Cached Property: Easier way?

Question

I have a object with properties that are expensive to compute, so they are only calculated on first access and then cached.

 private List notes;
         


        

Answer 1

In .NET 3.5 or earlier, what you have is a very standard practice, and a fine model.

(Although, I would suggest returning IList, or IEnumerable if possible, instead of List in your public API - List should be an implementation detail...)

In .NET 4, however, there is a simpler option here: Lazy. This lets you do:

private Lazy> notes;
public IEnumerable Notes
{
    get
    {
        return this.notes.Value;
    }
}

// In constructor:
this.notes = new Lazy>(this.CalcNotes);