ERROR_INVALID_HANDLE in .NET app with winscard.dll

Question

I'm creating a .NET Windows service to communicate with a smart card reader. The maincomponent is a Windows DLL called winscard.dll which I'm using with DLLImport attribute in the .NET code. Everything works fine on Windows XP 32 bit, but when i running it on Windows 7 x64 i recive 0x6 ERROR_INVALID_HANDLE result when calling SCardTransmit. The application (the service as command line app) can connect to the card reader but cannot read anything from the card.

Any idea?

Have you tried build your .NET application as a 32 BIT program rather than anycpu? — Mike Miller
If i build it as 32 bit app, then: Unhandled Exception: System.AccessViolationException: Attempted to read or write protected memory. This is often an indication that other memory is corrupt. at Microsoft.Win32.Win32Native.CoTaskMemFree(IntPtr ptr) at SmartCard.SmartCardBase.SCardListReaderGroups(Int32 hContext, String& cGro ups, Int32& nStringSize) at SmartCard.SmartCardBase.InitializeCardReader() in C:\Data\K7 Intranet\Smar tCard\SmartCardBase.cs:line 152 at SmartCard.Program.Main(String[] args) in C:\Data\K7 Intranet\SmartCard\Pro gram.cs:line 14 — Peter Kiss
It seems you aren't the only one (groupsrv.com/dotnet/about280604.html). It doesn't much more information then you already have though. — Mike Miller
The solution: use IntPtr instead of int (any type) and implement all winscard.dll method good, help: pinvoke.net — Peter Kiss

Artem Artem · Accepted Answer · 2012-11-29T03:26:01

You have problems with SCardEstablishContext it will return 0 but handle also 0. Use IntPtr instead of Integer:

Public Declare Function SCardEstablishContext Lib "Winscard.dll" (ByVal dwScope As Integer, _
                                                                      ByVal pvReserved1 As Integer, _
                                                                      ByVal pvReserved2 As Integer, _
                                                                      ByRef phContext As IntPtr) As Integer

phContext will be store valid value in Windows x64 (Windows 8 x64 and Windows 2008 via RDP tested). Also replace other "Integer" to "IntPtr" when it used as handle.

Public Declare Function SCardConnect Lib "Winscard.dll" Alias "SCardConnectA" (ByVal hContext As IntPtr, _
                                                                                   ByVal szReaderName As String, _
                                                                                   ByVal dwShareMode As Integer, _
                                                                                   ByVal dwPrefProtocol As Integer, _
                                                                                   ByRef hCard As IntPtr, _
                                                                                   ByRef ActiveProtocol As IntPtr) As Integer

ERROR_INVALID_HANDLE in .NET app with winscard.dll

1 Answers