The version of clr.dll in the target does not match the one mscordacwks.dll was built for

Question

I am working in an ASP.NET MVC 3 application using the .NET framework 4.0. When I go to debug my application, i get the message:

\"Unable to attach to application \'webd

Answer 1

I have finally solved this!

It seemed to have happened after I updated my Windows 7. One of my files must have been out of date.

The fix: Install VS 2010 Service Pack 1: http://www.microsoft.com/downloads/en/details.aspx?FamilyID=75568aa6-8107-475d-948a-ef22627e57a5

Worked correctly right after I installed. Hitting breakpoints and everything!

Answer 2

Just had this issue and simply restarting Visual Studio fixed it for me.