Bear in mind:
if any ISAPI crashes, the whole IIS will crash and needs a reboot to get out of the hang.

Nobody wants to host ISAPI applications because IIS can hang any-time, and disrupt other websites.

We solved this problem by using our own custom-made memory manager which locks each ISAPI application into a separate memory space and isolate it from the IIS web-server. Since then, NO-ONE complained that their CSharp/VB.NET/or custom website went down.

Nearly everyone who tried to host ISAPI apps got bitten and finally decided not to host ISAPI apps. Otherwise, you would see lots and lots of webhosting companies doing this.