通过文件流将DataGridView中的数据导出

/// <summary>
        /// 将DataGridView中的数据导出到Excel
        /// </summary>
        /// <param name="dgvMain"></param>
        private void DataGridViewToExcel(DataGridView dgvMain) {
            //声明保存对话框
            SaveFileDialog saveFileDialog = new SaveFileDialog();
            //文件后缀列表
            saveFileDialog.Filter = "文本文件(*.txt)|*.txt";
            //设置过滤器索引
            saveFileDialog.FilterIndex = 0;
            //关闭对话框之后，下次打开恢复原来的目录
            saveFileDialog.RestoreDirectory = true;
            //设置如果文件不存在、是否提示用户创建该文件
            saveFileDialog.CreatePrompt = true;
            //设置对话框标题
            saveFileDialog.Title = "保存为Excel文件";
            //接受客户端响应、当用户单击保存后执行
            if (saveFileDialog.ShowDialog() == System.Windows.Forms.DialogResult.OK) {
                //创建文件流
                Stream stream = saveFileDialog.OpenFile();
                //创建写入器
                StreamWriter streamWrite = new StreamWriter(stream,System.Text.Encoding.GetEncoding(-0));
           
                string columnTitle = "";  //列标题
                try
                {
                    //写入列标题
                    for (int i = 0; i < dgvMain.ColumnCount; i++)
                    {
                        if (i > 1)
                        {
                            columnTitle += "\t\t";
                        }
                        columnTitle += dgvMain.Columns[i].HeaderText;
                    }
                    //将标题写入文件流
                    streamWrite.WriteLine(columnTitle);

                    //写入列内容
                    for (int i = 0; i < dgvMain.Rows.Count; i++)
                    {
                        string columnValue = "";
                        for (int j = 0; j < dgvMain.Columns.Count; j++)
                        {
                            if (j > 1)
                            {
                                columnValue += "\t\t";
                            }

                            if (dgvMain.Rows[i].Cells[j].Value == null)
                                columnValue += "";
                            else                
                                columnValue += dgvMain.Rows[i].Cells[j].Value.ToString().Trim();
                        }
                        //将行数据写入文件流
                        streamWrite.WriteLine(columnValue);
                    }
                }
                catch (Exception err)
                {
                    MessageBox.Show(err.Message);
                }
                finally {
                    //关闭文件流
                    streamWrite.Close();
                    stream.Close();
                }
            }

        }