• Check Debug->Options and Settings->General->Enable .NET Framework Source Stepping
• Check Debug->Options and Settings->General->Enable Source Server Support
• add http://referencesource.microsoft.com/symbols to Debug->Options and Settings->Symbols

Once again, I can’t get any of it to work. Access is denied while trying to execute tf.exe view /version:550320 /noprompt “$/DevDiv/D11Rel/FX45RTMRel/ndp/clr/src/BCL/System/MulticastDelegate.cs” /server:http://vstfdevdiv.redmond.corp.microsoft.com:8080/devdiv2 /console > MulticastDelegate.cs.

• http://referencesource.microsoft.com/netframework.aspx – when downloading files from this link, if the file gets downloaded as a .aspx file, change the extension to .msi. See this post for details: http://social.msdn.microsoft.com/Forums/en-US/refsourceserver/thread/f17c11c1-72f6-4529-bafe-5a1d79b72bd7
• Also see, http://referencesource.microsoft.com/troubleshooting.aspx

It also pays to read the setup instructions in the included readme.txt file:

1. Install Reference Source:
   1. Download Microsoft Reference Source Code Center from http://www.referencesource.microsoft.com.
   2. Install Reference Source to any arbitrary location say ‘C:ReferenceSource’.
2. Setup Symbols Path:
   1. Launch Visual Studio 2008/2010.
   2. From the Tools menu, choose Options.
   3. In the Options dialog box, open the Debugging node and select General
      – Uncheck “Enable Just My Code (Managed only)”
      – Check “Enable source server support”
      – Uncheck “Require source files to exactly match the original version”
   4. Select Symbols under Debugging.
      In the Symbol File Locations box, add the downloaded symbols location: C:ReferenceSourceSymbols
      Note: To add the Symbols path Click folder icon.
      Enter in text box under ‘Cache symbols from symbol servers to this directory: C:ReferenceSourceSymbolsCache
3. Debugging your Application
   a) Open your application code solution and build the solution.
   b) Set a break point in the code.
   c) Start debugging (press F5).

Unfortunately, I have tried all of this and can’t get VS Debugger to break on .net source code. I kept investigating this, and finally I was able to break in when I compiled my application as a 32 bit executable. Although Question #5 on the FAQ site says you should be able to debug 64 bit code, if you run into this problem, try compiling as 32 bit (project->Properties->Debug->set Target = x86)