Question

I mean, I’ve got a checkbox, and when it click on it.. I need to run a function to verify if can change IsChecked value or not.

It seems like a validation.

Answer 1

You can use the Checked (UnChecked/CheckedChanged) event(s) of the checkbox (depending on if its a WPF or a WinForms application):

CheckBox cb;
...
//WPF:
cb.Checked += (sender,e) => { if (!..check if new state is valid..) cb.Checked = !cb.Checked) };
cb.UnChecked += ...
//WinForms:
cb.CheckedChanged += ...

If the new checked state is not valid, it (un)checks the checkbox again and puts it in a valid state.

Another (and better) approach would be to disable the checkbox if a certain condition is not met (like a state of another control). It is confusing for the user if he or she checks a box and it’s state is not changing without any feedback.

See MSDN for WPF / MSDN for WinForms for further informations.