List<T> Any or Count? [duplicate]

This question already has answers here: Which method performs better: .Any() vs .Count() > 0? (11 answers) 开发者_运维知识库 Closed 3 years ago.

When I want to do something with a list I first check it if is not null or contains no elements (not to blow a foreach) and I usually use list.Any() but what is the best option - to use list.Count > 0 , or to use list.Any()?

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• Use Count if you're using a List, since it knows its size.
• Use Length for an Array
• If you just have an IEnumerable I would use .Any() over .Count() as it will be faster since it stops after checking one item.

Also check out this question: Which method performs better: .Any() vs .Count() > 0?

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I use list.Count > 0 just because it doesn't depend on the LINQ methods and so works on C# 2.0.

I personally avoid LINQ like the plague (because of its slow speed), and there's no reason to use extension methods here at all anyway.

However, a better solution would probably be to make your own version of Any that would take in a null reference, and return true if it's a collection with elements. That would save you the null check.

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.Any() is generally better to use than .Count() > 0. The reason for this is that if the items you are iterating over is not an ICollection then it will have to iterate the whole list to get the count.

But if the items is an ICollection (which a List<T> is) then it is just as fast or in some cases faster to use Count() (Any() iterates once regardless of underlying type in MS .Net but Mono tries to optimize this to Count > 0 when the underlying items is an ICollection)

A great tool is Reflector, the .Net source code and the Mono source code which allows you to see how things are implemented.

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If you are using the Entity Framework and have a huge table with many records Any() will be much faster. I remember one time I wanted to check to see if a table was empty and it had millions of rows. It took 20-30 seconds for Count() > 0 to complete. It was instant with Any().

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Any() can be a performance enhancement because it may not have to iterate the collection to get the number of things. It just has to hit one of them. Or, for, say, LINQ-to-Entities, the generated SQL will be IF EXISTS(...) rather than SELECT COUNT ... or even SELECT * ....