WPF window host a WPF user control

Hi,

I want to add a WPF user control in a WPF window just as a usual method of adding a user control to window form.

However, after adding a WPF user control in the same project, I can not see this control in the toolbox, although it can be seen when editing a window form. Also, i tried to have those user controls in a seperate project and add reference of the dll. The same thing happened.

So what I should do to add it into a WPF window? Or it is by design that a WPF window can not host any WPF user control?

Anyone has ideas or expierience of this? I'd appreciate your help.

- David