强类型ArrayLists是C＃中更好的选择吗？

Question

When I program in C# , there are times when I need a strongly typed collection:

I often create a class that inherits from the ArrayList :

using System.Collections;
public class Emails: ArrayList
{
  public new Email this[int i]
  {
     get
     {
        return (Email)base[i];
     }
     set
     {
        base[i] = value;
     }
  }
}

I realize this is probably not the correct way to inherit from a collection. If I want to inherit from a strongly typed collection in C#, how should I do it, and what class should I choose to inherit from?

Answer 1

What you want is a generic , like List<T> .

public class Emails : List<Email>
{
}

This has all of the methods of ArrayList and then some, and you get type safety without having to do any extra work.

Note, however, that inheriting from List<T> can sometimes cause you more trouble than it's worth. A better idea is to implement ICollection<T> or IEnumerable<T> , and use the List<T> internally to implement the interface.

Answer 2

Forget both ArrayList and List. The "right" thing to do would be to derive from Collection and call your class something that ends in Collection.

public sealed class EmailCollection : Collection<Email>
{

}

Answer 3

If you're not stuck with .Net 1.1, you really should forget about ArrayList and use the generic List<T> instead. You get strong typing and better performances to boot.

Answer 4

In general new should be avoided for member declaration if at all possible.

As of C# 2 though you can use generics. List<email> list = new List<email>();

Answer 5

不是，这就是泛型的用途。

Answer 6

Generics seem much more appropriate. For example,

List<email> 

in this case. Why reinvent the wheel and perform worse?

Answer 7

如果您使用.net 2.0或+我将使用通用集合