The control is moved to the back of the z-order. If the control is a child of another control, the child control is moved to the back of the z-order. If the control is a top-level control, this method will not work correctly unless the control is active. A top-level control is a control, such as a System.Windows.Forms.Form, that is not a child of another control. An active control is a visible control that has input focus. To use the Control.SendToBack method with an inactive, top-level control, first call the Control.BringToFront method on the control.