Untrapped Errors in VB OLE DLL Can Unload the Whole Process

• Professional and Enterprise Editions of Microsoft Visual Basic, 16-bit and 32-bit, for Windows, version 4.0

SUMMARY

Untrapped errors in any events (like Initialize and Terminate) in an in-process OLE DLL server created in Visual Basic will cause it to terminate the whole process.

MORE INFORMATION

If you don't have an On Error Goto statement inside an Event procedure in an in-process OLE DLL server created in Visual Basic and an error occurs inside the event procedure, Visual Basic will call the ExitProcess Windows API to terminate the process that loaded the DLL. This will happen regardless of the Error trapping setting on the Advanced tab when you click Options on the Tools menu and regardless of whether the client is running in the Visual Basic IDE or as a separate EXE.

Errors in event handlers of forms or controls created by the OLE DLL also have the same problem. For example, if the OLE DLL brings up a modal form and the user clicks on the form, an untrapped error in the Form_click event will cause the entire process to terminate.

However, this does not apply to errors that occur in property procedures or methods of objects in the DLL. If these errors are not trapped in the DLL they will be sent on to the client application that called the procedure.