BetaPrivateconstructorReadonlyformThe identifier of the form that caused the visibility error.
This property can be read in early-execution mode.
ReadonlyreasonThe reason the form visibility operation failed.
This property can be read in early-execution mode.
Optionalstack
Thrown when a form visibility operation fails, such as attempting to show a form that is already showing or attempting to close a form that is not currently open.