为什么用OpenFileDialog读取的路径无法写入xml文件

为什么用OpenFileDialog读取的路径无法写入xml文件,请问要怎么写,才能把路径写入INI文件呢?   请高手帮忙,
我写的代码:   先用OpenFileDialog读取的路径,然后显示在TextBox1上,然后保存TextBox1上文件(点击Button2写入ini文件) 不通过OpenFileDialog,直接TextBox1写路径可保存入xml文件,经过读取OpenFileDialog路径就无法写入xml文件了 
OpenFileDialog openFileDialogScl = new OpenFileDialog();
            openFileDialogScl.FileName = "*.mdb";
            openFileDialogScl.Filter = "mdb files (*.mdb)|*.mdb|All files (*.*)|*.*";
            openFileDialogScl.ShowDialog();
            if (openFileDialogScl.ShowDialog() == DialogResult.OK)
            {
                string strPath = System.IO.Path.GetDirectoryName(openFileDialogScl.FileName.ToString()).ToString().Trim();
                textSCLStation.Text = strPath;
            }
其中 stripaddress 就是 textSCLStation
 private void WriteXmlMachine(string fileName,string strIpAddress, string strUser, string strPass, string strHour, string strMin,string strClass,string strDataPass,string strUp,string strRe)
        {
            try
            {
                XmlTextWriter xmlwriter = new XmlTextWriter(fileName,System.Text.Encoding.UTF32);//,System.Text.Encoding.UTF8
                xmlwriter.Formatting = Formatting.Indented;
                xmlwriter.WriteStartElement("Set");
                xmlwriter.WriteComment("设备设置信息");
                xmlwriter.WriteElementString("Station", strIpAddress);
                xmlwriter.WriteElementString("User", strUser);
                xmlwriter.WriteElementString("Pass", strPass);
                xmlwriter.WriteElementString("Hour", strHour);
                xmlwriter.WriteElementString("Min", strMin);
                xmlwriter.WriteElementString("Class", strClass);
                xmlwriter.WriteElementString("DataPass", strDataPass);
                xmlwriter.WriteElementString("Up", strUp);
                xmlwriter.WriteElementString("Re", strRe);
                xmlwriter.WriteEndElement();
                xmlwriter.Close();
            }
            catch (Exception ex)
            {
                return;
            }
        }