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Editorial Team
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Asked: 2026-06-14T15:41:23+00:00

On one computer ‘A’ (win vista 32 bit) if I run my program in

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On one computer 'A' (win vista 32 bit) if I run my program in debug mode all the richtextbox controls throw 'property cannot be set' errors.
I can go on to build the exe (without error ) and the full application OK
But when I then install and run the application on this computer or on computer 'B' (win xp) the same problems occur on both.

However if I run the exact same code in debug mode on computer ‘B‘ there are no errors.
If I build and install the application on computer ‘B‘ it works fine. If I then install this application on computer ‘A‘ it also works fine.
When putting together the application for distribution, both computers use identical copies of richtx32.ocx (it, like the code, is checked out from the same repository).

If I check out previous copies of the code on computer’A‘ (that used to previously behave OK) they also now exhibit the same problems as the latest version of the code.

I don’t have a clue what’s going on, please help!

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1 Answer

  1. Editorial Team

    A bad richtx32.oca file in the system32 directory seems to have been the cause of this.

    Here’s what an .oca file does:

    Some of the properties of the control are provided by the framework
    and some by the control itself. Programmatically, the properties from
    the framework and the control all appear as properties of the control.

    In order for these properties to appear, Visual Basic creates an
    extended type library when the control is loaded into the toolbox.
    Because the process of reading the control’s type library and creating
    the extended type library is time consuming, Visual Basic caches the
    extended type library information into an OCA file.

    If you delete the OCA file for a control Visual Basic recognized,
    Visual Basic will recreate the .OCA file when you load a project
    requiring the control. This recreation process comes with a time
    penalty.

    So it seems that having a bad .oca file in existence can mean that the properties of the control both in the IDE and in the compiled .exe will be affected.
    The solution is to delete the .oca file in the system32 folder and then load the project again.

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