Unable to start program 'http://localhost/Default.aspx'. VS2010

Question

I cannot start my website from Visual Studio 2010 anymore.

For a few days I cannot start my project in a web browser using F5. When I open my web application directly by

Answer 1

Does it work if you start it with [CTRL]+[F5] which runs without the debugger?

If so, then you have an issue with the debugger auto-attaching to the web server. I would check that debugging is enabled for your web project - a warning that usually crops up automatically from VS when it detects that a project is not built in Debug mode.

This is not as simple as switching the project configuration over to Release, because the DLL that the debugger is moaning about is one of the dynamically generated ones originated by Asp.Net itself.

Typically you should have, in your web.config:

(Along with any other stuff in and nodes).

There's also the possibility that Asp.Net debugging is not, for some reason, enabled.

Check out this msdn article on debugging asp.net applications in VS2010 for more information.

Note that if this is VS010 express, then you won't be able to debug - as confirmed by the aforementioned link; but since you way it used to work then I guess that's not your problem.

Update

Since that hasn't worked - you can try emptying the Temporary ASP.Net files folder. Easiest first is to do an iisreset. Then navigate to C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files and delete everything in it. I've had issues in the past where the Asp.Net binaries don't get refreshed and so when I'm debugging it moans that the files are out of date.