HOWTO: Call WNetConnectionDialog1 and WNetDisconnectDialog1

• Microsoft Visual Basic Professional Edition for Windows, version 5.0
• 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 both Windows NT and Windows 95.

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 checkbox
      '/*
      ' * 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          : vb5all vb5howto
Version           : WINDOWS:5.0,95; WINNT:3.51,4.0
Platform          : WINDOWS winnt
Issue type        : kbhowto