#360 Add Response.Clear() extension.

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

@@ -0,0 +1,26 @@
+// 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 System;
+using Microsoft.AspNet.Http.Features;
+
+namespace Microsoft.AspNet.Http.Extensions
+{
+    public static class ResponseExtensions
+    {
+        public static void Clear(this HttpResponse response)
+        {
+            if (response.HasStarted)
+            {
+                throw new InvalidOperationException("The response cannot be cleared, it has already started sending.");
+            }
+            response.StatusCode = 200;
+            response.HttpContext.Features.Get<IHttpResponseFeature>().ReasonPhrase = null;
+            response.Headers.Clear();
+            if (response.Body.CanSeek)
+            {
+                response.Body.SetLength(0);
+            }
+        }
+    }
+}

test/Microsoft.AspNet.Http.Extensions.Tests/ResponseExtensionTests.cs

@@ -0,0 +1,64 @@
+// 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 System;
+using System.Collections.Generic;
+using System.IO;
+using System.Threading.Tasks;
+using Microsoft.AspNet.Http.Features;
+using Microsoft.AspNet.Http.Internal;
+using Microsoft.Framework.Primitives;
+using Xunit;
+
+namespace Microsoft.AspNet.Http.Extensions
+{
+    public class ResponseExtensionTests
+    {
+        [Fact]
+        public void Clear_ResetsResponse()
+        {
+            var context = new DefaultHttpContext();
+            context.Response.StatusCode = 201;
+            context.Response.Headers["custom"] = "value";
+            context.Response.Body.Write(new byte[100], 0, 100);
+
+            context.Response.Clear();
+
+            Assert.Equal(200, context.Response.StatusCode);
+            Assert.Equal(string.Empty, context.Response.Headers["custom"].ToString());
+            Assert.Equal(0, context.Response.Body.Length);
+        }
+
+        [Fact]
+        public void Clear_AlreadyStarted_Throws()
+        {
+            var context = new DefaultHttpContext();
+            context.Features.Set<IHttpResponseFeature>(new StartedResponseFeature());
+
+            Assert.Throws<InvalidOperationException>(() => context.Response.Clear());
+        }
+
+        private class StartedResponseFeature : IHttpResponseFeature
+        {
+            public Stream Body { get; set; }
+
+            public bool HasStarted { get { return true; } }
+
+            public IDictionary<string, StringValues> Headers { get; set; }
+
+            public string ReasonPhrase { get; set; }
+
+            public int StatusCode { get; set; }
+
+            public void OnCompleted(Func<object, Task> callback, object state)
+            {
+                throw new NotImplementedException();
+            }
+
+            public void OnStarting(Func<object, Task> callback, object state)
+            {
+                throw new NotImplementedException();
+            }
+        }
+    }
+}