What's the use of .Any() in a C# List<>?

  • I've been discussing this with colleagues, and we couldn't figure out what the use is of .Any for any given List<>, in C#.

    You can check the validity of an element in the array like the following statement:

    if (MyList.Any()){ ...}  //Returns true or false

    Which is exactly the same as

    if (MyList.Count() != 0) { ... }

    and is much more common, readable and clear about the intent of the if statement.

    In the end, we were stuck with this thought:

    .Any() can be used, will work just as well, but is less clear about the intent of the programmer, and it that case it should not be used.

    But we feel like this can't be right; we must be missing something.

    Are we?

    in what way is any less clear on intent?

    I challenge your claim that `Any()` is less clear: `Any()` seems more clear to me, especially with a lambda-condition. Translating code to English in my head, `if(MyList.Count(o => o > 10) > 0)` becomes _"Is the number of items greater than 10 more than 0?"_ whereas `if(MyList.Any(o => o > 10))` becomes _"Are there any items greater than 10?"_

    In some regards, these functions are not well-named. In C++, it would have been `if (!list.empty())`, which seems more related to a list being empty or not. While I am not usually into negating things, `list not empty` is clearer to me than `list any`. Surely, if you insert a `list _has_ any`, it's clearer. But then, Any also has other meanings, e.g. "any true", and you have to put it in mentally, already knowing what "Any" does.

    they are not well-named because they are trying to mimic SQL. (select instead of map, aggregate instead of fold, where instead of filter, etc.); in Haskell this is a lot better.

    @SargeBorsch - only if you prefer Heskel/functional naming, which most people don't.

    @BlueRaja-DannyPflughoeft i agree. I think any is more clear since it eliminates a what could be considered a magic number.

    @SargeBorsch any is the same in haskell?

    @SargeBorsch: The SQL parallel to `Any` is `Exists`. The Linq name is probably more inspired by Haskell and Python which also have any/all functions.

    @phresnel: Empty() works when there is no predicate but reads really strange when a predicate is supplied. Any() works in both cases and have a nice symmetry with All(), and the Any()/All() pair have precedence in other languages.

    @JacquesB: Personally, I associate any/none/all with checking for a condition _on_ a list, but not with the meaning of "has any". Probably because there is no symmetry between "list.empty"=="list *is* empty", and "list.any"=="list *has* any". Whereas upon a list, it reads "if any true in list", "if none true in list", "if all true in list". I guess it's that symmetry that makes it less intuitive to me. Personally, while I find it uglier, but I think I would prefer if they'd just stick to "list.hasXXX", "list.isXXX" naming convention, looks less leet, but is less ambiguous.

    With 3 more years of experience behind me (it was my second year of development back in 2015), I do not have the same point of view I had back in the day. After re-reading the question I wrote, I now completely disagree with the intent being unclear.

    Why is this not a question on stackoverflow?

    @KolobCanyon Because on stackoverflow the answer would've been one single line explaining what Any actually does, and not my actual question which is "why would you do it" and not "what does it do ?"

  • Keep in mind that Any doesn't operate on a List; it operates on an IEnumerable, which represents a concrete type that may or may not have a Count property. It's true that it's not necessarily the best thing to use on a List, but it definitely comes in handy at the end of a LINQ query. And even more useful than the standalone version is the override that takes a predicate just like Where. There's nothing built in on List that's anywhere near as convenient or expressive as the predicate-Any extension method.

    Also, if you're using Count() (the LINQ extension method for IEnumerable), rather than Count (the property on List), it can have to enumerate the entire sequence if it can't optimize this away by detecting that your underlying data type has a Count Property. If you have a long sequence, this can be a noticeable performance hit when you don't really care about what the count is, and just want to know if there are any items in the collection.

    This. Performance aside, `Any()` with a predicate is *more* expressive than comparing the override of `Enumerable.Count()` that takes a predicate with 0. :)

    I think this explains the fundamentals so clearly that explains the answer at best.

    IMHO, `Exists` is just as convenient and expressive as `Any`, with a predicate. Using `Count != 0` property on a `List` is more normal than using `Any()`. It's just personal preference. I've also gone through the effort of changing `_list_.Count()` to `_list_.Count` in my group's code. It made a noticeable difference to me.

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Content dated before 6/26/2020 9:53 AM