentType: coreHttp.OperationParameter = {
+  parameterPath: ["options", "contentType"],
+  mapper: {
+    defaultValue: "application/json",
+    serializedName: "Content-Type",
+    isConstant: true,
+    type: {
+      name: "String"
+    }
+  }
+};
+
 export const durationBody: coreHttp.OperationParameter = {
   parameterPath: "durationBody",
   mapper: {
diff --git a/test/integration/generated/bodyDuration/src/operations/duration.ts b/test/integration/generated/bodyDuration/src/operations/duration.ts
index 4d3a64a3a4..af1bf2dd08 100644
--- a/test/integration/generated/bodyDuration/src/operations/duration.ts
+++ b/test/integration/generated/bodyDuration/src/operations/duration.ts
@@ -113,6 +113,7 @@ const putPositiveDurationOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.durationBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getPositiveDurationOperationSpec: coreHttp.OperationSpec = {
diff --git a/test/integration/generated/bodyInteger/src/models/parameters.ts b/test/integration/generated/bodyInteger/src/models/parameters.ts
index 1b42ea6d99..10d5202de1 100644
--- a/test/integration/generated/bodyInteger/src/models/parameters.ts
+++ b/test/integration/generated/bodyInteger/src/models/parameters.ts
@@ -21,6 +21,18 @@ export const $host: coreHttp.OperationURLParameter = {
   skipEncoding: true
 };
 
+export const contentType: coreHttp.OperationParameter = {
+  parameterPath: ["options", "contentType"],
+  mapper: {
+    defaultValue: "application/json",
+    serializedName: "Content-Type",
+    isConstant: true,
+    type: {
+      name: "String"
+    }
+  }
+};
+
 export const intBody: coreHttp.OperationParameter = {
   parameterPath: "intBody",
   mapper: {
diff --git a/test/integration/generated/bodyInteger/src/operations/int.ts b/test/integration/generated/bodyInteger/src/operations/int.ts
index 34c7d6bbca..36c55ab87e 100644
--- a/test/integration/generated/bodyInteger/src/operations/int.ts
+++ b/test/integration/generated/bodyInteger/src/operations/int.ts
@@ -325,6 +325,7 @@ const putMax32OperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.intBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const putMax64OperationSpec: coreHttp.OperationSpec = {
@@ -338,6 +339,7 @@ const putMax64OperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.intBody1,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const putMin32OperationSpec: coreHttp.OperationSpec = {
@@ -351,6 +353,7 @@ const putMin32OperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.intBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const putMin64OperationSpec: coreHttp.OperationSpec = {
@@ -364,6 +367,7 @@ const putMin64OperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.intBody1,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getUnixTimeOperationSpec: coreHttp.OperationSpec = {
@@ -391,6 +395,7 @@ const putUnixTimeDateOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.intBody2,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getInvalidUnixTimeOperationSpec: coreHttp.OperationSpec = {
diff --git a/test/integration/generated/bodyNumber/src/models/parameters.ts b/test/integration/generated/bodyNumber/src/models/parameters.ts
index 5f42e7310c..3899142a2a 100644
--- a/test/integration/generated/bodyNumber/src/models/parameters.ts
+++ b/test/integration/generated/bodyNumber/src/models/parameters.ts
@@ -21,6 +21,18 @@ export const $host: coreHttp.OperationURLParameter = {
   skipEncoding: true
 };
 
