Do not call the protected AssignTo method. Instead, applications call the Assign method to copy the properties of another object. If the object's Assign method does not include the ability to copy from the source object, the Assign method calls the source object's protected AssignTo method, to copy the source objects properties to the object specified by the Dest parameter. This allows objects to expand the abilities of another object's Assign method to copy from additional sources. 

The AssignTo method implemented in TWinControl copies the Caption, Enabled, Hint, Visible, and HelpContext properties and the OnClick event handler to a TCustomAction object. 

Assign 

TCustomAction 

Caption 

Enabled 

Hint 

Visible 

HelpContext 

OnClick