How do .NET profilers work?

Question

I am thinking about adding a diagnostics mode build into an app I am writing to count method usage and execution time, similar to what many code profilers like dotTrace do.

I'm having some trouble finding resources through google on how to accomplish this though; obviously it is possible, but can anyone point me to some resources on how I can implement something like method call counts in .NET?

Answer 1

The Code Project article Creating a Custom .NET Profiler describes the process of creating a profiler using the CLR profiler hooks.

This involves creating a COM object that implements the ICorProfilerCallback2 interface and then using environment variables to indicate to the CLR that we wish to profile by using this class:

When the CLR begins a process, it looks for two environment variables:

• COR_ENABLE_PROFILING: This environment variable is set to either 1 or 0. 1 indicates that the CLR should use a profiler. 0 (or the non-existence of this environment variable) indicates that it should not use a profiler.
• COR_PROFILER: Now that we've told the CLR that we want to profile, we have to tell it which profiler to use. Because profilers are implemented as COM objects, this environment variable will be set to the GUID of the coclass that implements the ICorProfilerCallback2 interface.

Answer 2

Perhaps I am being too simple here, but my solution to this would be logging. Using entlib or log4net and log debug level messages. Then you can just write a little script/program to analyse the log file and give you the method count. There might even be other log diagnostic tools.

Unless you need rich visualization or real time complex relationship mapping etc. Would you need a profiler? For method count and execution time, wouldn't a log file suffice? Once you are in production or don't care about instrumentation you turn your logging level up and forget about those debug messages.