+export const contentType: coreHttp.OperationParameter = {
+  parameterPath: ["options", "contentType"],
+  mapper: {
+    defaultValue: "application/json",
+    serializedName: "Content-Type",
+    isConstant: true,
+    type: {
+      name: "String"
+    }
+  }
+};
+
 export const numberBody: coreHttp.OperationParameter = {
   parameterPath: "numberBody",
   mapper: {
diff --git a/test/integration/generated/bodyNumber/src/operations/number.ts b/test/integration/generated/bodyNumber/src/operations/number.ts
index 2182865760..f9477181ee 100644
--- a/test/integration/generated/bodyNumber/src/operations/number.ts
+++ b/test/integration/generated/bodyNumber/src/operations/number.ts
@@ -434,6 +434,7 @@ const putBigFloatOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.numberBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getBigFloatOperationSpec: coreHttp.OperationSpec = {
@@ -461,6 +462,7 @@ const putBigDoubleOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.numberBody1,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getBigDoubleOperationSpec: coreHttp.OperationSpec = {
@@ -488,6 +490,7 @@ const putBigDoublePositiveDecimalOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.numberBody2,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getBigDoublePositiveDecimalOperationSpec: coreHttp.OperationSpec = {
@@ -515,6 +518,7 @@ const putBigDoubleNegativeDecimalOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.numberBody3,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getBigDoubleNegativeDecimalOperationSpec: coreHttp.OperationSpec = {
@@ -542,6 +546,7 @@ const putBigDecimalOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.numberBody4,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getBigDecimalOperationSpec: coreHttp.OperationSpec = {
@@ -569,6 +574,7 @@ const putBigDecimalPositiveDecimalOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.numberBody5,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getBigDecimalPositiveDecimalOperationSpec: coreHttp.OperationSpec = {
@@ -596,6 +602,7 @@ const putBigDecimalNegativeDecimalOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.numberBody6,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getBigDecimalNegativeDecimalOperationSpec: coreHttp.OperationSpec = {
@@ -623,6 +630,7 @@ const putSmallFloatOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.numberBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getSmallFloatOperationSpec: coreHttp.OperationSpec = {
@@ -650,6 +658,7 @@ const putSmallDoubleOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.numberBody1,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getSmallDoubleOperationSpec: coreHttp.OperationSpec = {
@@ -677,6 +686,7 @@ const putSmallDecimalOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.numberBody4,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getSmallDecimalOperationSpec: coreHttp.OperationSpec = {
diff --git a/test/integration/generated/bodyString/src/models/parameters.ts b/test/integration/generated/bodyString/src/models/parameters.ts
index 297a69f8dd..62c7ad1be3 100644
--- a/test/integration/generated/bodyString/src/models/parameters.ts
+++ b/test/integration/generated/bodyString/src/models/parameters.ts
@@ -21,6 +21,18 @@ export const $host: coreHttp.OperationURLParameter = {
   skipEncoding: true
 };
 
+export const contentType: coreHttp.OperationParameter = {
+  parameterPath: ["options", "contentType"],
+  mapper: {
+    defaultValue: "application/json",
+    serializedName: "Content-Type",
+    isConstant: true,
+    type: {
+      name: "String"
+    }
+  }
+};
+
 export const stringBody: coreHttp.OperationParameter = {
   parameterPath: ["options", "stringBody"],
   mapper: {
diff --git a/test/integration/generated/bodyString/src/operations/enum.ts b/test/integration/generated/bodyString/src/operations/enum.ts
index b496d79fef..e2b29fa35e 100644
--- a/test/integration/generated/bodyString/src/operations/enum.ts
+++ b/test/integration/generated/bodyString/src/operations/enum.ts
@@ -151,6 +151,7 @@ const putNotExpandableOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.stringBody5,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getReferencedOperationSpec: coreHttp.OperationSpec = {
@@ -184,6 +185,7 @@ const putReferencedOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.enumStringBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getReferencedConstantOperationSpec: coreHttp.OperationSpec = {
@@ -211,5 +213,6 @@ const putReferencedConstantOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.enumStringBody1,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
diff --git a/test/integration/generated/bodyString/src/operations/string.ts b/test/integration/generated/bodyString/src/operations/string.ts
index cc0fd8b3d0..5bd649098f 100644
--- a/test/integration/generated/bodyString/src/operations/string.ts
+++ b/test/integration/generated/bodyString/src/operations/string.ts
@@ -229,6 +229,7 @@ const putNullOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.stringBody,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getEmptyOperationSpec: coreHttp.OperationSpec = {
@@ -256,6 +257,7 @@ const putEmptyOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.stringBody1,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getMbcsOperationSpec: coreHttp.OperationSpec = {
@@ -283,6 +285,7 @@ const putMbcsOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.stringBody2,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getWhitespaceOperationSpec: coreHttp.OperationSpec = {
@@ -310,6 +313,7 @@ const putWhitespaceOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.stringBody3,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getNotProvidedOperationSpec: coreHttp.OperationSpec = {
@@ -365,6 +369,7 @@ const putBase64UrlEncodedOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.stringBody4,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getNullBase64UrlEncodedOperationSpec: coreHttp.OperationSpec = {
diff --git a/test/integration/generated/mediaTypes/src/mediaTypesClient.ts b/test/integration/generated/mediaTypes/src/mediaTypesClient.ts
index 3e8cc4573c..04fc99b782 100644
--- a/test/integration/generated/mediaTypes/src/mediaTypesClient.ts
+++ b/test/integration/generated/mediaTypes/src/mediaTypesClient.ts
@@ -12,8 +12,10 @@ import * as Models from "./models";
 import * as Mappers from "./models/mappers";
 import { MediaTypesClientContext } from "./mediaTypesClientContext";
 import {
-  MediaTypesClientAnalyzeBodyResponse,
-  MediaTypesClientAnalyzeBodyOptionalParams
+  ContentType,
+  MediaTypesClientAnalyzeBody$binaryOptionalParams,
+  MediaTypesClientAnalyzeBody$jsonOptionalParams,
+  MediaTypesClientAnalyzeBodyResponse
 } from "./models";
 
