Problem with running method from orchestration

Hello,

I have a simple orchestration with 3 shapes, a Receive, Send and an Expression shape. Also I got a class with a simple method that just writes a line to a text file. The class has a strong name and I installed it into GAC with gacutil. Also I’ve added the reference of the class.
The problem is that when I run the orchestration, I put some file in the input folder (the pipelines are passthru), the file disappears and that’s it, no further actions. The file does not appear in the output folder and there are no any actions from my method, also there are no errors or exceptions in Administration Console.
But if I delete the Expression shape, leaving just Receive and Send shapes, the file is sent to output folder.

Here is the code from Expression shape:
MailVar = null;
MailVar.TestFunc(\”Launch.\”); //MailVar is the variable of my custom class

And here is the code of my method:
public void TestFunc(string launcher)
{
FileStream fout;
fout = new FileStream(@\”C:\\BTalk\\MailTest\\new.txt\”, FileMode.Create);
StreamWriter fstr_out = new StreamWriter(fout);
fstr_out.Write(launcher);
fstr_out.Flush();
fstr_out.Close();
}

Does anyone have an idea why it’s not working ?
It would be very nice, if anyone can help me.

Thanks a lot.
Roman.