Question

I have an Object called Graph.

I have list of Vertices in Graph class. So the Class would somewhat look like this. Its a .Net 2.0 code.

public class Graph
{
    public List<Vertex> Vertices 
    {
        get{ return _vertices}
    }
} private List<Vertex> _vertices;

Here is my question. I would like to validate the Vertex object (by calling Vertex.IsValid() method) before adding it to the Graph object.

What’s the best way to do it? I like the way we add code inside the property’s getter block. Is there any similar way to it?

I have workarounds, but would like to do it in the best way possible.

Answer 1

The best solution is to not expose the list of vertices as a mutable list. Instead, if you need a Vertices property, make it return a read-only data-structure. Then, just include an Add() method, and validate all you want:

public ReadOnlyCollection<Vertex> Vertices
{
    get { return _vertices.AsReadOnly(); }
}

public void Add(Vertex vertex)
{
    if (vertex.IsValid())
        _vertices.Add(vertex);
}