 class MediaTypesClient extends MediaTypesClientContext {
@@ -27,26 +29,51 @@ class MediaTypesClient extends MediaTypesClientContext {
 
   /**
    * Analyze body, that could be different media types.
+   * @param contentType Upload file type
    * @param options The options parameters.
    */
   analyzeBody(
-    options?: MediaTypesClientAnalyzeBodyOptionalParams
+    contentType: ContentType,
+    options?: MediaTypesClientAnalyzeBody$binaryOptionalParams
+  ): Promise<MediaTypesClientAnalyzeBodyResponse>;
+  /**
+   * Analyze body, that could be different media types.
+   * @param contentType Body Parameter content-type
+   * @param options The options parameters.
+   */
+  analyzeBody(
+    contentType: "application/json",
+    options?: MediaTypesClientAnalyzeBody$jsonOptionalParams
+  ): Promise<MediaTypesClientAnalyzeBodyResponse>;
+  /**
+   * Analyze body, that could be different media types.
+   * @param contentType Upload file type
+   * @param options The options parameters.
+   */
+  analyzeBody(
+    contentType: ContentType | "application/json",
+    options?:
+      | MediaTypesClientAnalyzeBody$binaryOptionalParams
+      | MediaTypesClientAnalyzeBody$jsonOptionalParams
   ): Promise<MediaTypesClientAnalyzeBodyResponse> {
     let operationSpec: coreHttp.OperationSpec;
     if (
-      options &&
-      "contentType" in options &&
       ["application/pdf", "image/jpeg", "image/png", "image/tiff"].indexOf(
-        options.contentType ?? ""
+        contentType
       ) > -1
     ) {
       operationSpec = analyzeBody$binaryOperationSpec;
-    } else {
+    } else if (["application/json"].indexOf(contentType) > -1) {
       operationSpec = analyzeBody$jsonOperationSpec;
+    } else {
+      throw new TypeError(
+        `"contentType" must be a valid value but instead was "${contentType}".`
+      );
     }
-    return this.sendOperationRequest({ options }, operationSpec) as Promise<
-      MediaTypesClientAnalyzeBodyResponse
-    >;
+    return this.sendOperationRequest(
+      { contentType, options },
+      operationSpec
+    ) as Promise<MediaTypesClientAnalyzeBodyResponse>;
   }
 }
 // Operation Specifications
@@ -76,6 +103,7 @@ const analyzeBody$jsonOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.input1,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType1],
   serializer
 };
 
