先判断f盘下面是否存在该文本文件，如果不存在，则新建文件，然后往该文本文件写入字符串：strSql

                string path = @"F:\20140303.txt";

                if (false == System.IO.File.Exists(path))
                {
                    System.IO.StreamWriter SW;
                    SW = System.IO.File.CreateText(path);
                    SW.Close();
                }
                if (strSql != "")
                {
                    System.IO.StreamWriter SW = new System.IO.StreamWriter(path, false);
                    SW.Write(strSql);
                    SW.Close();
                }