请问怎么判断excel里面的表是空的？

Question

怎么判断excel里面的表是空的？Excel.Workbook NewWorkBook;
Excel.Application excel = new Excel.ApplicationClass(); 
excel.Visible=false;
object missing = System.Reflection.Missing.Value ;
NewWorkBook = excel.Workbooks.Open(this.textBox1.Text,missing,missing,missing,missing,missing,missing,missing,missing,missing,missing,missing,missing,missing,missing);
Excel._Worksheet xslWorksheet= (Excel._Worksheet) NewWorkBook.Sheets.get_Item(i);怎么判断xslWorksheet是不是空的？