The AdjacencyGraph<TVertex, TEdge>, also known as adjacency list provides an efficient data structure to access the out-edges of a vertex.

This class is mutable, serializable, cloneable and can be constructed in many different ways. Internally, the data structure keeps a dictionary from TVertex to a unordered list of TEdge elements.

var graph = new AdjacencyGraph<int, Edge<int>>();
...
foreach(int vertex in graph.Vertices)
{
    foreach(Edge<int> edge in graph.OutEdges(vertex))
    {
        Console.WriteLine(edge);
    }
}

If you need to access in-edges as well, consider using the BidirectionalGraph.