/// <summary>
/// Initialise a new Edge when the 'other side' already exists.
/// </summary>
/// <param name="end">The end Vertex of this edge.</param>
/// <param name="otherSide">The 'other side' of this edge.</param>
private Edge(Vertex end, Edge otherSide)
{
this.end = end;
this.otherSide = otherSide;
end.AddEdge(otherSide);
}
/// <summary>
/// Initialise a new Edge
/// </summary>
/// <param name="start">The start Vertex</param>
/// <param name="end">The end Vertex</param>
public Edge(Vertex start, Vertex end)
{
this.end = end;
this.otherSide = new Edge(start, this);
end.AddEdge(otherSide);
}