How to switch users?

How to switch from users A to user B in visual basic?
User A should not log off.
Please help.

[EDIT]


This link may have some info?
http://support.microsoft.com/?kbid=841291

I use this code that i found on the page of the link you gave to me, but it does nothing :(

Please help!!!

Code:

---

Imports System.Runtime.InteropServices

Public Class Form1
    'Constant declarations that you can use for message processing follow:
    '
    Private Const _WIN32_WINNT As Int32 = &H501
    Private Const NOTIFY_FOR_THIS_SESSION As Int32 = &H0
    Private Const WM_WTSSESSION_CHANGE As Int32 = &H2B1
    Private Const WTS_CONSOLE_CONNECT As Int32 = &H1
    Private Const WTS_CONSOLE_DISCONNECT As Int32 = &H2
    Private Const WTS_SESSION_LOCK As Int32 = &H7
    Private Const WTS_SESSION_UNLOCK As Int32 = &H8
    Private Const WM_DESTROY As Int32 = &H2
    Private Const WM_ACTIVATEAPP As Int32 = &H1C
   
    'Declaration of API functions that you can use for message processing follow:
    '
    'The WTSUnRegisterSessionNotification function unregisters the specified
    'window so that the specified window receives no more session-change notifications.
    <DllImport("Wtsapi32.dll")> _
    Private Shared Function WTSUnRegisterSessionNotification( _
    ByVal hWnd As IntPtr) As Boolean

    End Function
    'The WTSRegisterSessionNotification function registers the specified
    'window to receive session-change notifications.
    <DllImport("Wtsapi32.dll")> _
    Private Shared Function WTSRegisterSessionNotification( _
    ByVal hWnd As IntPtr, ByVal dwFlags As Int32) As Boolean

    End Function
    'The PostQuitMessage function indicates to the system that a thread
    'has made a request to quit. The PostQuitMessage function is typically used in
    'response to a WM_DESTROY message.
    <DllImport("user32.dll")> _
    Private Shared Sub PostQuitMessage( _
    ByVal nExitCode As Int32)

    End Sub
    'The OpenIcon function restores a minimized (iconic) window to its
    'previous size and previous position. The OpenIcon function then activates the window.
    <DllImport("user32.dll")> _
    Private Shared Function OpenIcon(ByVal hwnd As IntPtr) As Boolean

    End Function
    'The SetForegroundWindow function puts the thread that created the
    'specified window in the foreground and then activates the window.
    <DllImport("user32.dll")> _
    Private Shared Function SetForegroundWindow(ByVal hwnd As IntPtr) As Boolean

    End Function
 




    '
    'The following processes Windows messages:
    '
    <System.Security.Permissions.PermissionSetAttribute _
    (System.Security.Permissions.SecurityAction.Demand, Name:="FullTrust")> _
    Protected Overrides Sub WndProc(ByRef m As Message)        '
        Select Case (m.Msg)
            '
            Case WM_WTSSESSION_CHANGE

                Select Case (m.WParam.ToInt32)
                    Case WTS_CONSOLE_CONNECT
                        MessageBox.Show("WTS_CONSOLE_CONNECT", "WM_SESSION_CHANGE", MessageBoxButtons.OK)
                    Case WTS_CONSOLE_DISCONNECT
                        MessageBox.Show("WTS_CONSOLE_DISCONNECT", "WM_SESSION_CHANGE", MessageBoxButtons.OK)
                    Case WTS_SESSION_LOCK
                        MessageBox.Show("WTS_SESSION_LOCK", "WM_SESSION_CHANGE", MessageBoxButtons.OK)
                    Case WTS_SESSION_UNLOCK
                        MessageBox.Show("WTS_SESSION_UNLOCK", "WM_SESSION_CHANGE", MessageBoxButtons.OK)
                    Case Else
                        MessageBox.Show("test", "test", MessageBoxButtons.OK)
                End Select
                '             
        End Select
        '
        MyBase.WndProc(m)
        '
    End Sub
    '
    Protected Overrides Sub OnHandleCreated(ByVal e As System.EventArgs)
        '
        'The WTSRegisterSessionNotification function registers the specified
        'window to receive session-change notifications.
        '
        WTSRegisterSessionNotification(Me.Handle, NOTIFY_FOR_THIS_SESSION)
        '
        MyBase.OnHandleCreated(e)
        '
    End Sub
    '
    Protected Overrides Sub OnHandleDestroyed(ByVal e As System.EventArgs)
        '
        WTSUnRegisterSessionNotification(Me.Handle)
        PostQuitMessage(0)
        '
    End Sub
    '







    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
        '
        Dim blnChk As Boolean
        '
        'Checking for the existence of an
        'application that is already running.
        '
        If UBound(Diagnostics.Process.GetProcessesByName _
        (Diagnostics.Process.GetCurrentProcess.ProcessName)) > 0 Then
            '
            'Checking if there is already
            'an instance that is running in this user's session.
            '
            blnChk = ActivatePrevInstance("FastSwitchingForm")
            '
            If (blnChk = False) Then
                MsgBox("Another instance of " & _
                Diagnostics.Process.GetCurrentProcess.ProcessName & _
                " is already running in another user's session on this computer." & _
                " You cannot run two instances at a time. You must use the other instance.")
                End
            End If
            '
        End If
        '
    End Sub

    '
    'This is a function to verify whether the application is already running.
    'If the application is already running, set the focus on the application.
    '
    Private Function ActivatePrevInstance(ByVal argStrAppToFind As String) As Boolean
        '
        Dim PrevHndl As IntPtr = Nothing
        Dim result As Boolean
        Dim objProcess As New Process() 'This is a variable to hold an individual process.
        Dim objProcesses() As Process 'This is a collection of all the processes that are running on the local computer.
        '
        objProcesses = Process.GetProcesses() 'Get all processes into the collection.()
        '
        For Each objProcess In objProcesses
            '
            'Check and then exit if there is an application that is already running.
            '
            If UCase(objProcess.MainWindowTitle) = UCase(argStrAppToFind) Then
                MsgBox("Another instance of " & argStrAppToFind & _
                " is already running on this computer. " & _
                "You cannot run two instances at a time." & _
                " You must use the other instance.")
                PrevHndl = objProcess.MainWindowHandle
                Exit For
            End If
        Next
        '
        If PrevHndl.Equals(IntPtr.Zero) Then
            ActivatePrevInstance = False
            Exit Function 'If no previous instance is found, exit the application.
        Else
            ActivatePrevInstance = True
        End If
        '
        result = OpenIcon(PrevHndl) 'Restore the program.
        result = SetForegroundWindow(PrevHndl) 'Activate the application.
        End 'End the current instance of the application.
        '
    End Function
    '



End Class

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can anybody help me?