How to convert ISAPI related methods and structures to C# - pinvoke

Question

I have an ISAPI filter written for IIS6. I now need to write a wrapper for IIS7 to wrap the IIS6 filter. I plan to write HTTP module in C# and Pinvoke the unmanaged dll methods.
I need C# representation of the following code,
DWORD WINAPI HttpFilterProc(
PHTTP_FILTER_CONTEXT pfc,
DWORD notificationType,
LPVOID pvNotification
);
typedef struct _HTTP_FILTER_CONTEXT HTTP_FILTER_CONTEXT {
DWORD cbSize;
DWORD Revision;
PVOID ServerContext;
DWORD ulReserved;
BOOL fIsSecurePort;
PVOID pFilterContext;
BOOL GetServerVariable;
BOOL AddResponseHeaders;
BOOL WriteClient;
VOID * AllocMem;
BOOL ServerSupportFunction;
} HTTP_FILTER_CONTEXT, * PHTTP_FILTER_CONTEXT;
I tried using PInvoke Assistant from codeplex but i am not able to make it work.
Has anyone done anything like this before?
Can anyone provide a solution to the above?
Correction: Correct structure added

Answer 1

Building on the code in your answer you need to use the following:
[DllImport(#"XyzISAPI.dll")]
public static extern uint HttpFilterProc(
ref HttpFilterContext pfc,
uint notificationType,
IntPtr pvNotification
);
The native code is passed a pointer to the context struct and passing the struct by ref is the easy way to match that. The final parameter is LPVOID, which is void* and that is plain IntPtr in managed code.
As for HTTP_FILTER_ACCESS_DENIED, define it like this:
[StructLayout(LayoutKind.Sequential)]
public struct HttpFilterAccessDenied
{
IntPtr URL;
IntPtr PhysicalPath;
uint Reason;
}
You can then obtain one of those like this:
HttpFilterAccessDenied hfad = (HttpFilterAccessDenied)Marshal.PtrToStructure(
pvNotification, typeof(HttpFilterAccessDenied));
And then you can get hold of the string values from the struct with Marshal.PtrToStringUni or Marshal.PtrToStringAnsi.