Control.Invalidate Method (Region)
Invalidates the specified region of the control (adds it to the control's update region, which is the area that will be repainted at the next paint operation), and causes a paint message to be sent to the control.
Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
Calling the Update method after calling the method. When this method is called with no parameters, the entire client area is added to the update region.method does not force a synchronous paint; to force a synchronous paint, call the
Available since 1.1