Can't debug web app

I'm getting this message when I try and attach to process. H开发者_如何学编程ow do I fix this?:

Have you tried "changing its project build configuration to 'Debug' mode"?

The DLL file that you're trying to attach to ("Chatham.Web.DLL") was either built with compiler optimizations enabled or without debug information included. You need to recompile that DLL with optimizations disabled and debug information included. It might also help to "clean" the solution first before you rebuild it.

Are you sure you're in debug mode?

Also in your web.config:

<configuration>
  <compilation debug="true"/>
</configuration>

If you are, and it's another assembly you're hitting, try this link as well.