Effect of DoEvents in Visual Basic OLE Server DLLs

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

SUMMARY

A DoEvents statement inside a inproc OLE server might cause reentrancy problems.

MORE INFORMATION

If you make a call to an inproc OLE server by say, clicking a command button on a form on some client and that call uses DoEvents, Visual Basic will yield to process other pending messages. If now due to some user action another inproc call or the same one is made to the same DLL server, there is nothing to prevent the DLL code from being re-entered. This might cause unforeseen problems depending on the situation, so this scenario is best avoided. Another problem with DoEvents in a DLL is that you are processing messages for the host (.exe file) in your message loop. The host may have special code in its message loop to handle some messages, and problems may occur when this code is not executed.