don't worry about this. "Pages" is generated dynamically. We're not sure why yet, but occasionally Visual Studio will "forget" this and will list "Pages" as missing. In any case, this is not a problem and it won't interfere with your work.
Try replacing the two instances of "Pages" with "TestProject.Pages" - this way the errors might not appear.
Let me know whether this works!
All the best,
the Telerik team