Once a selection has been made (programatically using Select or by the user using MouseInteract) then the user cannot make a new selection (though they can still move or resize the selection if Sizeable or Moveable is specified)

public bool DisableNewSelection { get; set; }

Public Property DisableNewSelection As Boolean
	Get
	Set

public:
property bool DisableNewSelection {
	bool get ();
	void set (bool value);
}