>How to use On key label eg. F1 to run a method in form?
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ON KEY LABEL works outside the context for the Form, so references like "this", "thisform", etc cannot be used in this context. Instead, add code to the KeyPress event of the Form that traps the keystroke(s) of interest, and triggers an appropriate message; this way, the oject context is maintained consistently.

The alternative is to try to add references through the _SCREEN.ActiveForm property reference, which introduces a layer of ambiguity of reference and breaks encapsulation, requiring that all Forms implement the same common set of methods and responds identically to all the same keystrokes. THis is a bad idea.