Fixes to ByteString's equality handling.

csharp/src/ProtocolBuffers.Test/ByteStringTest.cs

@@ -38,6 +38,32 @@ namespace Google.Protobuf
 {
     public class ByteStringTest
     {
+        [Test]
+        public void Equality()
+        {
+            ByteString b1 = ByteString.CopyFrom(1, 2, 3);
+            ByteString b2 = ByteString.CopyFrom(1, 2, 3);
+            ByteString b3 = ByteString.CopyFrom(1, 2, 4);
+            ByteString b4 = ByteString.CopyFrom(1, 2, 3, 4);
+            EqualityTester.AssertEquality(b1, b1);
+            EqualityTester.AssertEquality(b1, b2);
+            EqualityTester.AssertInequality(b1, b3);
+            EqualityTester.AssertInequality(b1, b4);
+            EqualityTester.AssertInequality(b1, null);
+            Assert.IsTrue(b1 == b1);
+            Assert.IsTrue(b1 == b2);
+            Assert.IsFalse(b1 == b3);
+            Assert.IsFalse(b1 == b4);
+            Assert.IsFalse(b1 == null);
+            Assert.IsTrue((ByteString) null == null);
+            Assert.IsFalse(b1 != b1);
+            Assert.IsFalse(b1 != b2);
+            Assert.IsTrue(b1 != b3);
+            Assert.IsTrue(b1 != b4);
+            Assert.IsTrue(b1 != null);
+            Assert.IsFalse((ByteString) null != null);
+        }
+
         [Test]
         public void EmptyByteStringHasZeroSize()
         {

csharp/src/ProtocolBuffers/ByteString.cs

@@ -212,11 +212,22 @@ namespace Google.Protobuf
             {
                 return true;
             }
-            if (ReferenceEquals(lhs, null))
+            if (ReferenceEquals(lhs, null) || ReferenceEquals(rhs, null))
             {
                 return false;
             }
-            return lhs.Equals(rhs);
+            if (lhs.bytes.Length != rhs.bytes.Length)
+            {
+                return false;
+            }
+            for (int i = 0; i < lhs.Length; i++)
+            {
+                if (rhs.bytes[i] != lhs.bytes[i])
+                {
+                    return false;
+                }
+            }
+            return true;
         }
 
         public static bool operator !=(ByteString lhs, ByteString rhs)
@@ -228,12 +239,7 @@ namespace Google.Protobuf
 
         public override bool Equals(object obj)
         {
-            ByteString other = obj as ByteString;
-            if (obj == null)
-            {
-                return false;
-            }
-            return Equals(other);
+            return this == (obj as ByteString);
         }
 
         public override int GetHashCode()
@@ -248,18 +254,7 @@ namespace Google.Protobuf
 
         public bool Equals(ByteString other)
         {
-            if (other.bytes.Length != bytes.Length)
-            {
-                return false;
-            }
-            for (int i = 0; i < bytes.Length; i++)
-            {
-                if (other.bytes[i] != bytes[i])
-                {
-                    return false;
-                }
-            }
-            return true;
+            return this == other;
         }
 
         /// <summary>