public string ExportExcel( DataSet ds,string saveFileName)
        {
            try
            {
                if (ds == null) 
                    return "数据库为空";
         
                bool fileSaved = false;



                Microsoft.Office.Interop.Excel.application xlApp = new Microsoft.Office.Interop.Excel.Application();

                if (xlApp == null)
                {
                    return "无法创建Excel对象，可能您的机子未安装Excel";
                }

                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
                //写入字段
                for (int i = 0; i < ds.Tables[0].Columns.Count; i++)
                {
                    worksheet.Cells[1, i + 1] = ds.Tables[0].Columns[i].ColumnName;
                }
                //写入数值

                for (int r = 0; r < ds.Tables[0].Rows.Count; r++)
                {
                    for (int i = 0; i < ds.Tables[0].Columns.Count; i++)
                    {
                        worksheet.Cells[r + 2, i + 1] = ds.Tables[0].Rows[r][i];
                    }
                    System.Windows.Forms.Application.DoEvents();
                }
                worksheet.Columns.EntireColumn.AutoFit();//列宽自适应。
                if (saveFileName != "")
                {
                    try
                    {
                        workbook.Saved = true;
                        workbook.SaveCopyAs(saveFileName);
                        fileSaved = true;
                    }
                    catch (Exception ex)
                    {
                        fileSaved = false;
                        MessageBox.Show("导出文件时出错,文件可能正被打开！\n" + ex.Message);
                    }
                }
                else
                {
                    fileSaved = false;
                }
                xlApp.Quit();
                GC.Collect();//强行销毁
                if (fileSaved && System.IO.File.Exists(saveFileName)) System.Diagnostics.PRocess.Start(saveFileName); //打开EXCEL
                return "成功保存到Excel";
            }
            catch (Exception ex)
            {
                return ex.ToString();
            }
        }