Gets or sets whether the default popup window is modal.
true if the default popup window is modal; otherwise, false.
A modal popup window retains input focus while open. The user cannot switch windows until the popup window is closed.
When enabling the modal mode, make sure that the PopupControlSettings.CloseAction property is set properly. It’s necessary to set the PopupControlSettings.CloseAction property to the CloseAction.CloseButton value, to prevent the popup window from being closed by a click outside the popup, (which is the closing action set by default).