How to check if IEnumerable is null or empty?

Question

I love string.IsNullOrEmpty method. I'd love to have something that would allow the same functionality for IEnumerable. Is there such? Maybe some collection helper class? The reason I am asking is that in if statements the code looks cluttered if the patter is (mylist != null && mylist.Any()). It would be much cleaner to have Foo.IsAny(myList).

This post doesn't give that answer: IEnumerable is empty?.

Answer 1

Without custom helpers I recommend either ?.Any() ?? false or ?.Any() == true which are relatively concise and only need to specify the sequence once.

---

When I want to treat a missing collection like an empty one, I use the following extension method:

public static IEnumerable<T> OrEmpty<T>(this IEnumerable<T> sequence)
{
    return sequence ?? Enumerable.Empty<T>();
}

This function can be combined with all LINQ methods and foreach, not just .Any(), which is why I prefer it over the more specialized helper functions people are proposing here.

Answer 2

 public static bool AnyNotNull<TSource>(this IEnumerable<TSource> source)
    {
        return source != null && source.Any();
    }

my own extension method to check Not null and Any

Answer 3

This may help

public static bool IsAny<T>(this IEnumerable<T> enumerable)
{
    return enumerable?.Any() == true;
}

public static bool IsNullOrEmpty<T>(this IEnumerable<T> enumerable)
{
    return enumerable?.Any() != true;
}

Answer 4

Starting with C#6 you can use null propagation: myList?.Any() == true

If you still find this too cloggy or prefer a good ol' extension method, I would recommend Matt Greer and Marc Gravell's answers, yet with a bit of extended functionality for completeness.

Their answers provide the same basic functionality, but each from another perspective. Matt's answer uses the string.IsNullOrEmpty-mentality, whereas Marc's answer takes Linq's .Any() road to get the job done.

I am personally inclined to use the .Any() road, but would like to add the condition checking functionality from the method's other overload:

    public static bool AnyNotNull<T>(this IEnumerable<T> source, Func<T, bool> predicate = null)
    {
        if (source == null) return false;
        return predicate == null
            ? source.Any()
            : source.Any(predicate);
    }

So you can still do things like : myList.AnyNotNull(item=>item.AnswerToLife == 42); as you could with the regular .Any() but with the added null check

Note that with the C#6 way: myList?.Any() returns a bool? rather than a bool, which is the actual effect of propagating null

Answer 5

I use this one:

    public static bool IsNotEmpty(this ICollection elements)
    {
        return elements != null && elements.Count > 0;
    }

Ejem:

List<string> Things = null;
if (Things.IsNotEmpty())
{
    //replaces ->  if (Things != null && Things.Count > 0) 
}

Answer 6

public static bool IsNullOrEmpty<T>(this IEnumerable<T> enumerable) {
    return enumerable == null || !enumerable.Any();
}