What is better when using an IEnumerable with one item: yield return or return []?

Question

This is one of those "you can do it many ways" questions. Consider the following code:

protected virtual IEnumerable<ScriptReference> GetScriptReferences()
{
    ScriptReference referece = new ScriptReference();
    referece.Assembly = "FeyenoordEnabled";
    referece.Name = "FeyenoordEnabled.PassTextBox.js";

    return new ScriptReference[] { referece }; 
}

protected virtual IEnumerable<ScriptReference> GetScriptReferences()
{
    ScriptReference referece = new ScriptReference();
    referece.Assembly = "FeyenoordEnabled";
    referece.Name = "FeyenoordEnabled.PassTextBox.js";

    yield return referece;
}

I only need to return one item. The first piece of codes returns an array with a single item and the second one yields the item. What is better and why?

Answer 1

yield is a pretty expensive keyword. You are telling the compiler to do a lot. If performance isn't an issue, go with the more elegant code. But if performance is an issue, stick with the array.

I can say from past experience that getting rid of this type of yield usage has netted me some serious performance gains. But as always, profile and find the real bottlenecks.