public void saveAsExcel(string path, DataTable tbdt)
        {
            object objMissing = System.Reflection.Missing.Value;
            Microsoft.Office.Interop.Excel.Application app = new Microsoft.Office.Interop.Excel.Application();
            app.Visible = false;
            Microsoft.Office.Interop.Excel.Workbook workBook = app.Workbooks.Add(objMissing);
            Microsoft.Office.Interop.Excel.Worksheet workSheet = (Microsoft.Office.Interop.Excel.Worksheet)workBook.Worksheets[1];
            for (int i = 0; i < tbdt.Columns.Count; i++)
            {
                Microsoft.Office.Interop.Excel.Range head = (Microsoft.Office.Interop.Excel.Range)workSheet.Cells[3, i + 1];
                head.Value = tbdt.Columns[i].ColumnName;
                head = null;
            }
            Microsoft.Office.Interop.Excel.Range range = workSheet.get_Range("A4", objMissing);
            int rows = tbdt.Rows.Count, cols = tbdt.Columns.Count;
            Microsoft.Office.Interop.Excel.Range ranges = range.get_Resize(rows, cols);
            object[,] datas = new object[rows, cols];
            for (int i = 0; i < rows; i++)
            {
                for (int j = 0; j < cols; j++)
                {
                    datas[i, j] = tbdt.Rows[i][j].ToString();
                }
            }
            ranges.Value = datas;
           
            workBook.SaveAs(path, objMissing, objMissing, objMissing, objMissing, objMissing, Microsoft.Office.Interop.Excel.XlSaveAsAccessMode.xlNoChange, objMissing,
                objMissing, objMissing, objMissing);
            workBook.Close(false, objMissing, objMissing);
            app.Quit();
            range = null;
            ranges = null;
            workBook = null;
            workSheet = null;
            app = null;
        }