使用 Excel.Workbook.Sheets 集合，更容易访问

Instead of the using Excel.Workbook.Sheets collection, it's easier to access the Excel.Workbook.Worksheets collection, that way you can utilize early binding.

在您的情况下，可能看起来像以下内容：

In your case, it could look something like the following:

Excel.Application excelApp = new Excel.Application();
excelApp.Visible = true;

Excel.Workbook workbook = excelApp.Workbooks.Open("C:\MyWorkbook.xls",
    Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, 
    Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, 
    Type.Missing, Type.Missing, Type.Missing, Type.Missing);

// The key line:
Excel.Worksheet worksheet = (Excel.Worksheet)workbook.Worksheets["SubSignOff"];

希望这有帮助...