title: Create multi-projects with one solution
body: <p>I am a pretty know in WPF, I created three projects in one Solution, Example Project1, Project2 and Project3.</p>
  
  <p>When I build solution, only Project1 that has it's own dll(Project1.dll), In Project3 need to use Project2.dll, but my Project2 and Project3 don't have it's own dll file, but in WinForm is okay.</p>
  
  <p>My question is, why Project2 and Project3 don't have dll file like a Project1?</p>
  
  <p>Thank in advance for any answer!</p>