I want to develop an ISAPI filter which shall read the headers of an URL, this shall talk to an ASP .NET application . Can this be achieved in C# , or do I need to develop this in C++ , and create a CLI/C++ DLL so that the ASP .NET application can communicate with the C++ dll .
In .Net you use HTTPModule and HTTPHandlers to accomplish what ISAPI gave you before.
Here is a decent MSDN article: http://msdn.microsoft.com/en-us/library/bb398986.aspx