Convert IList to array in C#

Question

I want to convert IList to array: Please see my code:

IList list = new ArrayList();
list.Add(1);
Array array = new Array[list.Count];
list.CopyTo(array, 0);

Why I get System.InvalidCastException : At least one element in the source array could not be cast down to the destination array type ? How that can be resolved assuming I can not use ArrayList as type for list variable ?

Update 1: I use .NET 1.1. So I can not use Generics, Linq and so on. I just want to receive result for the most common case - integer was given as example, I need this code works for all types so I use Array here (maybe I am wrong about using Array but I need, once again, common case).

Answer 1

You're creating an array of Array values . 1 is an int , not an Array . You should have:

IList list = new ArrayList();
list.Add(1);
Array array = new int[list.Count];
list.CopyTo(array, 0);

or, ideally, don't use the non-generic types to start with... use List instead of ArrayList , IList<T> instead of IList etc.

EDIT: Note that the third line could easily be:

Array array = new object[list.Count];

instead.

Answer 2

您可以使用Cast和ToArray：

Array array = list.Cast<int>().ToArray();

Answer 3

I'm surprised that

 Array array = new Array[list.Count];

even compiles but it does not do what you want it to. Use

 object[] array = new object[list.Count];

And, standard remark: if you can use C#3 or later, avoid ArrayList as much as possible. You'll probably be happier with a List<int>

Answer 4

可能最紧凑的解决方案是：

Enumerable.Range(0, list.Count).Select(i => list[i]).ToArray();