urlmon.dll FindMimeFromData() works perfectly on 64bit desktop/console but generates errors on ASP.NET

Question

I am creating a library of utilities to be used both in desktop environment in a web environment.

It contains several features that I believe are often repeated in m

Answer 1

If you used the pinvoke signature from the answer your linked, it's defined there like this:

[DllImport(@"urlmon.dll", CharSet = CharSet.Auto)]
private extern static System.UInt32 FindMimeFromData(
    System.UInt32 pBC,
    [MarshalAs(UnmanagedType.LPStr)] System.String pwzUrl,
    [MarshalAs(UnmanagedType.LPArray)] byte[] pBuffer,
    System.UInt32 cbSize,
    [MarshalAs(UnmanagedType.LPStr)] System.String pwzMimeProposed,
    System.UInt32 dwMimeFlags,
    out System.UInt32 ppwzMimeOut,
    System.UInt32 dwReserverd
);

I would rather use the defintion from pinvoke.net:

[DllImport("urlmon.dll", CharSet = CharSet.Unicode, ExactSpelling = true, SetLastError = false)]
static extern int FindMimeFromData(IntPtr pBC,
    [MarshalAs(UnmanagedType.LPWStr)] string pwzUrl,
    [MarshalAs(UnmanagedType.LPArray, ArraySubType=UnmanagedType.I1, SizeParamIndex=3)] 
    byte[] pBuffer,
    int cbSize,
    [MarshalAs(UnmanagedType.LPWStr)] string pwzMimeProposed,
    int dwMimeFlags,
    out IntPtr ppwzMimeOut,
    int dwReserved);

Note the difference in types for ppwzMimeOut and pBC parameter. In the former case, System.UInt32 is not a correct type for a 64-bit pointer under a 64-bit platform. For pBC, this is probably not an issue (as long as it is NULL), but it matters for ppwzMimeOut.

Refer to this implementation which appears to be correct.