Microsoft KB Archive/138063

= Effect of DoEvents in Visual Basic OLE Server DLLs =

Article ID: 138063

Article Last Modified on 12/9/2003

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APPLIES TO


 * Microsoft Visual Basic 4.0 Standard Edition
 * Microsoft Visual Basic 4.0 Professional Edition
 * Microsoft Visual Basic 4.0 Professional Edition
 * Microsoft Visual Basic 4.0 16-bit Enterprise Edition
 * Microsoft Visual Basic 4.0 32-Bit Enterprise Edition

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This article was previously published under Q138063



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.

Additional query words: 4.00 vb4win vb4all

Keywords: KB138063

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