diff --git a/test/integration/generated/mediaTypes/src/models/index.ts b/test/integration/generated/mediaTypes/src/models/index.ts
index cdec3d7896..85a82b90cf 100644
--- a/test/integration/generated/mediaTypes/src/models/index.ts
+++ b/test/integration/generated/mediaTypes/src/models/index.ts
@@ -32,10 +32,6 @@ export type ContentType =
  */
 export interface MediaTypesClientAnalyzeBody$binaryOptionalParams
   extends coreHttp.OperationOptions {
-  /**
-   * Upload file type
-   */
-  contentType?: ContentType;
   /**
    * Input parameter.
    */
@@ -53,13 +49,6 @@ export interface MediaTypesClientAnalyzeBody$jsonOptionalParams
   input?: SourcePath;
 }
 
-/**
- * Optional parameters.
- */
-export type MediaTypesClientAnalyzeBodyOptionalParams =
-  | MediaTypesClientAnalyzeBody$binaryOptionalParams
-  | MediaTypesClientAnalyzeBody$jsonOptionalParams;
-
 /**
  * Contains response data for the analyzeBody operation.
  */
diff --git a/test/integration/generated/mediaTypes/src/models/parameters.ts b/test/integration/generated/mediaTypes/src/models/parameters.ts
index c8442654aa..e21b790e2e 100644
--- a/test/integration/generated/mediaTypes/src/models/parameters.ts
+++ b/test/integration/generated/mediaTypes/src/models/parameters.ts
@@ -10,9 +10,10 @@ import * as coreHttp from "@azure/core-http";
 import * as Mappers from "../models/mappers";
 
 export const contentType: coreHttp.OperationParameter = {
-  parameterPath: ["options", "contentType"],
+  parameterPath: "contentType",
   mapper: {
     serializedName: "Content-Type",
+    required: true,
     type: {
       name: "Enum",
       allowedValues: [
@@ -35,6 +36,18 @@ export const input: coreHttp.OperationParameter = {
   }
 };
 
+export const contentType1: coreHttp.OperationParameter = {
+  parameterPath: "contentType",
+  mapper: {
+    defaultValue: "application/json",
+    serializedName: "Content-Type",
+    isConstant: true,
+    type: {
+      name: "String"
+    }
+  }
+};
+
 export const input1: coreHttp.OperationParameter = {
   parameterPath: ["options", "input"],
   mapper: Mappers.SourcePath
diff --git a/test/integration/generated/modelFlattening/src/modelFlatteningClient.ts b/test/integration/generated/modelFlattening/src/modelFlatteningClient.ts
index 5050c08c46..6a94ba8ea8 100644
--- a/test/integration/generated/modelFlattening/src/modelFlatteningClient.ts
+++ b/test/integration/generated/modelFlattening/src/modelFlatteningClient.ts
@@ -20,12 +20,12 @@ import {
   ModelFlatteningClientGetDictionaryResponse,
   ModelFlatteningClientPutResourceCollectionOptionalParams,
   ModelFlatteningClientGetResourceCollectionResponse,
-  ModelFlatteningClientPutSimpleProductResponse,
   ModelFlatteningClientPutSimpleProductOptionalParams,
-  ModelFlatteningClientPostFlattenedSimpleProductResponse,
+  ModelFlatteningClientPutSimpleProductResponse,
   ModelFlatteningClientPostFlattenedSimpleProductOptionalParams,
-  ModelFlatteningClientPutSimpleProductWithGroupingResponse,
-  ModelFlatteningClientPutSimpleProductWithGroupingOptionalParams
+  ModelFlatteningClientPostFlattenedSimpleProductResponse,
+  ModelFlatteningClientPutSimpleProductWithGroupingOptionalParams,
+  ModelFlatteningClientPutSimpleProductWithGroupingResponse
 } from "./models";
 
