How can I get smart card Provider ID in windows xp using dot net

Question

I am using c# for developing smart card apps I need to get the smart card provider ID I am trying to use SCardGetProviderId

[DllImport("winscard.dll")]
public static extern SCardErr SCardGetProviderId(IntPtr hContext, string szCard,ref _GUID guid);

[StructLayout(LayoutKind.Sequential)]
public struct _GUID
{
        long Data1;
        short Data2;
        short Data3;
        string Data4;
}

but nothing is being returned in the GUID struct I dont know how to get the smart card name??

How can i get the smart card name ???