When developing a custom placeholder control an often requested feature is to be able to utilize the standard web author dialogs. E.g. if you need to implement a placeholder control that should allow the user to pick one or many resource gallery items or to add a hyperlink to a posting or channel.
The placeholder controls coming with MCMS allow to do this but if you are developing your own edit control but there is no documented way to utilize these controls in a custom placeholder control.
The following article discusses how to achieve this: