怎么判断Excel单元格格式是哪种

Excel.Application appExcel = new Excel.Application();
appExcel.Application.Workbooks.Open(filePath, miss, miss, miss, miss, miss, miss, miss, miss, miss, miss, miss, miss, miss, miss);
Excel.Workbook wbook = appExcel.Workbooks[1];
Excel.Worksheet sheet = (Excel.Worksheet)wbook.Sheets[1];Excel.Range rag = sheet.get_Range(sheet.Cells[1, 1], sheet.Cells[1, 1]);怎么判断A1单元格格式是数字、日期、文本还是其它。