netusergetinfo/netlocalgroupgetinfo返回错误1722

我有以下代码(vb.net),用于确定给定的帐户名是指本地组还是用户帐户。这将只对计算机上的帐户/组调用,而不是域。

Module netapi
    Private Declare Function NetUserGetInfo Lib "Netapi32.dll" ( _
         ByVal ServerName As String, _
         ByVal UserName As String, _
         ByVal level As Integer, _
         ByRef BufPtr As IntPtr) As Integer

    Private Declare Function NetLocalGroupGetInfo Lib "Netapi32.dll" ( _
         ByVal ServerName As String, _
         ByVal GroupName As String, _
         ByVal level As Integer, _
         ByRef BufPtr As IntPtr) As Integer

    Declare Unicode Function NetApiBufferFree Lib "Netapi32.dll" _
    (ByRef buffer As IntPtr) As Long

    Public Function GetPrincipalType(ByVal MachineName As String, ByVal AccountName As String) As String
        Dim bufPtr As IntPtr
        Dim lngReturn As Integer = NetUserGetInfo("\\" & MachineName, AccountName, 0, bufPtr)
        Console.WriteLine("NetUserGetInfo return value = " & lngReturn)
        Call NetApiBufferFree(bufPtr)
        bufPtr = IntPtr.Zero
        If lngReturn = 0 Then
            Return "User"
        End If
        lngReturn = NetLocalGroupGetInfo("\\" & MachineName, AccountName, 0, bufPtr)
        Console.WriteLine("NetLocalGroupGetInfo return value = " & lngReturn)
        Call NetApiBufferFree(bufPtr)
        bufPtr = IntPtr.Zero
        If lngReturn = 0 Then
            Return "Group"
        End If
        Return "NotFound"
    End Function
End Module

我的问题是netusergetinfo/netlocalgroupgetinfo调用始终返回错误代码1722(RPC服务器不可用)。我已经尝试使用本地计算机名和远程Windows服务器名,在这些服务器上我有管理权限,结果相同。

如果我替换 "\\" & MachineName 具有 Nothing 然后,无论引用的帐户/组是否为 AccountName 实际上存在。

请帮忙。我做错什么了?

更新: 不确定这是否有帮助,但我已经尝试在Win 7和Win XP SP3上运行上述功能。我的编译目标是.NET 4.0客户端框架。