Is it better to yield return lookup lists or preload a static list in c#?

Question

I have a simple lookup list that I will use to populate a dropdown in Silverlight. In this example I'm using US States.

I'm trying to figure out if its better to return a static list or use the yield keyword. Of the following two pieces of code, which is the preferred and why?

Version 1: Using yield return

public class States
{
    public static IEnumerable<string> GetNames()
    {
        yield return "Alabama"; 
        yield return "Alaska";
        yield return "Arizona";
        yield return "Arkansas";
        yield return "California";
        yield return "Others ...";
    }
}

Version 2: Return the list

public class States
{
    private static readonly IList<string> _names;

    static States()
    {
        _names = new List<string>() {"Alabama", 
                                     "Alaska",
                                     "Arizona",
                                     "Arkansas",
                                     "California",
                                     "Others ..." };

    }

    public static IList<string> GetNames()
    {
        return _names;
    }
}

Thomas Levesque Thomas Levesque · Accepted Answer · 2009-08-25T23:32:33

The question you need to ask yourself is : "do I want the code that calls GetNames to be able to modify the list ?"

If the answer is yes, return a IList, implicitly saying : "read-write"
If the answer is no, return a IEnumerable, implicitly saying : "read-only"

Anyway, I think you should put the state names in a resource file, rather than hard-coding them (even though that list is unlikely to change in the short term...)

Here is what I would do :

public static IEnummerable<string> GetNames()
{
    foreach(string name in _names) yield return name;
}

This way you don't directly expose the list to the "outside world"

Is it better to yield return lookup lists or preload a static list in c#?

3 Answers