I am making a custom control which is a simple image viewer with an Image and 2 ImageButton controls. I would like these controls' ImageUrl properties to be decided by the user of the control, but as it would not be a good idea to have null values for these properties Ii would like to be able to enforce the assignment of these values at design time. For example Visual Studio prompts you to declare the 'runat="server' attribute for all custom controls.
I really have no idea if this is even possible with custom controls but if anyone could provide a solution to this it would be amazing.
