Ode to .NET:

snippets.cpp

/* This: */
if (((System::Collections::IList ^)filterData->OpenSubKey("day_filter")->GetSubKeyNames())->Contains("days") == true) {
	...
}


/* Or this: */
using System::Collections;

...

array<System::String ^> subKeys = filterData->OpenSubKey("day_filter")->GetSubKeyNames();
if ((IList ^)subKeys)->Contains->("days")) {
	...
}