datatype for 64bit vb.net project

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I have a old vb6 project.Now I migrating it in vb.net on vs2008 and the solution plateform now I have to use 64bit.In the old code the variable hContext was declared as Integer.

VB

Dim hContext As Integer

And used as

VB

Dim rc As Integer
dwScope = SCARD_SCOPE_USER
rc = SCardEstablishContext(dwScope, 0, 0, hContext)

When I debug the code the hContext create problem.
This is due to it define as a Integer(32bit).
Now the problem is "What datatype should I use for hContext".I have also used different datatype like Long,ULong.

Posted 7-Nov-11 1:35am

vikky08

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2 solutions

Solution 1

From the Microsoft API we see the following :

C++

LONG WINAPI SCardEstablishContext(
  __in   DWORD dwScope,
  __in   LPCVOID pvReserved1,
  __in   LPCVOID pvReserved2,
  __out  LPSCARDCONTEXT phContext
);

As you can see the return type is a long which is 8 bytes on 32bit and 64bit systems.

Posted 7-Nov-11 3:14am

Mehdi Gholam

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Sergey Alexandrovich Kryukov 7-Nov-11 16:46pm

Yes, but the question is about hContext. You should take into account that 3 parameters are pointers. Please see my solution.
--SA

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Sergey Alexandrovich Kryukov · Accepted Answer · 2011-11-07T10:44:00

This is pointer, and all pointers gets the size of IntPtr which is 32-bit on 32-bit systems and and 64-bits on 64-bit systems, all other .NET types have the same size regardless of the instruction-set architecture of target assembly. Also, it's important that the last parameter is of out type.

So, the function prototype will be declared as

VB

Private Shared Function SCardEstablishContext(scope As System.UInt32, reserved1 As System.IntPtr, reserved2 As System.IntPtr, ByRef context As System.IntPtr) As Long

—SA