FormWindowOpeningMode.LockOwnerWindow

The form is opened on top of the owner.
If the form opens in this mode, the owner window will be locked.
The locked window is determined in the following way:

• If the FormOwner property contains a form and this form is not closed, then this form window is locked;
• If the FormOwner property contains a form element and the form is not closed, then the form window, to which the given element belongs, is locked;
• In other cases (if the FormOwner property is set to Undefined value or the owner form is closed), then the current (on form open) client application window is locked.

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