How to close a form using X++

There are “only” 5 ways to close a form:
Close - close the form. Similar to the 'X' button.
CloseOK – close the form, and set the OK flag – called by the Commandbutton::Ok
CloseCancel – close the form, and set the Cancel flag – called by the Commandbutton::Cancel
CloseSelectRecord – close the lookup form, and set return record
CloseSelect – close the lookup form, and set return value

The below methods (note their names are in past-tense) are used to determine if or how a form was closed:
Closed – Returns true, if the form is no longer open
ClosedOK – Return true, if the form was closed by the user clicking ‘OK’
ClosedCancel – Returns true, if the form was closed by the user clicking ‘Cancel’

Finally, CanClose() is called before any of the close methods get called. If CanClose() returns false, the form is not allowed to close.