Addressed pranav's code review comments.

Author: N. Taylor Mullen

src/Microsoft.AspNet.Mvc.TagHelpers/TagHelperOutputExtensions.cs

@@ -30,13 +30,12 @@ public static void CopyHtmlAttribute(this TagHelperOutput tagHelperOutput,
                                              TagHelperContext context)
         {
             // We look for the original attribute so we can restore the exact attribute name the user typed.
-            var entry = context.AllAttributes.Single(attribute =>
+            var entry = context.AllAttributes.First(attribute =>
                 attribute.Key.Equals(attributeName, StringComparison.OrdinalIgnoreCase));
-            var originalAttribute = new KeyValuePair<string, string>(entry.Key, entry.Value.ToString());
 
-            if (!tagHelperOutput.Attributes.ContainsKey(originalAttribute.Key))
+            if (!tagHelperOutput.Attributes.ContainsKey(entry.Key))
             {
-                tagHelperOutput.Attributes.Add(originalAttribute);
+                tagHelperOutput.Attributes.Add(entry.Key, entry.Value.ToString());
             }
         }
 

test/Microsoft.AspNet.Mvc.TagHelpers.Test/TagHelperOutputExtensionsTest.cs

@@ -1,6 +1,7 @@
 // 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 System.Collections.Generic;
 using System.Linq;
 using Microsoft.AspNet.Mvc.Rendering;
@@ -22,7 +23,7 @@ public void CopyHtmlAttribute_CopiesOriginalAttributes(string attributeName, str
                 attributes: new Dictionary<string, string>(),
                 content: string.Empty);
             var tagHelperContext = new TagHelperContext(
-                new Dictionary<string, object>()
+                new Dictionary<string, object>(StringComparer.Ordinal)
                 {
                     { attributeName, attributeValue }
                 });
@@ -43,14 +44,14 @@ public void CopyHtmlAttribute_DoesntOverrideAttributes()
             var attributeName = "hello";
             var tagHelperOutput = new TagHelperOutput(
                 "p",
-                attributes: new Dictionary<string, string>
+                attributes: new Dictionary<string, string>()
                 {
                     { attributeName, "world2" }
                 },
                 content: string.Empty);
             var expectedAttribute = new KeyValuePair<string, string>(attributeName, "world2");
             var tagHelperContext = new TagHelperContext(
-                new Dictionary<string, object>()
+                new Dictionary<string, object>(StringComparer.Ordinal)
                 {
                     { attributeName, "world" }
                 });