MyMediaLite.DataType.SparseBooleanMatrix.this C# (CSharp) Method

        public ICollection<int> this[int x]
        {
            get	{
                if (x >= row_list.Count)
                    for (int i = row_list.Count; i <= x; i++)
                        row_list.Add(new HashSet<int>());
                return row_list[x];
            }
        }