System.Windows.Forms.SaveFileDialog.OpenFile C# (CSharp) Method

		public Stream OpenFile ()
		{
			if (FileName == null)
				throw new ArgumentNullException ("OpenFile", "FileName is null");
			
			Stream retValue;
			
			try {
				retValue = new FileStream (FileName, FileMode.Create, FileAccess.ReadWrite);
			} catch (Exception) {
				retValue = null;
			}
			
			return retValue;
		}
		#endregion	// Public Instance Methods

 public void ExportToTxt(DataView dv)
 {
     string fn = "bf" + Common.ChineseToSpell.GetChineseSpell(cmbLb.SelectedValue.ToString()).ToLower();//此处把值转换为拼音
     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 = fn;
     saveFileDialog1.ShowDialog();
     Stream myStream;
     myStream = saveFileDialog1.OpenFile();
     StreamWriter sw = new StreamWriter(myStream, System.Text.Encoding.GetEncoding("gb2312"));
     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 += dv.Table.Rows[rowNo][columnNo].ToString();
         }
         sw.WriteLine(tempstr);
     }
     sw.Close();
     myStream.Close();
 }