C#: yield return range/collection

c# .net yield
André Hauptfleisch picture André Hauptfleisch · Mar 24, 2011 · Viewed 12.7k times · Source

I use the yield return keyword quite a bit, but I find it lacking when I want to add a range to the IEnumerable. Here's a quick example of what I would like to do:

IEnumerable<string> SomeRecursiveMethod()
{
    // some code 
    // ...
    yield return SomeRecursiveMethod();
}

Naturally this results in an error, which can be resolved by doing a simple loop. Is there a better way to do this? A loop feels a bit clunky.

Answer

Jon Skeet picture Jon Skeet · Mar 24, 2011

No, there isn't I'm afraid. F# does support this with yield!, but there's no equivalent in C# - you have to use the loop, basically. Sorry... I feel your pain. I mentioned it in one of my Edulinq blog posts, where it would have made things simpler.

Note that using yield return recursively can be expensive - see Wes Dyer's post on iterators for more information (and mentioning a "yield foreach" which was under consideration four years ago...)

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