Excel COM对象强制转换错误

我正在努力避免在代码中使用"双点"表示法（请参阅如何正确清理Excel互操作对象？）。然而，当我试图更改以下代码时，我遇到了一个错误

Excel.Workbook oWB;
...
oWB.Sheets[oWB.Sheets.Count].Delete();
oWB.Sheets[oWB.Sheets.Count].Delete();
oWB.Sheets[oWB.Sheets.Count].Delete();

到这个

Excel.Sheets oS;
oS = oWB.Sheets;
//error occurs in the following line
oS = oWB.Sheets[oS.Count];
oS.Delete();
oS.Delete();
os.Delete();

错误为'Unable to cast COM object of type 'System.__ComObject' to interface type 'Microsoft.Office.Interop.Excel.Sheets'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{000208D7-0000-0000-C000-000000000046}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).'

感谢您的帮助。