Problems hosting a WPF control in a windows form

I have a Winform application and want to to use WPF inside this application. I add a WPF user control to my VS project. Then I take a ElementHost control from the toolbox and put it on a form. After that I build the solution.

The problem is now, when I want to embed the WPF control with "Edit Host Content" into the Elemen开发者_StackOverflow中文版tHost controlI get the message "This ElementHost is currently not hosting any editable content....." What's wrong? How can I achieve (in VS) that the ElementHost control knows/references/hosts my WPF control ?