ControlDesigner.RegisterClone Method (Object, Object)
Registers internal data in a cloned control.
Assembly: System.Design (in System.Design.dll)
Whenever an item is cloned, there might be some internal data structures, such as meta: attributes, that should be included in the cloned control by the control designer. A page developer might add meta: attributes to the markup of a control and there is no way, nor is there a reason, for the control to distinguish what those tags might be. Therefore, if your control designer provides a way to edit complex properties or formats before applying changes to a page, you would create a clone of the control, pass both the original control and the clone to thismethod, and then, when the changes are persisted to the tag, all meta: attributes are also persisted.
Available since 2.0