Hiya Colin

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>1. In VFP 5 I created my own class library which was a straight subclass (no changes) of VFP's base classes (i.e. TextBox, ComboBox, etc.) I now have VFP 5 uninstalled and VFP 6 installed. Will myTextBox class reference VFP 6's TextBox as base class?
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Only if you recompile the classlib in VFP6.

>2. Should I create my own class library of subclassed VFP6 Foundation Classes? Also, what foundation classes, if any, did you find immediately usefull?
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Create your own class libs of the FFC if you want to change them. I found the Dialog FFC classes (splash, about, etc screens) immediately useful.