Java Collection in C#

Question

I'm learning some data structures and the language of the course is Java but I'm a C# guy.

Here is the code:

public Collection <Vertex> vertices()
{ 
     return graph.values(); 
}

Vertex is a class but how can I return a Collection in C#? Ty!  

Edit: I don't know if it will help but here is the class Vertex.(Code already in C#) Comments are in german.

public class Vertex : IComparable //Knotenklasse 
{
    public string name; // Name des Knoten
    public List<Edge> edges; // Nachbarn als Kantenliste
    public int nr; // Knotennummer
    public int indegree; // Eingangsgrad
    public bool seen; // Wurde der Knoten schon überprüft? 
    public int dist; // Kosten für den Knoten
    public Vertex prev; // vorheriger Knoten

    public Vertex(string s)
    {
        this.name = s;
        edges = new List<Edge>(); 
    }

    public bool hasEdge(Vertex w)
    {
        foreach (Edge e in edges)
        {
            if(e.dest == w)
            {
                return true;
            }

        }
        return false; 
    }

    public int CompareTo(Vertex d)
    {
       if(this.dist > d.dist)
       {
           return 1;
       }
       else if(this.dist < d.dist)
       {
           return -1;
       }
       else
       {
           return 0; 
       }
    }
}
public class Edge // Kantenklasee
{
    public double cost; // Kosten
    public Vertex dest; // Zeiger auf den nächsten Knoten

    public Edge(Vertex d,double c)
    {
        this.dest = d;
        this.cost = c; 
    }
}

ps: the class graph in C#

public class Graph
{
        private Dictionary<Vertex, string> graph;  
        public Graph(Vertex d, string s)
        {
            graph = new Dictionary<Vertex, string>(); 
        }

}

Answer 1

Dictionary.Values returns a ValueCollection . You can use it directly or convert it to many built in collection types in .NET.

Generally you should return a type that is as general as possible, ie one that knows just enough of the returned data.

public ICollection<Vertex> vertices()
{ 
    return graph.values(); 
}

public IList<Vertex> vertices()
{ 
    return graph.values().ToList(); 
}

ICollection<T> supports Add , Remove and Count .
IList<T> supports Add , Remove , Count and the ability to random access elements by their indexes

If you want to know more about different collection types and when to use them check this link

Answer 2

You can use ICollection<T> which is an generic interface implemented by all the classes from System.Collections.generic :

public ICollection<Vertex> vertices()
{ 
     return graph.values(); 
}