 class ModelFlatteningClient extends ModelFlatteningClientContext {
@@ -199,6 +199,7 @@ const putArrayOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.resourceArray,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getArrayOperationSpec: coreHttp.OperationSpec = {
@@ -234,6 +235,7 @@ const putWrappedArrayOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.resourceArray1,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getWrappedArrayOperationSpec: coreHttp.OperationSpec = {
@@ -267,6 +269,7 @@ const putDictionaryOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.resourceDictionary,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getDictionaryOperationSpec: coreHttp.OperationSpec = {
@@ -300,6 +303,7 @@ const putResourceCollectionOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.resourceComplexObject,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const getResourceCollectionOperationSpec: coreHttp.OperationSpec = {
@@ -329,6 +333,7 @@ const putSimpleProductOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.simpleBodyProduct,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const postFlattenedSimpleProductOperationSpec: coreHttp.OperationSpec = {
@@ -344,6 +349,7 @@ const postFlattenedSimpleProductOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.simpleBodyProduct1,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 const putSimpleProductWithGroupingOperationSpec: coreHttp.OperationSpec = {
@@ -359,6 +365,7 @@ const putSimpleProductWithGroupingOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.simpleBodyProduct2,
   urlParameters: [Parameters.$host, Parameters.name],
+  headerParameters: [Parameters.contentType],
   serializer
 };
 
diff --git a/test/integration/generated/modelFlattening/src/models/parameters.ts b/test/integration/generated/modelFlattening/src/models/parameters.ts
index 5c4d0e6dac..f68383fb7f 100644
--- a/test/integration/generated/modelFlattening/src/models/parameters.ts
+++ b/test/integration/generated/modelFlattening/src/models/parameters.ts
@@ -9,6 +9,18 @@
 import * as coreHttp from "@azure/core-http";
 import * as Mappers from "../models/mappers";
 
+export const contentType: coreHttp.OperationParameter = {
+  parameterPath: ["options", "contentType"],
+  mapper: {
+    defaultValue: "application/json",
+    serializedName: "Content-Type",
+    isConstant: true,
+    type: {
+      name: "String"
+    }
+  }
+};
+
 export const resourceArray: coreHttp.OperationParameter = {
   parameterPath: ["options", "resourceArray"],
   mapper: {
diff --git a/test/integration/generated/paging/src/operations/paging.ts b/test/integration/generated/paging/src/operations/paging.ts
index e602c0f6e5..8f26b37dd0 100644
--- a/test/integration/generated/paging/src/operations/paging.ts
+++ b/test/integration/generated/paging/src/operations/paging.ts
@@ -14,12 +14,12 @@ import {
   PagingGetNoItemNamePagesResponse,
   PagingGetNullNextLinkNamePagesResponse,
   PagingGetSinglePagesResponse,
-  PagingGetMultiplePagesResponse,
   PagingGetMultiplePagesOptionalParams,
-  PagingGetOdataMultiplePagesResponse,
+  PagingGetMultiplePagesResponse,
   PagingGetOdataMultiplePagesOptionalParams,
-  PagingGetMultiplePagesWithOffsetResponse,
+  PagingGetOdataMultiplePagesResponse,
   PagingGetMultiplePagesWithOffsetOptionalParams,
+  PagingGetMultiplePagesWithOffsetResponse,
   PagingGetMultiplePagesRetryFirstResponse,
   PagingGetMultiplePagesRetrySecondResponse,
   PagingGetSinglePagesFailureResponse,
@@ -27,25 +27,25 @@ import {
   PagingGetMultiplePagesFailureUriResponse,
   PagingGetMultiplePagesFragmentNextLinkResponse,
   PagingGetMultiplePagesFragmentWithGroupingNextLinkResponse,
-  PagingGetMultiplePagesLROResponse,
   PagingGetMultiplePagesLROOptionalParams,
+  PagingGetMultiplePagesLROResponse,
   PagingNextFragmentResponse,
   PagingNextFragmentWithGroupingResponse,
   PagingGetNoItemNamePagesNextResponse,
   PagingGetSinglePagesNextResponse,
-  PagingGetMultiplePagesNextResponse,
   PagingGetMultiplePagesNextOptionalParams,
-  PagingGetOdataMultiplePagesNextResponse,
+  PagingGetMultiplePagesNextResponse,
   PagingGetOdataMultiplePagesNextOptionalParams,
-  PagingGetMultiplePagesWithOffsetNextResponse,
+  PagingGetOdataMultiplePagesNextResponse,
   PagingGetMultiplePagesWithOffsetNextOptionalParams,
+  PagingGetMultiplePagesWithOffsetNextResponse,
   PagingGetMultiplePagesRetryFirstNextResponse,
   PagingGetMultiplePagesRetrySecondNextResponse,
   PagingGetSinglePagesFailureNextResponse,
   PagingGetMultiplePagesFailureNextResponse,
   PagingGetMultiplePagesFailureUriNextResponse,
-  PagingGetMultiplePagesLRONextResponse,
-  PagingGetMultiplePagesLRONextOptionalParams
+  PagingGetMultiplePagesLRONextOptionalParams,
+  PagingGetMultiplePagesLRONextResponse
 } from "../models";
 
