System.Collections.SortedList.SyncSortedList.this C# (CSharp) Метод

            public override Object this[Object key]
            {
                get
                {
                    lock (_root)
                    {
                        return _list[key];
                    }
                }
                set
                {
                    lock (_root)
                    {
                        _list[key] = value;
                    }
                }
            }