Codes not generate the file properly

Hi,
I don't know why these codes below are not creating any .xml file when I run the project.
                    string FILENAME = Server.MapPath("~") + "..\\..\\xml\\common.xml";
                    ?XmlTextWriter textwrt = new XmlTextWriter(FILENAME, null);
                    textwrt.WriteStartDocument();
                    textwrt.WriteStartElement("Common");
                    textwrt.WriteAttributeString("field1", tb_fld1.Text);
                    textwrt.WriteAttributeString("field2", tb_fld2.Text);
                    textwrt.WriteEndElement();
                    textwrt.Close();

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Many Thanks & Best Regards, Hua Min