This method works exactly as setting the Value property, except that it does not change the internal variable storing the value before editing, so the user can press Esc and restore the previous value. This method works only in edit mode. If the control is not in edit mode, this methods does nothing.

'宣言
 
Public Overridable Sub SetProposedValue( _
   ByVal value As System.Object _
) 

public virtual void SetProposedValue( 
   System.object value
)