Control.SendToBack Method ()
Sends the control to the back of the z-order.
Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
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 Form, that is not a child of another control. An active control is a visible control that has input focus. To use the method with an inactive, top-level control, first call the BringToFront method on the control.
Available since 1.1