[DllImport("advapi32.dll", EntryPoint = "GetLengthSid", CharSet = CharSet.Auto)]

    static extern int GetLengthSid(IntPtr pSID);

                int size = (int)GetLengthSid(SID_ptr);

        uint length = UnsafeNativeMethods.GetLengthSid(pSid);

    static extern int GetLengthSid(

                    int size = (int)GetLengthSid(iter);

static extern uint GetLengthSid(IntPtr pSid);

    Public Declare Function GetLengthSid Lib "advapi32.dll"( _

        int length = (int) GetLengthSid(pSid);