Re: SCardGetStatusChange in .NET

From: Pieter Philippaerts (Pieter.nospam_at_mentalis.org)
Date: 11/09/04 

Date: Tue, 9 Nov 2004 16:35:53 +0100

"David" <dflores@rochester.rr.com> wrote
> I am trying to use the Smart Card Win32 API in VB.NET, some of the
> simple functions are easy to declare like SCardEstablishContext and
> SCardListReaders, but I am having trouble declaring SCardGetStatusChange
> function and the structure SCARD_READERSTATE that is passed in. Can anyone
> help with me the correct declaration for both?

Yes, SCardGetStatusChange was the one that gave me the most problems too.
Here's my (working) declaration for it:

[DllImport("winscard.dll", CharSet=CharSet.Auto)]
internal static extern int SCardGetStatusChange(int hContext, int dwTimeout,
[In, Out] SCARD_READERSTATE[] rgReaderStates, int cReaders);

[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Auto)]
internal struct SCARD_READERSTATE {
    [MarshalAs(UnmanagedType.LPTStr)]
    public string szReader;
    public IntPtr pvUserData;
    public int dwCurrentState;
    public int dwEventState;
    public int cbAtr;
    [MarshalAs(UnmanagedType.ByValArray, SizeConst=36)]
    public byte[] rgbAtr;
}

In my case, it was the [In, Out] before the rgReaderStates parameter that
finally solved all my problems.

> p.s. Whatever happened to Win32API.txt? How come it was never updated?

There's a community site at http://www.pinvoke.net/ that's essentially
trying to accomplish the same thing.

Regards,
Pieter Philippaerts

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