c# 从excel中抽取信息，遇到“未将对象引用到实例”

 Excel.Workbook xBook = excelApp.Workbooks._Open(openStr, obj, obj, obj, obj, obj, obj, obj, obj, obj, obj, obj, obj);
  Excel.Worksheet xSheet = (Excel.Worksheet)xBook.Sheets[1]; 

开始为，报上述问题                   

Excel.Range rng16 = (Excel.Range)xSheet.Cells[1, 6];
string WorkIdConent = rng16.Value2.ToString().Trim();

解决为，

Excel.Range rngBasePriceStuff = (Excel.Range)xSheet.Cells[i+2, 6];

string BasePriceStuff = Convert.ToString(rngBasePriceStuff.Value2);

BasePriceStuff  可以为空。