what is different between this propery in arraylist ?

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ArrayList alist = new ArrayList();
alist.Add(0);
Console.WriteLine(alist.Count);
Console.WriteLine(alist.Capacity);

what is different between this two property Capacity and count ?

Posted 21-Feb-13 12:19pm

Anderso0on

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Sergey Alexandrovich Kryukov · Answer 1 · 2013-02-21T12:31:00

Solution 1 would be correct if it explained Capacity. It does not mean that you cannot add more items then Capacity. You can. But all you need is to read the documentation:

MSDN tells us:
Capacity is always greater than or equal to Count. If Count exceeds Capacity while adding elements, the capacity is automatically increased by reallocating the internal array before copying the old elements and adding the new elements.

More importantly: you should never use this list type. It is rendered obsolete as early as of the .NET v.2.0, when generics were introduces. You should always use generic collection types from System.Collections.Generic (and also specialized collections). For a list, use System.Collections.Generic.List<>:
http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx[^].

Non-generic types are much worse because they require potentially dangerous type cast. You never need them. However, these classes were not marked with [Obsolete] attribute, just because there is nothing wrong with using them in legacy code. In new development, there is absolutely no reason to use them.

—SA

DinoRondelly · Answer 2 · 2013-02-21T12:21:00

Solution 1

Capacity Gets or sets the number of elements that the ArrayList can contain.

Count Gets the number of elements actually contained in the ArrayList.

Posted 21-Feb-13 12:21pm

DinoRondelly

Comments

Sergey Alexandrovich Kryukov 21-Feb-13 18:33pm

The answer is confusing, in part of Capacity. Microsoft writes "can contain", but its the best not to compile these words, because they suggests that Count cannot be more than Capacity. This is just bad Microsoft wording, the documentation actually explains how it works. (I did not vote this time.)

Please see my answer.
—SA

DinoRondelly 21-Feb-13 18:40pm

I just did the guy the favor of googling arraylist, looking at the msdn and copying and pasting what they had there

http://msdn.microsoft.com/en-ca/library/system.collections.arraylist.aspx

gotta be worth atleast a 4, he could of just used the google his self, :)