c# - Yield Return with Null

Question

Is there any way to optionally return a null with a "return yield" driven iterator?

I would like to return a null in some cases and I don't think this is particular to IEnumerable of type string. Same goes for IEnumerable of type int etc. Thanks

static void Main(string[] args)
{
    var Items = GetItems();

    if (Items != null)
    {
        foreach (var item in Items)
        {
            Console.WriteLine(item);
        }
    }
    else
    {
        Console.WriteLine("<null>");
    }
}

static IEnumerable<string> GetItems()
{
    if (false)
    {
        yield return "Andy";
        yield return "Jennifer";
    }

    return null; // <- Compiler Error:
    // Cannot return a value from an iterator. 
    // Use the yield return statement to return a value,
    // or yield break to end the iteration.
}

Answer 1

If you need to things like that (or throw things like ArgumentException immediately), you need to separate your iterator into two methods:

 public IEnumerable<string> GetItems() {
     if (something) return null;
     return GetItemsInternal();
 }

 private IEnumerable<string> GetItemsInternal() {
     // the actual iterator with "yield return" goes here.
 }