Simply end all Webdev.WebServer.exe processes – did the trick for me.
Occasionally this ‘unable to launch because port is in use’ error happens when one of the visual studio processes (webdev.webserver.exe) is still running and locked. The webdev.webserver process(s) should end when you close your browser or app but if they dont (for instance my Visual Studio crashed but if left the webserver still running) then this could lock the port and this will prevent visual studio from launching your project. When you try to F5 your app (launch your application from visual studio) then it conflicts with the current port in use and the above ‘because port XYZ is in use‘ error is displayed.
So to fix it: in the status bar (next to your windows clock) right-click and ‘Stop’ all the ASP.net development server icons. You can also open task manager and kill all the webdev.webserver.exe processes.
