datagridview导出Excel(以流的方式)

  private   void  ExportToExcel()
        {
            SaveFileDialog saveFileDialog  =   new  SaveFileDialog();
            saveFileDialog.Filter  =   " Execl files (*.xls)|*.xls " ;
            saveFileDialog.FilterIndex  =   0 ;
            saveFileDialog.RestoreDirectory  =   true ;
            saveFileDialog.CreatePrompt  =   true ;
            saveFileDialog.Title  =   " 保存为Excel文件 " ;
            saveFileDialog.ShowDialog();

             if  (saveFileDialog.FileName.IndexOf( " : " )  <   0 )  return ;  // 被点了"取消"

            Stream myStream;
            myStream  =  saveFileDialog.OpenFile();
            StreamWriter sw  =   new  StreamWriter(myStream, System.Text.Encoding.GetEncoding( - 0 ));
             string  columnTitle  =   "" ;
             try
            {
                 // 写入列标题
                 for  ( int  i  =   0 ; i  <  dgvGF_IN_INFO.ColumnCount; i ++ )
                {
                     if  (i  >   0 )
                    {
                        columnTitle  +=   " \t " ;
                    }
                    columnTitle  +=  dgvGF_IN_INFO.Columns[i].HeaderText;
                }
                sw.WriteLine(columnTitle);

                 // 写入列内容
                 for  ( int  j  =   0 ; j  <  dgvGF_IN_INFO.Rows.Count; j ++ )
                {
                     string  columnValue  =   "" ;
                     for  ( int  k  =   0 ; k  <  dgvGF_IN_INFO.Columns.Count; k ++ )
                    {
                         if  (k  >   0 )
                        {
                            columnValue  +=   " \t " ;
                        }
                         if  (dgvGF_IN_INFO.Rows[j].Cells[k].Value  ==   null )
                            columnValue  +=   "" ;
                         else
                            columnValue  +=  dgvGF_IN_INFO.Rows[j].Cells[k].Value.ToString().Trim();
                    }
                    sw.WriteLine(columnValue);
                }
                sw.Close();
                myStream.Close();
            }
             catch  (Exception e)
            {
                MessageBox.Show(e.ToString());
            }
             finally
            {
                sw.Close();
                myStream.Close();
            }
        }