Pls check the attached Solution. When button launch Popup is clicked, the Pop is displayed. Now using Alt+Tab or from task bar click any other opened application , the pop up does not disappear.
As per provided solution
Try setting the parenntcontrol of the popup to be the form.
popupctrl.ParentControl = this;
Th epop up now though disappeares when task bar other application is clicked but does not disappear when parent form is clicked