Unable to attach to application 'iisexpress.exe'

Question

I am trying to run my web application and I get this error

Unable to attach to application 'iisexpress.exe' (PID 708) using '<my machine name>'.  The version of clr.dll in the target does not match the one mscordacwks.dll was built for.  Do you want to continue anyway?

This was working yesterday. I have a feeling something has gor corrupted somewhere.

Any idea what is going on here?

Solution

I just had the same problem and I stumbled upon your question. But then I also stumbled upon these:

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

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

One of 3 things seemed to work for everyone.

1. Restart Visual Studio.
2. If you recently had a windows update but a restart is still pending, then restart your computer.
3. Install this service pack http://www.microsoft.com/en-us/download/details.aspx?id=23691

Comments

[parliament]

For me it was definitely the windows update. After reading this it just came to my attention that I've been postponing that restart :)

[MikeTeeVee]

I noticed earlier my CPU spike and that my work forced an update to my machine. Then I started seeing this error. Restarting Visual Studio fixed it for me. Still gonna reboot now cause, why not.