Source

Trace to output window without adding code.

Want to trace some run-time data to the output window while debuggingwithout changing and recompiling your code? Use Tracepoints: http://blogs.msdn.com/saraford/archive/2008/06/13/did-you-know-you-can-use-tracepoints-to-log-printf-or-console-writeline-info-without-editing-your-code-237.aspx