GraphLibrary/DrawGraph/Edge.cs

using System.Drawing;
using System.Windows.Shapes;

namespace DrawGraph
{
    public class Edge
    {
        public Line Line { get; }
        public ArrowLine ArrowLine { get; }
        public Vertex StartVertex { get; }
        public Vertex FinishVertex { get; }
        public int? Weight { get; set; }
        public bool IsFocused { get; }

        public Edge(Line line, Vertex v1, Vertex v2)
        {
            Line = line;
            StartVertex = v1;
            FinishVertex = v2;
            IsFocused = false;
        }

        public Edge(ArrowLine line, Vertex v1, Vertex v2)
        {
            ArrowLine = line;
            StartVertex = v1;
            FinishVertex = v2;
            IsFocused = true;
        }

        public Edge(Line line, Vertex v1, Vertex v2, int weight)
        {
            Line = line;
            StartVertex = v1;
            FinishVertex = v2;
            Weight = weight;
            IsFocused = false;
        }
        public Edge(ArrowLine line, Vertex v1, Vertex v2, int weight)
        {
            ArrowLine = line;
            StartVertex = v1;
            FinishVertex = v2;
            IsFocused = true;
            Weight = weight;

            ArrowLine.X1 = v1.CenterByX;
            ArrowLine.X2 = v2.CenterByX;
            ArrowLine.Y1 = v1.CenterByY;
            ArrowLine.Y2 = v2.CenterByY;
            ArrowLine.StrokeThickness = 2;
        }

        public static double GetCenterByX(Edge edge)
        {
            var x = (edge.FinishVertex.X + edge.StartVertex.X) / 2;
            return x;
        }

        public static double GetCenterByY(Edge edge)
        {
            var y = (edge.FinishVertex.Y + edge.StartVertex.Y) / 2;
            return y;
        }

        public static bool IsCursorOnVertex(Point cursorPosition, Vertex vertex)
        {
                if (vertex.CenterByX - cursorPosition.X <= Settings.VertexWidth / 2 &&
                    vertex.CenterByX - cursorPosition.X >= 0)
                {
                    if (vertex.CenterByY - cursorPosition.Y <= Settings.VertexHeight / 2 &&
                        vertex.CenterByY - cursorPosition.Y >= 0)
                    {
                        return true;
                    }
                }

                if (cursorPosition.X - vertex.CenterByX <= Settings.VertexWidth / 2 &&
                    cursorPosition.X - vertex.CenterByX >= 0)
                {
                    if (cursorPosition.Y - vertex.CenterByY <= Settings.VertexWidth / 2 &&
                        cursorPosition.Y - vertex.CenterByY >= 0)
                    {
                        return true;
                    }

                    return false;
                }

                return false;
        }

        public static bool IsVertexBelongToEdge(Edge edge, Vertex vertex)
        {
            if (Vertex.Compare(vertex, edge.StartVertex) || Vertex.Compare(vertex, edge.FinishVertex))
                return true;

            return false;
        }
    }
}