Salut, j'ai un bout de code en VB6, tu dois pouvoir l'adapter en .NET :

Option Explicit

'**************
' UTILISATION
'Dim variable as integer
'Dim essai As String
'essai = "\\UnPC\RessourcePartagée"

    'to add a connection call by:
    'variable = AddConnection(essai, "MyPwd", "z:")
    'To cancel a connection type:
    'variable = CancelConnection("z:", 1)
'**************

Private Declare Function WNetAddConnection Lib "mpr.dll" Alias "WNetAddConnectionA" (ByVal lpszNetPath As String, ByVal lpszPassword As String, ByVal lpszLocalName As String) As Long
Private Declare Function WNetCancelConnection Lib "mpr.dll" Alias "WNetCancelConnectionA" (ByVal lpszName As String, ByVal bForce As Long) As Long

Const WN_SUCCESS = 0 ' The function was successful.
Const WN_NET_ERROR = 2 ' An error occurred on the network.
Const WN_BAD_PASSWORD = 6 ' The password was invalid.

Private Declare Function WNetConnectionDialog Lib "mpr.dll" (ByVal hwnd As Long, _
                                                            ByVal dwType As Long) As Long
Private Declare Function WNetDisconnectDialog Lib "mpr.dll" (ByVal hwnd As Long, _
                                                            ByVal dwType As Long) As Long
Const RESOURCETYPE_DISK = &H1
Const RESOURCETYPE_PRINT = &H2

Function AddConnection(MyShareName As String, MyPWD As String, UseLetter As String) As Integer
    On Local Error GoTo AddConnection_Err
    AddConnection = WNetAddConnection(MyShareName, MyPWD, UseLetter)
AddConnection_End:
    Exit Function
AddConnection_Err:
    AddConnection = Err
    MsgBox Error$
    Resume AddConnection_End
End Function

Function CancelConnection(DriveLetter As String, Force As Integer) As Integer
    On Local Error GoTo CancelConnection_Err
    CancelConnection = WNetCancelConnection(DriveLetter, Force)
CancelConnection_End:
    Exit Function
CancelConnection_Err:
    CancelConnection = Err
    MsgBox Error$
    Resume CancelConnection_End
End Function

Function Lettre() As String
    Dim i As Integer
    'Dim test
    For i = 90 To 70 Step -1 'de Z à E
        'test = Chr(i)
        On Error Resume Next
      If Dir(Chr(i) & ":\", vbDirectory) = "" Then
        If Err.Number = 0 Then
            Lettre = Chr(i) & ":"
            Exit For
        End If
      End If
        On Error GoTo 0
    Next
End Function

Function AddConnection_Dialog() As Long
'Dim x As Long
'Connecter un lecteur réseau
AddConnection_Dialog = WNetConnectionDialog(0, RESOURCETYPE_DISK)
'Déconnecter un lecteur réseau
'x = WNetDisconnectDialog(Me.hwnd, RESOURCETYPE_DISK)
'Connecter une imprimante
'x = WNetConnectionDialog(Me.hwnd, RESOURCETYPE_PRINT)
'Déconnecter une imprimante
'x = WNetDisconnectDialog(Me.hwnd, RESOURCETYPE_PRINT)
End Function