#177 Enable Copy to return non-read-only.

src/Microsoft.Net.Http.Headers/MediaTypeHeaderValue.cs

@@ -273,11 +273,6 @@ namespace Microsoft.Net.Http.Headers
         /// <returns>A deep copy.</returns>
         public MediaTypeHeaderValue Copy()
         {
-            if (IsReadOnly)
-            {
-                return this;
-            }
-
             var other = new MediaTypeHeaderValue();
             other._mediaType = _mediaType;
 

src/Microsoft.Net.Http.Headers/NameValueHeaderValue.cs

@@ -64,11 +64,6 @@ namespace Microsoft.Net.Http.Headers
         /// <returns>A copy.</returns>
         public NameValueHeaderValue Copy()
         {
-            if (IsReadOnly)
-            {
-                return this;
-            }
-
             return new NameValueHeaderValue()
             {
                 _name = _name,

test/Microsoft.Net.Http.Headers.Tests/MediaTypeHeaderValueTest.cs

@@ -135,6 +135,29 @@ namespace Microsoft.Net.Http.Headers
             Assert.Same(pair0.Value, pair1.Value);
         }
 
+        [Fact]
+        public void CopyFromReadOnly_WithParameters_CopiedAsNonReadOnly()
+        {
+            var mediaType0 = new MediaTypeHeaderValue("text/plain");
+            mediaType0.Parameters.Add(new NameValueHeaderValue("name", "value"));
+            var mediaType1 = mediaType0.CopyAsReadOnly();
+            var mediaType2 = mediaType1.Copy();
+
+            Assert.NotSame(mediaType2, mediaType1);
+            Assert.Same(mediaType2.MediaType, mediaType1.MediaType);
+            Assert.True(mediaType1.IsReadOnly);
+            Assert.False(mediaType2.IsReadOnly);
+            Assert.NotSame(mediaType2.Parameters, mediaType1.Parameters);
+            Assert.Equal(mediaType2.Parameters.Count, mediaType1.Parameters.Count);
+            var pair2 = mediaType2.Parameters.First();
+            var pair1 = mediaType1.Parameters.First();
+            Assert.NotSame(pair2, pair1);
+            Assert.True(pair1.IsReadOnly);
+            Assert.False(pair2.IsReadOnly);
+            Assert.Same(pair2.Name, pair1.Name);
+            Assert.Same(pair2.Value, pair1.Value);
+        }
+
         [Fact]
         public void MediaType_SetAndGetMediaType_MatchExpectations()
         {

test/Microsoft.Net.Http.Headers.Tests/NameValueHeaderValueTest.cs

@@ -127,6 +127,22 @@ namespace Microsoft.Net.Http.Headers
             Assert.Throws<InvalidOperationException>(() => { pair1.Value = "othervalue"; });
         }
 
+        [Fact]
+        public void CopyFromReadOnly_NameAndValue_CopiedAsNonReadOnly()
+        {
+            var pair0 = new NameValueHeaderValue("name", "value");
+            var pair1 = pair0.CopyAsReadOnly();
+            var pair2 = pair1.Copy();
+            Assert.NotSame(pair0, pair1);
+            Assert.Same(pair0.Name, pair1.Name);
+            Assert.Same(pair0.Value, pair1.Value);
+
+            // Change one value and verify the other is unchanged.
+            pair2.Value = "othervalue";
+            Assert.Equal("othervalue", pair2.Value);
+            Assert.Equal("value", pair1.Value);
+        }
+
         [Fact]
         public void Value_CallSetterWithInvalidValues_Throw()
         {