diff --git a/src/Microsoft.OpenApi/Models/OpenApiComponents.cs b/src/Microsoft.OpenApi/Models/OpenApiComponents.cs
index 0db85ed77..5b43b5187 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiComponents.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiComponents.cs
@@ -318,7 +318,7 @@ private void RenderComponents(IOpenApiWriter writer, Action<IOpenApiWriter, IOpe
         {
             var loops = writer.GetSettings().LoopDetector.Loops;
             writer.WriteStartObject();
-            if (loops.TryGetValue(typeof(OpenApiSchema), out List<object> schemas))
+            if (loops.TryGetValue(typeof(OpenApiSchema), out var schemas))
             {
                 writer.WriteOptionalMap(OpenApiConstants.Schemas, Schemas, callback);
             }
diff --git a/src/Microsoft.OpenApi/Models/OpenApiDocument.cs b/src/Microsoft.OpenApi/Models/OpenApiDocument.cs
index 27296f47b..cf7e53cae 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiDocument.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiDocument.cs
@@ -238,7 +238,7 @@ public void SerializeAsV2(IOpenApiWriter writer)
             {
                 var loops = writer.GetSettings().LoopDetector.Loops;
 
-                if (loops.TryGetValue(typeof(OpenApiSchema), out List<object> schemas))
+                if (loops.TryGetValue(typeof(OpenApiSchema), out var schemas))
                 {
                     var openApiSchemas = schemas.Cast<OpenApiSchema>().Distinct().ToList()
                          .ToDictionary<OpenApiSchema, string>(k => k.Reference.Id);
@@ -409,14 +409,15 @@ private static void WriteHostInfoV2(IOpenApiWriter writer, IList<OpenApiServer>?
                         return url;
                     })
                 .Where(
-                    u => Uri.Compare(
+                    u => u is not null &&
+                        Uri.Compare(
                             u,
                             firstServerUrl,
                             UriComponents.Host | UriComponents.Port | UriComponents.Path,
                             UriFormat.SafeUnescaped,
                             StringComparison.OrdinalIgnoreCase) ==
                         0 && u.IsAbsoluteUri)
-                .Select(u => u.Scheme)
+                .Select(u => u!.Scheme)
                 .Distinct()
                 .ToList();
 
@@ -464,10 +465,12 @@ public async Task<string> GetHashCodeAsync(CancellationToken cancellationToken =
             SerializeAsV3(openApiJsonWriter);
             await openApiJsonWriter.FlushAsync(cancellationToken).ConfigureAwait(false);
 
+#if NET5_0_OR_GREATER
+            await cryptoStream.FlushFinalBlockAsync(cancellationToken).ConfigureAwait(false);
+#else
             cryptoStream.FlushFinalBlock();
-            var hash = sha.Hash;
-
-            return ConvertByteArrayToString(hash);
+#endif
+            return ConvertByteArrayToString(sha.Hash ?? []);
         }
 
         private static string ConvertByteArrayToString(byte[] hash)
diff --git a/src/Microsoft.OpenApi/Models/OpenApiOperation.cs b/src/Microsoft.OpenApi/Models/OpenApiOperation.cs
index 6182eda2b..f5fe32274 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiOperation.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiOperation.cs
@@ -283,11 +283,11 @@ public void SerializeAsV2(IOpenApiWriter writer)
             {
                 var produces = Responses
                     .Where(static r => r.Value.Content != null)
-                    .SelectMany(static r => r.Value.Content?.Keys)
+                    .SelectMany(static r => r.Value.Content?.Keys ?? [])
                     .Concat(
                         Responses
                         .Where(static r => r.Value.Reference is {HostDocument: not null})
-                        .SelectMany(static r => r.Value.Content?.Keys))
+                        .SelectMany(static r => r.Value.Content?.Keys ?? []))
                     .Distinct(StringComparer.OrdinalIgnoreCase)
                     .ToArray();
 
diff --git a/src/Microsoft.OpenApi/Reader/OpenApiModelFactory.cs b/src/Microsoft.OpenApi/Reader/OpenApiModelFactory.cs
index 31b939548..fea86f899 100644
--- a/src/Microsoft.OpenApi/Reader/OpenApiModelFactory.cs
+++ b/src/Microsoft.OpenApi/Reader/OpenApiModelFactory.cs
@@ -129,7 +129,11 @@ public static async Task<ReadResult> LoadAsync(Stream input, string format = nul
                 var result = await InternalLoadAsync(preparedStream, format, settings, cancellationToken).ConfigureAwait(false);
                 if (!settings.LeaveStreamOpen)
                 {
+#if NETSTANDARD2_1_OR_GREATER || NETCOREAPP || NET5_0_OR_GREATER
+                    await input.DisposeAsync().ConfigureAwait(false);
+#else
                     input.Dispose();
+#endif
                 }
                 return result;
             }