I'm maintainning a Windows Search property handler project, it is loaded by SearchFilterHost.exe. I don’t know when SearchFilterHost.exe will be launched, don’t know the command line arguments usage, and I find SearchFilterHost.exe will exit one or two minutes after started, so it’s difficult to use the debugger to attach the process then debug the DLL it loaded.
How to debug a Windows Search property handler?
Debugging Protocol Handlers in MSDN talks about how to do this. It involves adding registry entries to make SearchIndexer and SearchFilterHost a little more friendly to debug. You probably will need to take ownership of the registry branch(es) to be able to change the values. Just doing the first set may be enough for you to be able to directly attach to SearchFilterHost.
Once you have things set up, restart the WSearch service, tweak your searched file, and things should happen.
Also, here's an old thread of others' experiences. Among other things, it talks about using the MSDN tool IFiltTst in your project's debug settings.
Both methods require your DLL to be registered so it will be found by Search.