Winforms add Form to Component via Interface

Question

I have DevExpress XtraForm, which implements a self written Interface. Then i have component, which has an Property from the Type of the Interface. So i thought if i pull the component to the Form, i can set the Form as value for the component Property. But this doesnt work. The Designer doesn't show my Form in the Menu. If i change the PropertyType of my component to XtraForm it works as expected.

1. Winform implements ITest
2. Component got Property from Type ITest
3. Winform add Component
4. In Designer i can see the Property of the component but its not possible to set. Dropdown-Dialog is empty.

Someone can help me?