///<summary>Creates an instance of the Lsa class for the specified computerName.</summary>
        public Lsa(string computerName)
        {
            try
            {
                LSA_OBJECT_ATTRIBUTES lsaAttr = new LSA_OBJECT_ATTRIBUTES();
                lsaAttr.Length = Marshal.SizeOf(typeof(LSA_OBJECT_ATTRIBUTES));

                LSA_UNICODE_STRING computer = ConvertToLsaUnicodeString(computerName);

                uint ntStatus = UnsafeNativeMethods.LsaOpenPolicy(
                    computer,
                    ref lsaAttr,
                    (int)LsaPolicyAccess.POLICY_ALL_ACCESS,
                    out lsaHandle
                    );
                TestNtStatus(ntStatus);
            }
            catch
            {
                throw;
            }
        }
 internal static extern uint LsaOpenPolicy(
     LSA_UNICODE_STRING SystemName,
     ref LSA_OBJECT_ATTRIBUTES ObjectAttributes,
     int AccessMask,
     out IntPtr PolicyHandle
     );