title: "PDB does not match image" error in C# VS2010 project
body: <p>I've been using a library in my code base for a while now, and I wanted to debug right into the library level.  To do that, I downloaded the source code and included the project as an existing project into my C# solution.  I then had my other projects reference that project instead of the downloaded .DLL.</p>
  
  <p>Once the project was referenced instead of the DLL, I ran my solution through the debugger and tried to step into a function call that would have called into the external project, but it stepped right over it.  While debugging, I opened up the "Modules" window and saw that the DLL's Symbol Status read "PDB does not match image", which is the likely cause of not being able to debug this project.</p>
  
  <p>My question is simple, why does the PDB not match the image if my project is directly referencing the .csproj file as a reference?  There should never be any ambiguity as to what version to run.</p>