 /**
diff --git a/test/integration/generated/report/src/reportClient.ts b/test/integration/generated/report/src/reportClient.ts
index 5ba602b57d..873d207a21 100644
--- a/test/integration/generated/report/src/reportClient.ts
+++ b/test/integration/generated/report/src/reportClient.ts
@@ -12,10 +12,10 @@ import * as Models from "./models";
 import * as Mappers from "./models/mappers";
 import { ReportClientContext } from "./reportClientContext";
 import {
-  ReportClientGetReportResponse,
   ReportClientGetReportOptionalParams,
-  ReportClientGetOptionalReportResponse,
-  ReportClientGetOptionalReportOptionalParams
+  ReportClientGetReportResponse,
+  ReportClientGetOptionalReportOptionalParams,
+  ReportClientGetOptionalReportResponse
 } from "./models";
 
 class ReportClient extends ReportClientContext {
diff --git a/test/integration/generated/xmlservice/src/models/parameters.ts b/test/integration/generated/xmlservice/src/models/parameters.ts
index 44436cb956..e012c2d992 100644
--- a/test/integration/generated/xmlservice/src/models/parameters.ts
+++ b/test/integration/generated/xmlservice/src/models/parameters.ts
@@ -22,6 +22,18 @@ export const $host: coreHttp.OperationURLParameter = {
   skipEncoding: true
 };
 
+export const contentType: coreHttp.OperationParameter = {
+  parameterPath: ["options", "contentType"],
+  mapper: {
+    defaultValue: "application/xml",
+    serializedName: "Content-Type",
+    isConstant: true,
+    type: {
+      name: "String"
+    }
+  }
+};
+
 export const model: coreHttp.OperationParameter = {
   parameterPath: "model",
   mapper: Mappers.RootWithRefAndNoMeta
@@ -147,6 +159,18 @@ export const properties1: coreHttp.OperationParameter = {
   }
 };
 
