System.Linq.Enumerable: Add IsNullOrEmpty()

[tvardero]

Originally posted here: dotnet/csharplang#6572

Proposing to add this to System.Linq.Enumerable class:

public bool IsNullOrEmpty([NotNullWhen(false)] IEnumerable? value);

Idea behind: having string.IsNullOrEmpty() for everything enumerable.

Could come in handy:

IEnumerable<object>? nullCollection = (List<object>)null;
IEnumerable<object>? emptyCollection = Array.Empty<object>();
IEnumerable<object>? notEmptyCollection = (IEnumerable<object>)(IEnumerable<char>)"something";

// Existing solution:
bool a1 = nullCollection == null || !nullCollection.Any(); // true
bool b1 = emptyCollection == null || !emptyCollection.Any(); // true
bool c1 = notEmptyCollection = null || !notEmptyCollection.Any(); // false

// Proposed:
bool a2 = Enumerable.IsNullOrEmpty(nullCollection); // true
bool b2 = Enumerable.IsNullOrEmpty(emptyCollection); // true
bool c2 = Enumerable.IsNullOrEmpty(notEmptyCollection); // false

// Also speaking of System.String class:
_ = string.IsNullOrEmpty("something") == Enumerable.IsNullOrEmpty("something");
_ = string.IsNullOrWhiteSpace("something") == Enumerable.IsNullOrEmpty("something".Trim());

[EgorBo]

Related: #32642

[tvardero]

Thank you. As we know, Array also is IEnumerable, so my proposal also covers those. As well as String, as latter is just IEnumerable of chars with some salt and pepper.

I don't propose, however, to change all existing .Net codebase, because my solution does not actually change anything, except for adding sweet flavor to the code 😅.
Just could be handy for consumers who write 100+ statements inside one if clause, I know few of those myself 😁.

[FaustVX]

This should be

public static bool IsNullOrEmpty([NotNullWhen(false)] this IEnumerable? value);

With the static and this

[FaustVX]

No, that's not how extension methods works
sharplab.io

[tvardero]

Wow, more I live, more I learn. Never thought that I could use extensions method invocations on something that is currently null 😅
(Yep, because extension method do not belong to the object they are being invoked on. They are static methods of some other class.)

However the reason I did so, is because I want it be similar to already existing string.IsNullOrEmpty(). It would be much more expected / intuitive to developers because they saw something similar already.

[FaustVX]

Yes, but all IEnumerable methods are static

[bartonjs]

There's a guideline that says not to allow null to work in (public) extension methods, even though the language/runtime allows it; because it definitely confuses people when thingIKnowIsNull.Something() doesn't throw. So an Enumerable.IsNullOrEmpty, if added, would be a normal/non-extension method.

[FaustVX]

Ok, it makes sense