Include the oneof-case in equality and hash code generated code.

The included C# test will fail until the regenerated code is used, which is in the next commit.

csharp/src/Google.Protobuf.Test/GeneratedMessageTest.cs

@@ -565,6 +565,16 @@ namespace Google.Protobuf
             Assert.AreEqual(TestAllTypes.OneofFieldOneofCase.None, message.OneofFieldCase);
         }
 
+        [Test]
+        public void Oneof_DefaultValuesNotEqual()
+        {
+            var message1 = new TestAllTypes { OneofString = "" };
+            var message2 = new TestAllTypes { OneofUint32 = 0 };
+            Assert.AreEqual(TestAllTypes.OneofFieldOneofCase.OneofString, message1.OneofFieldCase);
+            Assert.AreEqual(TestAllTypes.OneofFieldOneofCase.OneofUint32, message2.OneofFieldCase);
+            Assert.AreNotEqual(message1, message2);
+        }
+
         [Test]
         public void OneofSerialization_NonDefaultValue()
         {

src/google/protobuf/compiler/csharp/csharp_message.cc

@@ -323,6 +323,10 @@ void MessageGenerator::GenerateFrameworkMethods(io::Printer* printer) {
             CreateFieldGeneratorInternal(descriptor_->field(i)));
         generator->WriteEquals(printer);
     }
+    for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
+        printer->Print("if ($property_name$Case != other.$property_name$Case) return false;\n",
+            "property_name", UnderscoresToCamelCase(descriptor_->oneof_decl(i)->name(), true));
+    }
     printer->Outdent();
     printer->Print(
         "  return true;\n"
@@ -339,6 +343,10 @@ void MessageGenerator::GenerateFrameworkMethods(io::Printer* printer) {
             CreateFieldGeneratorInternal(descriptor_->field(i)));
         generator->WriteHash(printer);
     }
+    for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
+        printer->Print("hash ^= (int) $name$Case_;\n",
+            "name", UnderscoresToCamelCase(descriptor_->oneof_decl(i)->name(), false));
+    }
     printer->Print("return hash;\n");
     printer->Outdent();
     printer->Print("}\n\n");