HOWTO: Call WNetConnectionDialog1 and WNetDisconnectDialog1

• Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0
• Microsoft Windows 95
• Microsoft Windows NT versions 3.51, 4.0
• Microsoft Win32 Software Development Kit (SDK)

SUMMARY

The functions WNetConnectionDialog1 and WNetDisconnectDialog1 are very useful for connecting and disconnecting from remote resources. The functions take parameters that allow you to change the default values of the connect and disconnect dialogs before calling them.

They also provide a common set of error-handling messages to the user automatically.

This article demonstrates how to use some of these functions from 32-Bit Visual Basic. These functions are available on Windows NT, Windows 95, and Windows 98.

MORE INFORMATION

The hardest part of getting these functions working is getting the strings and the NETRESOURCE structure setup in the CONNECTDLGSTRUCT. Fortunately, there are only a few strings in the DISCDLGSTRUCT structure.

1. Create a new project with two CommandButtons on the main form.



2. Name the buttons cmdConnectDlg and cmdDisconnectDlg.



3. Add a Textbox to the form and name it txtDisconnect.



4. Place the following code in the form:

   
         Option Explicit
   
         Private Const CONNDLG_RO_PATH = &H1    'Resource path should be
                                                'read-only.
         Private Const CONNDLG_CONN_POINT = &H2 'Netware-style movable
                                                'connection-point enabled.
         Private Const CONNDLG_USE_MRU = &H4    'Use MRU combobox
         Private Const CONNDLG_HIDE_BOX = &H8   'Hide persistent connect
                                                'check box.
         '/*
         ' * NOTE:  Set, at most, one of the below flags. If neither flag is
         ' *        set, then the persistence is set to whatever the user
         ' *        chose during a previous connection.
         '
         Private Const CONNDLG_PERSIST = &H10     'Force persistent
                                                  'connection.
         Private Const CONNDLG_NOT_PERSIST = &H20 'Persistent not allowed.
         ' */ 
   
         Private Const DISC_UPDATE_PROFILE = &H1  'Remove persistent
                                                  'connection.
         Private Const DISC_NO_FORCE = &H40       'Don't force the disconnect
                                                  'if files are still open.
         Private Const RESOURCETYPE_DISK = &H1
         Private Const NO_ERROR = 0
         Private Const WN_SUCCESS = NO_ERROR
   
         Private Declare Function MapDrive Lib "mpr.dll" Alias _
            "WNetConnectionDialog1A" ( _
            lpConnectDlgStruct As Any) As Long
         Private Declare Function UnMapDrive Lib "mpr.dll" Alias _
            "WNetDisconnectDialog1A" ( _
            lpDiscDlgStruct As Any) As Long
   
         Private Type CONNECTDLGSTRUCT
            cbStructure As Long
            hwndOwner As Long
            lpConnRes As Long
            dwFlags As Long
            dwDevNum As Long
         End Type
   
         Private Type DISCDLGSTRUCT
            cbStructure As Long
            hwndOwner As Long
            lpLocalName As String
            lpRemoteName As String
            dwFlags As Long
         End Type
   
         Private Type NETRESOURCE
            dwScope As Long
            dwType As Long
            dwDisplayType As Long
            dwUsage As Long
            lpLocalName As Long
            lpRemoteName As String
            lpComment As Long
            lpProvider As Long
         End Type
   
         'Memory Management Routines & Constants
         Private Const GMEM_FIXED = &H0
         Private Const GMEM_ZEROINIT = &H40
         Private Const GPTR = (GMEM_FIXED Or GMEM_ZEROINIT)
         Private Declare Function GlobalAlloc Lib "kernel32" ( _
            ByVal wFlags As Long, _
            ByVal dwBytes As Long) As Long
         Private Declare Function GlobalFree Lib "kernel32" ( _
            ByVal hMem As Long) As Long
         Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" _
            (lpOut As Any, _
            lpIn As Any, _
            ByVal cbCopy As Long)
   
         Private Sub cmdConnectDlg_Click()
            Dim cs As CONNECTDLGSTRUCT, nr As NETRESOURCE, res As Long
            'Setup the NETRESOURCE structure.
            nr.lpRemoteName = "\\servername\sharename"
            nr.dwType = RESOURCETYPE_DISK
   
            With cs 'Setup the connection dialog structure.
               .cbStructure = LenB(cs)
               .hwndOwner = Me.hWnd
               .lpConnRes = GlobalAlloc(GPTR, LenB(nr))
               CopyMemory ByVal .lpConnRes, nr, LenB(nr)
               .dwFlags = CONNDLG_USE_MRU Or _
                          CONNDLG_HIDE_BOX Or _
                          CONNDLG_NOT_PERSIST
            End With
   
            res = MapDrive(cs) 'Call WNetConnectionDialog1.
            If res = WN_SUCCESS Then
               MsgBox "MapDrive Succeeded."
               txtDisconnect.Text = Chr$(cs.dwDevNum + 64) & ":"
            Else
               MsgBox "Error: " & Err.LastDllError
            End If
            GlobalFree (cs.lpConnRes)
         End Sub
   
         Private Sub cmdDisconnectDlg_Click()
            Dim ds As DISCDLGSTRUCT, res As Long
            'Setup the disconnect dialog structure.
            ds.cbStructure = LenB(ds)
            ds.hwndOwner = Me.hWnd
            ds.lpLocalName = txtDisconnect.Text
            ds.dwFlags = DISC_NO_FORCE Or DISC_UPDATE_PROFILE
   
            res = UnMapDrive(ds) 'Call WnetDisconnectDialog1.
            If res = WN_SUCCESS Then
               MsgBox "UnMapDrive Succeeded."
            Else
               MsgBox "Error: " & Err.LastDllError
            End If
         End Sub
    




5. Execute the program. Click the cmdConnectDlg button, and connect to a network share. The drive letter that is connected is placed in the txtDisconnect text box. Now click the cmdDisconnectDlg button. The mapped drive will be disconnected.



6. Click the cmdDisconnectDlg button again: On Windows NT, an error will be displayed and then the error value will be returned by the WNetDisconnectDialog1 function.



7. Click the cmdConnectDlg button, and pass an invalid server name to the dialog. Another error message will appear explaining the problem and, again, passing the error back to the program.

Keywords : kbNTOS351 kbNTOS400 kbVBp500 kbVBp600 kbWinOS95 kbWNet kbGrpVB
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Issue type : kbhowto