Fix issue 10 - check serialized size before writing to stream
diff --git a/src/ProtocolBuffers.Test/TestProtos/UnitTestCSharpOptionsProtoFile.cs b/src/ProtocolBuffers.Test/TestProtos/UnitTestCSharpOptionsProtoFile.cs
index 96ee642..341dcb2 100644
--- a/src/ProtocolBuffers.Test/TestProtos/UnitTestCSharpOptionsProtoFile.cs
+++ b/src/ProtocolBuffers.Test/TestProtos/UnitTestCSharpOptionsProtoFile.cs
@@ -110,6 +110,7 @@
     }
     
     public override void WriteTo(pb::CodedOutputStream output) {
+      int size = SerializedSize;
       if (HasNormal) {
         output.WriteString(1, Normal);
       }