Simple Unweighted Undirected in C#

UnweightedUndirected.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Programming.Data_Structures
{
    public class Graph
    {
        public readonly int _V;

        private int _E;

        public LinkedList<int>[] adj;

        public Graph(int V = 0)
        {
            if (V < 0)
                throw new Exception("-ve V");

            this._V = V;

            adj = new LinkedList<int>[V];

            for (int i = 0; i < V; i++)
            {
                adj[i] = new LinkedList<int>();

            }
        }

        public int V()
        {
            return this._V;
        }

        public int E()
        {
            return this._E;
        }

        public void AddEdge(int v, int w)
        {
            if (v < 0 || v >= _V) throw new Exception("Out of bounds");
            if (w < 0 || w >= _V) throw new Exception("Out of bounds");

            bool ExistsInV = adj[v].Contains(w);
            bool ExistsInW = adj[w].Contains(v);

            if ((!ExistsInV) && (!ExistsInW))
            {
                adj[v].AddFirst(w);
                adj[w].AddFirst(v);
                _E++;
            }

        }

        public IEnumerable<int> Adj(int V)
        {
            return adj[V];
        }

        public override String ToString()
        {
            StringBuilder s = new StringBuilder();

            string NEWLINE = Environment.NewLine;

            s.Append(_V + " vertices, " + _E + " edges " + NEWLINE);

            for (int i = 0; i < _V; i++)
            {
                s.Append(i + ": ");

                foreach (int item in adj[i])
                {
                    s.Append(item + " ");
                }

                s.Append(NEWLINE);
            }

            return s.ToString();
        }

    }

}