Graph in C#

using System;
using System.Collections.Generic;

public class Graph
{
   List<int>[] adj;
   int V;

   public Graph(int vertices)
   {
       V = vertices;
       adj = new List<int>[V];
       for(int i = 0; i < V; i++)
       {
           adj[i] = new List<int>();
       }
   }

   public void AddEdge(int from, int to)
   {
       adj[from].Add(to);
       // adj[to].Add(from);
   }

   public int Size()
   {
       return V;
   }

   public List<int> GetEdges(int vertex)
   {
       if (vertex > V) return null;
       return adj[vertex];
   }
}