Test a project
You can verify whether your Microsoft Expression Blend project is working correctly by running it using the Test Project command.
Make sure that the correct project is open in Expression Blend, and then click Test Solution on the Project menu, or simply press F5.
In the Results panel, review the test build process for any errors that may have occurred. If you encounter an error, a build of the project will be unsuccessful, and you will have to repair the error before you can successfully build the project. If the test build is successful, your project will automatically open in an application window.
If the project is a WPF Control Library, the Test Project option is disabled. You can test only a WPF Application. To test a WPF Control Library, add it to a WPF Application. For more information, see "To instantiate the user control in another document" under Try it: Create a WPF user control.