Clean way to go from IEnumerable to IEnumerable in a project with nullable reference types enabled

Asked Dec 26 '21 at 15:48

Active Dec 26 '21 at 16:09

Viewed 273 times

When processing the elements of a JsonArray with linq, the signature is IEnumerable<JsonNode?>. So I was trying to come up with a clean filter that would only select the non-null elements. .Where(x => x!=null) does not work because the signature is still IEnumerable<JsonNode?> after that (resulting in warnings).

The following extension method does work, but is there a less clunky way to achieve the same?

public static class IEnumerableExtensions
{
    public static IEnumerable<T> NotNull<T>(this IEnumerable<T?> seq) where T : class 
    {
        foreach(var v in seq)
        {
            if(v != null) yield return v;
        }
    }
}

asked Dec 26 '21 at 15:48

jmik

1

I'm not sure this will work, but how about `.Where(x => x.HasValue).Select(x => x.Value)`? – Ron Beyer Dec 26 '21 at 15:52
@RonBeyer it surely won't cause `where T : class` – Guru Stron Dec 26 '21 at 15:56
@RonBeyer unfortunately nullable refs don't have those properties – jmik Dec 26 '21 at 15:57
1

Try using `Where(i => i != null)!` (i.e. end with null forgiving operator) – Guru Stron Dec 26 '21 at 16:00
@GuruStron tried it, the output signature is still `IEnumerable` after that – jmik Dec 26 '21 at 16:05
@GuruStron But that was a good tip.. this works: `.Where(x => x != null).Select(x => x!)` – jmik Dec 26 '21 at 16:08
1

@jmik I meant to use it in your extension method. Your solution supposed to be my next "inline" suggestion) – Guru Stron Dec 26 '21 at 21:57

Clean way to go from IEnumerable to IEnumerable in a project with nullable reference types enabled

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