C/S架构中DataGridView转Excel并实现下载功能

 public void ExportExcel(string fileName, DataGridView myDGV)//将DataGridView转换成excel并提供下载, fileName表示要保存的excel表名称
        {
            string saveFileName = "";
            SaveFileDialog saveDialog = new SaveFileDialog();
            saveDialog.DefaultExt = "xls";
            saveDialog.Filter = "Excel文件|*.xls";
            saveDialog.FileName = fileName;
            saveDialog.ShowDialog();
            saveFileName = saveDialog.FileName;
            if (saveFileName.IndexOf(":") < 0) return; //被点了取消 
            Microsoft.Office.Interop.Excel.Application xlApp = new Microsoft.Office.Interop.Excel.Application();
            if (xlApp == null)
            {
                MessageBox.Show("无法创建Excel对象，可能您的机子未安装Excel");
                return;
            }

            Microsoft.Office.Interop.Excel.Workbooks workbooks = xlApp.Workbooks;
            Microsoft.Office.Interop.Excel.Workbook workbook = workbooks.Add(Microsoft.Office.Interop.Excel.XlWBATemplate.xlWBATWorksheet);
            Microsoft.Office.Interop.Excel.Worksheet worksheet = (Microsoft.Office.Interop.Excel.Worksheet)workbook.Worksheets[1];//取得sheet1 

            //写入标题
            for (int i = 0; i < myDGV.ColumnCount; i++)
            {
                worksheet.Cells[1, i + 1] = myDGV.Columns[i].HeaderText;
            }
            //写入数值
            for (int r = 0; r < myDGV.Rows.Count; r++)
            {
                for (int i = 0; i < myDGV.ColumnCount; i++)