为什么这个Using()给我一个错误？

Question

我正在尝试打开一个(实际上有数百个)excel文件.我打开应用程序但想要在我打开的每个工作簿周围使用Using()功能.为什么会导致错误？

using (Excel.Workbook wbXL = appXL.Workbooks.Open(_sourceFullPath, Type.Missing, Excel.XlFileAccess.xlReadOnly))
{
    //stuff with wbXL
}

使用获取红色下划线并说"'Microsoft.Office.Interop.excel.Workbook':在using语句中使用的类型必须可以隐式转换为'System.IDisposable'.

如何使这项工作？

Answer 1

几乎就是它所说的 - 你只能使用using实现IDisposable的类,因此编译器知道在最终化时调用哪个函数 - yourclass.Dispose().Excel互操作类不实现此功能.

所以你有两个选择:

1. 为实现IDispose的Excel.Workbook编写自己的包装类,并将对象本身暴露给调用方法,或者包装这些方法,例如

   public class DisposableWorkbook : IDisposable
   {
       private Excel.Workbook _workbook = null;
   
       public DisposableWorkbook(Excel.Application appXL, String path,
                                 NotSureOfType otherArgument,
                                 Excel.XlFileAccess access)
       {
           _workbook = appXL.Workbooks.Open(path, otherArgument, access);
       }
   
       public Excel.Workbook Workbook
       {
           get { return _workbook; }
       }
   
       public void Dispose()
       {
           if (workbook != null)
           {
               workbook.Close(Excel.XlSaveAction.xlDoNotSaveChanges,
                              workbookToClose);
               workbook = null;
           }
       }
   }
   
   using (DisposableWorkbook dwbXL = new DisposableWorkbook(appXL,
             _sourceFullPath, Type.Missing, Excel.XlFileAccess.xlReadOnly))
   {
        Excel.Workbook wbXL = dwbXL.Workbook;
        // stuff with wbXL
   }
   

2. 实施using自己,例如

   Excel.Workbook wbXL = null;
   try
   {
       wbxl = appXL.Workbooks.Open(_sourceFullPath, Type.Missing,
                                   Excel.XlFileAccess.xlReadOnly);
       //stuff with wbXL
   }
   finally
   {
       if (wbxl != null) wbxl.Close();
   }