by Mark S. (5 Submissions)
Category: Windows API Call/Explanation
Compatability: VB 6.0
Difficulty: Unknown Difficulty
Originally Published: Fri 15th February 2002
Date Added: Mon 8th February 2021
Rating: 
(1 Votes)
This class maps network drives to your PC by UNC name. If it exists then it returns the drive letter, otherwise it will use the next available
API Declarations
Private Declare Function WNetCancelConnection Lib "mpr.dll" Alias "WNetCancelConnectionA" (ByVal lpszName As String, ByVal bForce As Long) As Long
Private Declare Function WNetGetConnection Lib "mpr.dll" Alias "WNetGetConnectionA" (ByVal lpszLocalName As String, ByVal lpszRemoteName As String, cbRemoteName As Long) As Long
Private Const MAX_VALUE As Integer = 255
Private Const WN_Access_Denied = &H7
Private Const WN_Already_Connected = &H34
Private Const WN_Bad_Localname = &H33
Private Const WN_Bad_NetName = &H32
Private Const WN_Bad_Password = &H6
Private Const WN_Bad_Pointer = &H4
Private Const WN_Net_Error = &H2
Private Const WN_Not_Supported = &H1
Private Const WN_Out_Of_Memory = &HB
Private Const WN_Success = &H0
Private mstrDriveName As String
Private mstrForceLetter As String
Private mstrUNCName As String
Property Let DriveName(ByVal strDriveName As String)
mstrDriveName = strDriveName
End Property
Property Get DriveName() As String
DriveName = mstrDriveName
End Property
Property Let ForceLetter(ByVal strForceLetter As String)
mstrForceLetter = strForceLetter
End Property
Property Get ForceLetter() As String
ForceLetter = mstrForceLetter
End Property
Property Let UNCName(ByVal strUNCName As String)
mstrUNCName = strUNCName
End Property
Property Get UNCName() As String
UNCName = mstrUNCName
End Property
VBcoders
' These are error descriptions generated by the WNet family of API calls from
' mpr.dll.
Select Case lngErrorCode
Case WN_Not_Supported:
WnetError = "Function is not supported."
Case WN_Out_Of_Memory:
WnetError = "Out of Memory."
Case WN_Net_Error:
WnetError = "An error occurred on the network."
Case WN_Bad_Pointer:
WnetError = "The Pointer was Invalid."
Case WN_Bad_NetName:
WnetError = "Invalid Network Resource Name."
Case WN_Bad_Password:
WnetError = "The Password was Invalid."
Case WN_Bad_Localname:
WnetError = "The local device name was invalid."
Case WN_Access_Denied:
WnetError = "A security violation occurred."
Case WN_Already_Connected:
WnetError = "The local device was connected to a remote resource."
Case Else:
WnetError = "Unrecognized Error " & Str(lngErrorCode) & "."
End Select
End Function
Public Function ConnectUNC(strUNCName As String, strForceLetter As String) As String
Dim boolFound As Boolean
Dim bytDrives As Byte
Dim lngRetCode As Long
Dim lngReturnedUNCName As Long
Dim lngCheck As Long
Dim strDrive As String
Dim strReturnedUNCName As String
On Error GoTo Process_Error
If strUNCName > vbNullString Then
mstrUNCName = strUNCName
mstrForceLetter = strForceLetter
If mstrForceLetter > vbNullString Then
strDrive = Left$(mstrForceLetter, 1) & ":"
lngRetCode = WNetAddConnection(mstrUNCName & Chr$(0), "" & Chr$(0), strDrive & Chr$(0))
If lngRetCode = 0 Then
ConnectUNC = Left$(strDrive, 1)
Else
ConnectUNC = Trim$(mstrUNCName) & " could not be mapped to " & Trim$(mstrForceLetter) & ":."
End If
Else
boolFound = False
For bytDrives = 68 To 90
strDrive = Chr$(bytDrives) & ":"
strReturnedUNCName = Space$(MAX_VALUE)
lngReturnedUNCName = Len(strReturnedUNCName)
lngRetCode = WNetGetConnection(strDrive, strReturnedUNCName, lngReturnedUNCName)
If lngRetCode = 0 Then
lngCheck = InStr(strReturnedUNCName, Chr$(0)) - 1
If LCase$(Left$(strReturnedUNCName, lngCheck)) = LCase$(mstrUNCName) Then
boolFound = True
Exit For
End If
End If
Next bytDrives
' Iterate letters D through Z.
If boolFound Then
ConnectUNC = Left$(strDrive, 1)
Else
For bytDrives = 68 To 90
strDrive = Chr$(bytDrives) & ":"
lngRetCode = WNetAddConnection(mstrUNCName & Chr$(0), "" & Chr$(0), strDrive & Chr$(0))
If lngRetCode = 0 Then
boolFound = True
Exit For
End If
Next bytDrives
If boolFound Then
ConnectUNC = Left$(strDrive, 1)
Else
ConnectUNC = Trim$(mstrUNCName) & " could not be mapped."
End If
End If
End If
Else
ConnectUNC = WnetError(WN_Bad_Localname)
End If
GoTo Process_Continue
Process_Error:
ConnectUNC = WnetError(lngRetCode)
Process_Continue:
End Function
Public Function DisconnectUNC(strDriveName As String) As String
Dim lngRetCode As Long
On Error GoTo Process_Error
If strDriveName > vbNullString Then
mstrDriveName = Left$(strDriveName, 1) & ":"
lngRetCode = WNetCancelConnection(mstrDriveName & Chr$(0), 0)
DisconnectUNC = vbNullString
Else
DisconnectUNC = WnetError(WN_Bad_Localname)
End If
GoTo Process_Continue
Process_Error:
DisconnectUNC = WnetError(lngRetCode)
Process_Continue:
End Function
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