public class ImportExportToExcel    {        private string strConn ;                private System.Windows.Forms.OpenFileDialog openFileDlg=new System.Windows.Forms.OpenFileDialog();        private System.Windows.Forms.SaveFileDialog saveFileDlg=new System.Windows.Forms.SaveFileDialog();                      public ImportExportToExcel()        {            //            // TODO: 在此处添加构造函数逻辑            //            this.openFileDlg.DefaultExt = "xls";            this.openFileDlg.Filter = "Excel文件 (*.xls)|*.xls";            this.saveFileDlg.DefaultExt="