DTD as Embedded Resource To Validate XML

I'm getting an error message of: 

  HResult=-2146232000
  Message=Cannot have multiple DTDs. Line 2, position 1.
  Source=System.Xml
  LineNumber=2

When I try to use my embedded DTD to validate an XML file.

I looked at  Validate xml through the embedded resource DTD, and am using the same basic method, but it seems they don't get the same error I do.

I load the DTD add it to the parser context: 

            XmlParserContext parserContext = new XmlParserContext(nameTable, new XmlNamespaceManager(nameTable), "MyDocType", null, null, dtd, "file:///"+AppDomain.CurrentDomain.BaseDirectory.Replace('\\', '/'), null, XmlSpace.None);

And even set the base URI to match the searchpath given for the DTD when I don't include the context so that it might match the DTD referenced and the DTD provided in the context.

The XML contains: 

<!DOCTYPE MyDocType SYSTEM "MyDocType.dtd">

What am I doing wrong here?

How can I get the DTD reference to match the one I have as my embedded resource?

Thanks!
-Baron