my code is below not get string value

Sorry, there is no enough info in your question. I'm happy with tm being your object, but that's not really a precious piece of info. Do you mean tm is an instance of a class you have written? Then you should, please, provide the code of the Server_Conn method, in order to shed some light on such a obscure question.

The question makes no sense. We have no idea what is tm and tm.Server_Conn. If this is your method, you return null, no one else.
Due to long today's rain, my access to your hard drive is somewhat limited.
—SA