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 or DropDownList mode. If the control is not in edit or DropDownList mode, this methods does nothing.

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

public override void SetProposedValue( 
   System.object value
)