MFC ActiveX Controls: Returning Error Codes From a Method
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This article describes how to return error codes from an ActiveX control method.
To indicate that an error has occurred within a method, you should use the COleControl::ThrowError member function, which takes an SCODE (status code) as a parameter. You can use a predefined SCODE or define one of your own.
Note
ThrowError is meant to be used only as a means of returning an error from within a property's Get or Set function or an automation Method. These are the only times that the appropriate exception handler will be present on the stack.
Helper functions exist for the most common predefined SCODEs, such as COleControl::SetNotSupported, COleControl::GetNotSupported, and COleControl::SetNotPermitted.
For a list of predefined SCODEs and instructions on defining custom SCODEs, see the section Handling Errors in Your ActiveX Control in ActiveX Controls: Advanced Topics.
For more information on reporting exceptions in other areas of your code, see COleControl::FireError and the section Handling Errors in Your ActiveX Control in ActiveX Controls: Advanced Topics.