Add strong and weak ETag comparisons

Author: JunTaoLuo

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

@@ -103,7 +103,7 @@ public override bool Equals(object obj)
             }
 
             // Since the tag is a quoted-string we treat it case-sensitive.
-            return ((_isWeak == other._isWeak) && (string.CompareOrdinal(_tag, other._tag) == 0));
+            return _isWeak == other._isWeak && string.Equals(_tag, other._tag);
         }
 
         public override int GetHashCode()
@@ -112,6 +112,24 @@ public override int GetHashCode()
             return _tag.GetHashCode() ^ _isWeak.GetHashCode();
         }
 
+        public static bool CompareStrongly(EntityTagHeaderValue left, EntityTagHeaderValue right)
+        {
+            if (left == null || right == null)
+            {
+                return false;
+            }
+            return !left.IsWeak && !right.IsWeak && string.Equals(left.Tag, right.Tag);
+        }
+
+        public static bool CompareWeakly(EntityTagHeaderValue left, EntityTagHeaderValue right)
+        {
+            if (left == null || right == null)
+            {
+                return false;
+            }
+            return string.Equals(left.Tag, right.Tag);
+        }
+
         public static EntityTagHeaderValue Parse(string input)
         {
             var index = 0;

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

@@ -99,6 +99,52 @@ public void Equals_UseSameAndDifferentETags_EqualOrNotEqualNoExceptions()
             Assert.True(etag1.Equals(etag5), "tag vs. tag..");
         }
 
+        [Fact]
+        public void CompareStrongly_UseSameAndDifferentETags_EqualOrNotEqualNoExceptions()
+        {
+            var etag1 = new EntityTagHeaderValue("\"tag\"");
+            var etag2 = new EntityTagHeaderValue("\"TAG\"");
+            var etag3 = new EntityTagHeaderValue("\"tag\"", true);
+            var etag4 = new EntityTagHeaderValue("\"tag1\"");
+            var etag5 = new EntityTagHeaderValue("\"tag\"");
+            var etag6 = EntityTagHeaderValue.Any;
+
+            Assert.False(EntityTagHeaderValue.CompareStrongly(etag1, etag2), "Different casing.");
+            Assert.False(EntityTagHeaderValue.CompareStrongly(etag2, etag1), "Different casing.");
+            Assert.False(EntityTagHeaderValue.CompareStrongly(etag1, null), "tag vs. <null>.");
+            Assert.False(EntityTagHeaderValue.CompareStrongly(null, etag1), "<null> vs tag.");
+            Assert.False(EntityTagHeaderValue.CompareStrongly(null, null), "<null> vs. <null>.");
+            Assert.False(EntityTagHeaderValue.CompareStrongly(etag3, etag3), "weak vs. weak.");
+            Assert.False(EntityTagHeaderValue.CompareStrongly(etag1, etag3), "strong vs. weak.");
+            Assert.False(EntityTagHeaderValue.CompareStrongly(etag3, etag1), "weak vs. strong.");
+            Assert.False(EntityTagHeaderValue.CompareStrongly(etag1, etag4), "tag vs. tag1.");
+            Assert.False(EntityTagHeaderValue.CompareStrongly(etag1, etag6), "tag vs. *.");
+            Assert.True(EntityTagHeaderValue.CompareStrongly(etag1, etag5), "tag vs. tag.");
+        }
+
+        [Fact]
+        public void CompareWeakly_UseSameAndDifferentETags_EqualOrNotEqualNoExceptions()
+        {
+            var etag1 = new EntityTagHeaderValue("\"tag\"");
+            var etag2 = new EntityTagHeaderValue("\"TAG\"");
+            var etag3 = new EntityTagHeaderValue("\"tag\"", true);
+            var etag4 = new EntityTagHeaderValue("\"tag1\"");
+            var etag5 = new EntityTagHeaderValue("\"tag\"");
+            var etag6 = EntityTagHeaderValue.Any;
+
+            Assert.False(EntityTagHeaderValue.CompareWeakly(etag1, etag2), "Different casing.");
+            Assert.False(EntityTagHeaderValue.CompareWeakly(etag2, etag1), "Different casing.");
+            Assert.False(EntityTagHeaderValue.CompareWeakly(etag1, null), "tag vs. <null>.");
+            Assert.False(EntityTagHeaderValue.CompareWeakly(null, etag1), "<null> vs tag.");
+            Assert.False(EntityTagHeaderValue.CompareWeakly(null, null), "<null> vs. <null>.");
+            Assert.True(EntityTagHeaderValue.CompareWeakly(etag3, etag3), "weak vs. weak.");
+            Assert.True(EntityTagHeaderValue.CompareWeakly(etag1, etag3), "strong vs. weak.");
+            Assert.True(EntityTagHeaderValue.CompareWeakly(etag3, etag1), "weak vs. strong.");
+            Assert.False(EntityTagHeaderValue.CompareWeakly(etag1, etag4), "tag vs. tag1.");
+            Assert.False(EntityTagHeaderValue.CompareWeakly(etag1, etag6), "tag vs. *.");
+            Assert.True(EntityTagHeaderValue.CompareWeakly(etag1, etag5), "tag vs. tag.");
+        }
+
         [Fact]
         public void Parse_SetOfValidValueStrings_ParsedCorrectly()
         {