+export const contentType1: coreHttp.OperationParameter = {
+  parameterPath: ["options", "contentType"],
+  mapper: {
+    defaultValue: "application/json",
+    serializedName: "Content-Type",
+    isConstant: true,
+    type: {
+      name: "String"
+    }
+  }
+};
+
 export const properties2: coreHttp.OperationParameter = {
   parameterPath: "properties",
   mapper: Mappers.JsonInput
diff --git a/test/integration/generated/xmlservice/src/operations/xml.ts b/test/integration/generated/xmlservice/src/operations/xml.ts
index 14c0989c91..9ed25cd76f 100644
--- a/test/integration/generated/xmlservice/src/operations/xml.ts
+++ b/test/integration/generated/xmlservice/src/operations/xml.ts
@@ -475,6 +475,7 @@ const putComplexTypeRefNoMetaOperationSpec: coreHttp.OperationSpec = {
   responses: { 201: {} },
   requestBody: Parameters.model,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   isXML: true,
   contentType: "application/xml; charset=utf-8",
   serializer
@@ -497,6 +498,7 @@ const putComplexTypeRefWithMetaOperationSpec: coreHttp.OperationSpec = {
   responses: { 201: {} },
   requestBody: Parameters.model1,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   isXML: true,
   contentType: "application/xml; charset=utf-8",
   serializer
@@ -527,6 +529,7 @@ const putSimpleOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.slideshow,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   isXML: true,
   contentType: "application/xml; charset=utf-8",
   serializer
@@ -554,6 +557,7 @@ const putWrappedListsOperationSpec: coreHttp.OperationSpec = {
   },
   requestBody: Parameters.wrappedLists,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   isXML: true,
   contentType: "application/xml; charset=utf-8",
   serializer
@@ -587,6 +591,7 @@ const putEmptyListOperationSpec: coreHttp.OperationSpec = {
   responses: { 201: {} },
   requestBody: Parameters.slideshow,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   isXML: true,
   contentType: "application/xml; charset=utf-8",
   serializer
@@ -609,6 +614,7 @@ const putEmptyWrappedListsOperationSpec: coreHttp.OperationSpec = {
   responses: { 201: {} },
   requestBody: Parameters.appleBarrel,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   isXML: true,
   contentType: "application/xml; charset=utf-8",
   serializer
@@ -639,6 +645,7 @@ const putRootListOperationSpec: coreHttp.OperationSpec = {
   responses: { 201: {} },
   requestBody: Parameters.bananas,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   isXML: true,
   contentType: "application/xml; charset=utf-8",
   serializer
@@ -669,6 +676,7 @@ const putRootListSingleItemOperationSpec: coreHttp.OperationSpec = {
   responses: { 201: {} },
   requestBody: Parameters.bananas,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   isXML: true,
   contentType: "application/xml; charset=utf-8",
   serializer
@@ -699,6 +707,7 @@ const putEmptyRootListOperationSpec: coreHttp.OperationSpec = {
   responses: { 201: {} },
   requestBody: Parameters.bananas,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   isXML: true,
   contentType: "application/xml; charset=utf-8",
   serializer
@@ -721,6 +730,7 @@ const putEmptyChildElementOperationSpec: coreHttp.OperationSpec = {
   responses: { 201: {} },
   requestBody: Parameters.banana,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   isXML: true,
   contentType: "application/xml; charset=utf-8",
   serializer
@@ -758,6 +768,7 @@ const putServicePropertiesOperationSpec: coreHttp.OperationSpec = {
   requestBody: Parameters.properties,
   queryParameters: [Parameters.comp1, Parameters.restype],
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   isXML: true,
   contentType: "application/xml; charset=utf-8",
   serializer
@@ -793,6 +804,7 @@ const putAclsOperationSpec: coreHttp.OperationSpec = {
   requestBody: Parameters.properties1,
   queryParameters: [Parameters.comp2, Parameters.restype1],
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType],
   isXML: true,
   contentType: "application/xml; charset=utf-8",
   serializer
@@ -816,6 +828,7 @@ const jsonInputOperationSpec: coreHttp.OperationSpec = {
   responses: { 200: {} },
   requestBody: Parameters.properties2,
   urlParameters: [Parameters.$host],
+  headerParameters: [Parameters.contentType1],
   serializer
 };
 const jsonOutputOperationSpec: coreHttp.OperationSpec = {
diff --git a/test/integration/mediaType.spec.ts b/test/integration/mediaType.spec.ts
index 6bf5f58b44..d2b6c1f743 100644
--- a/test/integration/mediaType.spec.ts
+++ b/test/integration/mediaType.spec.ts
@@ -31,8 +31,7 @@ describe("Integration tests for MediaTypes", () => {
 
   describe("#analyzeBody", () => {
     it("works with binary content type", async () => {
-      const response = await client.analyzeBody({
-        contentType: "application/pdf",
+      const response = await client.analyzeBody("application/pdf", {
         input: "PDF"
       });
 
@@ -47,7 +46,7 @@ describe("Integration tests for MediaTypes", () => {
     });
 
     it("works with json content type", async () => {
-      const response = await client.analyzeBody({
+      const response = await client.analyzeBody("application/json", {
         input: { source: "foo" }
       });