Add encoder extension methods

src/Microsoft.AspNet.Http.Extensions/Encoders/EncoderExtensions.cs

@@ -0,0 +1,51 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using Microsoft.AspNet.Http;
+using Microsoft.Framework.DependencyInjection;
+
+namespace Microsoft.AspNet.WebUtilities.Encoders
+{
+    /// <summary>
+    /// Contains extension methods for fetching encoders from a service provider.
+    /// </summary>
+    public static class EncoderExtensions
+    {
+        /// <summary>
+        /// Retrieves an IHtmlEncoder from a service provider.
+        /// </summary>
+        /// <remarks>
+        /// This method is guaranteed never to return null.
+        /// It will return a default encoder instance if the service provider does not contain one.
+        /// </remarks>
+        public static IHtmlEncoder GetHtmlEncoder([NotNull] this IServiceProvider serviceProvider)
+        {
+            return serviceProvider.GetService<IHtmlEncoder>() ?? HtmlEncoder.Default;
+        }
+
+        /// <summary>
+        /// Retrieves an IJavaScriptStringEncoder from a service provider.
+        /// </summary>
+        /// <remarks>
+        /// This method is guaranteed never to return null.
+        /// It will return a default encoder instance if the service provider does not contain one.
+        /// </remarks>
+        public static IJavaScriptStringEncoder GetJavaScriptStringEncoder([NotNull] this IServiceProvider serviceProvider)
+        {
+            return serviceProvider.GetService<IJavaScriptStringEncoder>() ?? JavaScriptStringEncoder.Default;
+        }
+
+        /// <summary>
+        /// Retrieves an IUrlEncoder from a service provider.
+        /// </summary>
+        /// <remarks>
+        /// This method is guaranteed never to return null.
+        /// It will return a default encoder instance if the service provider does not contain one.
+        /// </remarks>
+        public static IUrlEncoder GetUrlEncoder([NotNull] this IServiceProvider serviceProvider)
+        {
+            return serviceProvider.GetService<IUrlEncoder>() ?? UrlEncoder.Default;
+        }
+    }
+}