C# Signature:

[DllImport("netapi32.dll", SetLastError=true, CharSet=CharSet.Unicode)]
static extern int NetFileEnum(
     string servername,
     string basepath,
     string username,
     int level,
     ref IntPtr bufptr,
     int prefmaxlen,
     out int entriesread,
     out int totalentries,
     IntPtr resume_handle
);

VB Signature:

Declare Unicode Function NetFileEnum Lib "netapi32.dll" ( _
    ByVal servername As String, _
    ByVal basepath As String, _
    ByVal username As String, _
    ByVal level As Integer, _
    ByRef bufptr As IntPtr, _
    ByVal prefmaxlen As Integer, _
    ByRef entriesread As Integer, _
    ByRef totalentries As Integer, _
    ByVal resume_handle As IntPtr) As Integer

User-Defined Types:

FILE_INFO_3

Notes:

Definition from the API

    'NET_API_STATUS NetFileEnum(
    '  LPWSTR servername,
    '  LPWSTR basepath,
    '  LPWSTR username,
    '  DWORD level,
    '  LPBYTE* bufptr,
    '  DWORD prefmaxlen,
    '  LPDWORD entriesread,
    '  LPDWORD totalentries,
    '  PDWORD_PTR resume_handle
    ');

Tips & Tricks:

You must free the memory allocated to the bufptr with the NetApiBufferFree function

C# Sample Code:

    const int MAX_PREFERRED_LENGTH = -1;

    int dwReadEntries;
    int dwTotalEntries;
    IntPtr pBuffer = IntPtr.Zero ;
    FILE_INFO_3 pCurrent = new FILE_INFO_3();

    int dwStatus = NetFileEnum(null, null, null, 3, ref pBuffer, MAX_PREFERRED_LENGTH, out dwReadEntries, out dwTotalEntries, IntPtr.Zero );

    if (dwStatus == 0) {
    for (int dwIndex=0; dwIndex < dwReadEntries; dwIndex++) {

        IntPtr iPtr = new IntPtr(pBuffer.ToInt32() + (dwIndex * Marshal.SizeOf(pCurrent)));            
        pCurrent = (FILE_INFO_3) Marshal.PtrToStructure(iPtr, typeof(FILE_INFO_3));

        Console.WriteLine("dwIndex={0}", dwIndex);
        Console.WriteLine("    id={0}", pCurrent.fi3_id );
        Console.WriteLine("    num_locks={0}", pCurrent.fi3_num_locks );
        Console.WriteLine("    pathname={0}", pCurrent.fi3_pathname );
        Console.WriteLine("    permission={0}", pCurrent.fi3_permission );
        Console.WriteLine("    username={0}", pCurrent.fi3_username  );

    }

    NetApiBufferFree(pBuffer);

    }

VB.Net Sample Code:

    Const MAX_PREFERRED_LENGTH As Integer = -1
    Dim dwIndex, dwStatus, dwReadEntries, dwTotalEntries As Integer
    Dim pCurrent As FILE_INFO_3
    Dim iPtr, pBuffer As IntPtr

    dwStatus = NetFileEnum(TextBox1.Text, Nothing, Nothing, 3, pBuffer, MAX_PREFERRED_LENGTH, dwReadEntries, dwTotalEntries, IntPtr.Zero)
    if dwStatus = 0 then
        For dwIndex = 0 To dwReadEntries - 1

        iPtr = New IntPtr(pBuffer.ToInt32 + (dwIndex * Marshal.SizeOf(pCurrent)))
        pCurrent = CType(Marshal.PtrToStructure(iPtr, GetType(FILE_INFO_3)), FILE_INFO_3)

        Debug.WriteLine("dwIndex=" & dwIndex)
        Debug.WriteLine("   id: " & pCurrent.fi3_id)
        Debug.WriteLine("   num_locks: " & pCurrent.fi3_num_locks)
        Debug.WriteLine("   pathname: " & pCurrent.fi3_pathname)
        Debug.WriteLine("   permission: " & pCurrent.fi3_permission)
        Debug.WriteLine("   username: " & pCurrent.fi3_username)
        Next
     end if

Alternative Managed API:

Do you know one? Please contribute it!