问题
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).
回答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.
回答2:
You can use Cast and ToArray:
Array array = list.Cast<int>().ToArray();
回答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>
回答4:
probably the most compact solution is this:
Enumerable.Range(0, list.Count).Select(i => list[i]).ToArray();
来源:https://stackoverflow.com/questions/9507002/convert-ilist-to-array-in-c-sharp