Array.Length vs Array.Count [duplicate]

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Possible Duplicate:
count vs length vs size in a collection

In .NET, pretty much all collections have the .Count property.

Sometimes I wonder if it would be better to have it on Array as well, directly though, not through ICollection.

It's just something you make an exception in your mind only for arrays.

So is it better to be "more correct" or "more uniform" in this case?

Side effects from using similar code in .NET languages should also be considered. In C# using Length incorrectly will throw an error because it either isn't available or it returned the wrong type of data. In PowerShell, Count and Length produce the same result for arrays, but collection objects don't return the expected result for Length. For example, ([ordered]@{'a' = 0; 'bc' = 0;'def' = 0;}).Keys.Length returns 1,2,3 and not 3. This is because Length returns a list of Length properties for each key, which is the length of each string. — Dave F
– Dave F, Commented Dec 24, 2021 at 17:33

to StackOverflow · Accepted Answer · 2009-10-05 11:54:02Z

9

In many cases where a one-dimensional array is used, it's essentially being used as a fixed-size list.

Personally I will often declare an array as IList<T>, and use the Count property rather than Length:

IList<string> strings = new string[] { ...};

Another useful member of IList<T> that does not exist in Array is the Contains() method.

edited Oct 5, 2009 at 11:54

answered Oct 2, 2009 at 6:40

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elder_george · Accepted Answer · 2009-10-02 11:42:13Z

3

If you're using C# 3.0, you may use Enumerable.Count() extension method that works on all IEnumerable implementations, including lists, arrays and dictionaries.

It causes some overhead, but it's usually tolerable.

answered Oct 2, 2009 at 11:42

elder_george

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John von No Man Over a year ago

If there's any chance at all, though, that you're working on a critical code path that could be executed a lot of times, you need to understand what the Count() method is doing. It can get hairy if you're running some kind of LINQ query and you want to count how many items are in the database -- Count() will actually pull down all the data and enumerate through every element. Very inefficient for large data sets.

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