Forms refuse to action on close requests

[Apolon Ivankovic]

Occasionally I get Winform apps which refuse to react to a close request - either via the close cross at the top right of the form or a programmatic Form.Close() method call. The scenario is rare but does happen often enough to be a pain to users. The only recourse for users is then to kill the app with the task manager.

Have the Syncfusion staff experienced this behaviour?
Is it a Winforms bug or does it typically occur as a result of an app programming error?
If it''s the latter, how can you track down what code is causing the problem?

[Administrator]

Off my head, this is caused by bug in Windows Forms. The reason is that somewhere there is a control that got invisible while keeping keyboard focus. Actually Windows Forms tries to Validate control and fails, and then refuses to Close form. Usually, this happens when you have a panel and you show/hide it following application logic. Solution would be focusing another, visible control before hiding panel, for example navigation pane or status bar.

[Administrator]

orangy is right-on, I''ve had to deal with this in the past as well. In addition to the panel situation described, it can also occur if the focus is on a control in a tabpage, then you remove the tabcontrol from the form programmatically.