Exceptions: OLE Exceptions

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The techniques and facilities for handling exceptions in OLE are the same as those for handling other exceptions. For further information on exception handling, see the article Exception Handling Topics.

All exception objects are derived from the abstract base class CException. MFC provides two classes for handling OLE exceptions:

• COleException   For handling general OLE exceptions.
  
  
• COleDispatchException   For generating and handling OLE dispatch (automation) exceptions.

The difference between these two classes is the amount of information they provide and where they are used. COleException has a public data member that contains the OLE status code for the exception. COleDispatchException supplies more information, including the following:

• An application-specific error code
  
  
• An error description, such as “Disk full”
  
  
• A Help context that your application can use to provide additional information for the user
  
  
• The name of your application’s Help file
  
  
• The name of the application that generated the exception

COleDispatchException provides more information so that it can be used with products like Microsoft Visual Basic. The verbal error description can be used in a message box or other notification; the Help information can be used to help the user respond to the conditions that caused the exception.

Two global functions correspond to the two OLE exception classes: AfxThrowOleException and AfxThrowOleDispatchException. Use them to throw general OLE exceptions and OLE dispatch exceptions, respectively.