DataTable 导出到TXT

   public static string  cExportTXT(DataView dv)
        {
            try
            {
                SaveFileDialog saveFileDialog1 = new SaveFileDialog();


                saveFileDialog1.Filter = "txt(*.txt)|*.txt";
                saveFileDialog1.FilterIndex = 0;
                saveFileDialog1.RestoreDirectory = true;
                saveFileDialog1.CreatePrompt = true;
                saveFileDialog1.Title = "导出txt文件到 ";

                DateTime now = DateTime.Now;
              //  saveFileDialog1.FileName = now.Second.ToString().PadLeft(2, '0');
                saveFileDialog1.FileName = DateTime.Now.ToString("yyyyMMddHHmmss") + "_AA";

                //now.Year.ToString().PadLeft(2)+now.Month.ToString().PadLeft(2, '0 ') +now.Day.ToString().PadLeft(2, '0 ')+ "_ " +now.Hour.ToString().PadLeft(2, '0 ') +now.Minute.ToString().PadLeft(2, '0 ') +
                saveFileDialog1.ShowDialog();
                if (saveFileDialog1.FileName.Length==2)
                {
                    return "";
                }
                Stream myStream;
                myStream = saveFileDialog1.OpenFile();
          
                //StreamWriter   sw=new   StreamWriter(myStream,System.Text.Encoding.GetEncoding( "gb2312 "));
                //StreamWriter sw = new StreamWriter(myStream, System.Text.Encoding.GetEncoding("gb2312"));
                StreamWriter sw = new StreamWriter(myStream, System.Text.Encoding.GetEncoding("utf-8"));
                 
                String str = "";
                //写标题
                for (int i = 0; i < dv.Table.Columns.Count; i++)
                {
                    if (i > 0)
                    {
                        str += "\t";
                    }
                    str += dv.Table.Columns[i].ColumnName;
                }
                sw.WriteLine(str);
                //写内容
                for (int rowNo = 0; rowNo < dv.Count; rowNo++)
                {
                    String tempstr = "";
                    for (int columnNo = 0; columnNo < dv.Table.Columns.Count; columnNo++)
                    {
                        if (columnNo > 0)
                        {
                            tempstr += "\t";
                        }
                        //tempstr+=dg.Rows[rowNo,columnNo].ToString();
                        tempstr += dv.Table.Rows[rowNo][columnNo].ToString();
                    }
                    sw.WriteLine(tempstr);
                }
                sw.Close();
                myStream.Close();

                MessageBox.Show("Export successful！");
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString());
                return ex.ToString();
            }
            return "";
        }