public TrisEdge(Tris tris, TrisVertex a, TrisVertex b)
{
this.tris = tris;
A = a;
B = b;
_idx = b.Position.X - a.Position.X;
_idy = b.Position.Y - a.Position.Y;
}
public Tris FindAnotherTrisWith(Tris tris, TrisVertex a, TrisVertex b)
{
return(Trises.Find(f => f != tris && f.HasEdge(a, b)));
}