Flagging Property Changes with the Changed Property

You must set the Property Page's Changed property to True in order to enable the Apply button on the Property Page.

The most appropriate place to set the Changed property is in the corresponding event procedures of the controls you've placed on the Property Page for editing the values of properties.

For example, if a TextBox control on your Property Page represents the value of a property, you would set the Changed property in the TextBox control's Changed event procedure. Again, if an OptionButton control represents a property value, then you'd set the Changed property to True in its Click event procedure.