Move *CommaSeperatedValues APIs from IHeaderDictionary to extension.

src/Microsoft.AspNet.Http.Abstractions/IHeaderDictionary.cs

@@ -30,34 +30,5 @@ public interface IHeaderDictionary : IReadableStringCollection, IDictionary<stri
         /// Gets a collection containing the keys.
         /// </summary>
         new ICollection<string> Keys { get; }
-
-        /// <summary>
-        /// Get the associated values from the collection separated into individual values.
-        /// Quoted values will not be split, and the quotes will be removed.
-        /// </summary>
-        /// <param name="key">The header name.</param>
-        /// <returns>the associated values from the collection separated into individual values, or null if the key is not present.</returns>
-        StringValues GetCommaSeparatedValues(string key);
-
-        /// <summary>
-        /// Add a new value. Appends to the header list if already present
-        /// </summary>
-        /// <param name="key">The header name.</param>
-        /// <param name="value">The header value.</param>
-        void Append(string key, StringValues value);
-
-        /// <summary>
-        /// Quotes any values containing comas, and then coma joins all of the values with any existing values.
-        /// </summary>
-        /// <param name="key">The header name.</param>
-        /// <param name="values">The header values.</param>
-        void AppendCommaSeparatedValues(string key, params string[] values);
-
-        /// <summary>
-        /// Quotes any values containing comas, and then coma joins all of the values.
-        /// </summary>
-        /// <param name="key">The header name.</param>
-        /// <param name="values">The header values.</param>
-        void SetCommaSeparatedValues(string key, params string[] values);
     }
 }

src/Microsoft.AspNet.Http.Extensions/HeaderDictionaryExtensions.cs

@@ -0,0 +1,52 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNet.Http.Internal;
+using Microsoft.Framework.Primitives;
+
+namespace Microsoft.AspNet.Http
+{
+    public static class HeaderDictionaryExtensions
+    {
+        /// <summary>
+        /// Add new values. Each item remains a separate array entry.
+        /// </summary>
+        /// <param name="key">The header name.</param>
+        /// <param name="value">The header value.</param>
+        public static void Append(this IHeaderDictionary headers, string key, StringValues value)
+        {
+            ParsingHelpers.AppendHeaderUnmodified(headers, key, value);
+        }
+
+        /// <summary>
+        /// Quotes any values containing comas, and then coma joins all of the values with any existing values.
+        /// </summary>
+        /// <param name="key">The header name.</param>
+        /// <param name="values">The header values.</param>
+        public static void AppendCommaSeparatedValues(this IHeaderDictionary headers, string key, params string[] values)
+        {
+            ParsingHelpers.AppendHeaderJoined(headers, key, values);
+        }
+
+        /// <summary>
+        /// Get the associated values from the collection separated into individual values.
+        /// Quoted values will not be split, and the quotes will be removed.
+        /// </summary>
+        /// <param name="key">The header name.</param>
+        /// <returns>the associated values from the collection separated into individual values, or StringValues.Empty if the key is not present.</returns>
+        public static string[] GetCommaSeparatedValues(this IHeaderDictionary headers, string key)
+        {
+            return ParsingHelpers.GetHeaderSplit(headers, key);
+        }
+
+        /// <summary>
+        /// Quotes any values containing comas, and then coma joins all of the values.
+        /// </summary>
+        /// <param name="key">The header name.</param>
+        /// <param name="values">The header values.</param>
+        public static void SetCommaSeparatedValues(this IHeaderDictionary headers, string key, params string[] values)
+        {
+            ParsingHelpers.SetHeaderJoined(headers, key, values);
+        }
+    }
+}