Data hold for graphing data

Graph.cs

public namespace Graphing {
    public class Graph<TX, TY> {
        private readonly List<GraphData<TX, TY>> _data;
        
        public Graph() {
            _data = new List<GraphData<TX, TY>>();
        }

        public GraphData<TX, TY> this[int index] {
            get { return _data[index]; }
        }

        public void Add(GraphData<TX, TY> graph ) {
            this._data.Add(graph);
        }

        public void Add(Dictionary<TX, TY> dictionary ) {
            this._data.Add(new GraphData<TX, TY>(dictionary));
        }

        public TX MaxX { get { return _data.Max(f => f.MaxX); } }
        public TY MaxY { get { return _data.Max(f => f.MaxY); } }

        public TX MinX { get { return _data.Min(f => f.MinX); } }
        public TY MinY { get { return _data.Min(f => f.MinY); } }

    }

    public class GraphData<TX, TY> : IEnumerable<KeyValuePair<TX, TY>> {
        private readonly Dictionary<TX, TY> _data;
        public Color Color { get; set; }
        public GraphType GraphType { get; set; }

        public GraphData() {
            _data = new Dictionary<TX, TY>();
        }

        public GraphData(Dictionary<TX, TY> dictionary) {
            _data = dictionary;
        }

        public TY MaxY { get { return _data.Values.Max(); } }
        public TY MinY { get { return _data.Values.Min(); } }

        public TX MaxX { get { return _data.Keys.Max(); } }
        public TX MinX { get { return _data.Keys.Min(); } }

        public void Add(TX x, TY y) {
            _data.Add(x, y);
        }

        public Dictionary<TX, TY> Data {
            get { return _data; }
        }

        public IEnumerator<KeyValuePair<TX, TY>> GetEnumerator() {
            return _data.AsEnumerable().GetEnumerator();
        }

        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() {
            return _data.AsEnumerable().GetEnumerator();
        }
    }

    public enum GraphType {
        Bar,
        Line,
        Pie
    }
}