mssql query, set non xml data size

I try to convert a few table(MSSQL) into an xml file. the result has been truncated at 2.7 MB (just 2KB before the end).

If I increase the "non xml data" size and "xml data" size in the vs express(SQL>execution settings>query options...>resutls>grid> "non xml data" and "xml data") then I get the exact result

So the query is working fine.

Only problem, I need this in a program(c#) not in the query window.

I use executexmlreader.

Someone has any ideal, what can be wrong?

        SqlConnection testConnection = new SqlConnection();
        testConnection.ConnectionString = @"Data Source=.\SQLEXPRESS;Integrated Security=True;Connect Timeout=30;";
        testConnection.Open();

        TestCommand = new SqlCommand("exec prAdvListToXML", testConnection);

        XmlReader TestXmlReader = TestCommand.ExecuteXmlReader();
        XmlWriter TestFileWriter = XmlWriter.Create(@"C:\temp\output.xml");
        TestFileWriter.WriteProcessingInstruction("xml", "version='1.0' encoding='UTF-16'");

        TestFileWriter.WriteNode(TestXmlReader, true);