Do yourself a favor, next time you have a build error that says something like: The type or namespace name 'XYZ' could not be found (are you missing a using directive or an assembly reference?). Double click the error (which will highlight the unknown type) then hit Alt+Shift+F10. This will bring up a dropdown that has all of the types that match that class name and hitting enter will automatically add the appropriate using statement. Thank you Visual Studio!