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>Hi Sergey
>
>Didn't know about your book!

I don't have one. It's just an expression. :)

>
>To continue this discussion and to gather some more knowledge from you...
>
>This C0..05 got me working on the form again and again. I have, as you already know, defined a property THISFORM.oSetFocusPage. This property I have defined visually, so when you suggested about dangeling reference, I tried to recreate the C0.05 and was always succesful, even though I had set the property to null in the thisform.destroy()
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>I changed the clicking and closing order, more on that later, of the form and the C.5 went away, I removed the setting to null in destroy() and still the C.5 didn't reapprear.
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>Q1. Does this mean that visually created properties which are object references or object themselves are nicely cleaned up by VFP?
>Q2. Manually created variables should be the programmers responsibility to null and release as the VFP wouldn't know about it?
>
>
>Assuming it is my fault first and not the frameworks. I tried to clean up as many local references to objects (the calls to these functions were commented so basically non-executing codes) in the i-Layer of the form of which the above form is subclassed.
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>Surprisingly of all the forms subclassed and instatiated using this same i-Layer form class, were working very well for a given order of clicking, only this one form misbehaves.
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>The order of clicking is... Instantiate the form using the toolbar of the app. Click on Page2 containig a grid. Click the close button. Bang C.5 for only one form of all the subclassed forms.
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>Further study showed that of all these form classes the naughty one and another form have this grid on page2 does no have the columns populated for the fields to show. All other forms have the grid with the columns specified using a builder.
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>Q3. Then why would one form C.5 and the other one does not?
>Q4. This naughty form will also generate a This program has performed an illegal operation if I try to close the designer window when the page containing the grid is at the front

Are you sure that your form isn't corrupted in some way?