WPF把参数信息写到文件中基本代码

string txt1 = this.HCD_tol.Text;
            try
            {
                double pre_tol = Double.Parse(txt1);
               // StreamWriter sw = new StreamWriter("param.txt");
                sw.WriteLine("ms tol:\t" + pre_tol.ToString("F2"));//F2表示保留小数点后两位小数。
                sw.Flush();
                sw.Close();
            }
            catch (Exception exe)
            {
                MessageBox.Show(exe.ToString());
            }