System.Security.AccessControl.Privilege.LuidFromPrivilege C# (CSharp) Method

        private static Luid LuidFromPrivilege(string privilege)
        {
            Luid luid;
            luid.LowPart = 0;
            luid.HighPart = 0;

            //
            // Look up the privilege LUID inside the cache
            //

            try
            {
                privilegeLock.EnterReadLock();

                if (luids.ContainsKey(privilege))
                {
                    luid = luids[privilege];

                    privilegeLock.ExitReadLock();
                }
                else
                {
                    privilegeLock.ExitReadLock();

                    if (false == Interop.Advapi32.LookupPrivilegeValue(null, privilege, out luid))
                    {
                        int error = Marshal.GetLastWin32Error();

                        if (error == Interop.Errors.ERROR_NOT_ENOUGH_MEMORY)
                        {
                            throw new OutOfMemoryException();
                        }
                        else if (error == Interop.Errors.ERROR_ACCESS_DENIED)
                        {
                            throw new UnauthorizedAccessException();
                        }
                        else if (error == Interop.Errors.ERROR_NO_SUCH_PRIVILEGE)
                        {
                            throw new ArgumentException(
                                SR.Format(SR.Argument_InvalidPrivilegeName,
                                privilege));
                        }
                        else
                        {
                            System.Diagnostics.Debug.Assert(false, string.Format(CultureInfo.InvariantCulture, "LookupPrivilegeValue() failed with unrecognized error code {0}", error));
                            throw new InvalidOperationException();
                        }
                    }

                    privilegeLock.EnterWriteLock();
                }
            }
            finally
            {
                if (privilegeLock.IsReadLockHeld)
                {
                    privilegeLock.ExitReadLock();
                }

                if (privilegeLock.IsWriteLockHeld)
                {
                    if (!luids.ContainsKey(privilege))
                    {
                        luids[privilege] = luid;
                        privileges[luid] = privilege;
                    }

                    privilegeLock.ExitWriteLock();
                }
            }

            return luid;
        }

 public Privilege(string privilegeName)
 {
     if (privilegeName == null)
     {
         throw new ArgumentNullException("privilegeName");
     }
     this.luid = Privilege.LuidFromPrivilege(privilegeName);
 }