[英]How to convert an ArrayList to a strongly typed generic list without using a foreach?
See the code sample below. 请参阅下面的代码示例。 I need the
ArrayList
to be a generic List. 我需要
ArrayList
作为通用List。 I don't want to use foreach
. 我不想使用
foreach
。
ArrayList arrayList = GetArrayListOfInts();
List<int> intList = new List<int>();
//Can this foreach be condensed into one line?
foreach (int number in arrayList)
{
intList.Add(number);
}
return intList;
Try the following 请尝试以下方法
var list = arrayList.Cast<int>().ToList();
This will only work though using the C# 3.5 compiler because it takes advantage of certain extension methods defined in the 3.5 framework. 这只能使用C#3.5编译器,因为它利用了3.5框架中定义的某些扩展方法。
这是低效的(它不必要地创建一个中间数组)但是简洁并且可以在.NET 2.0上运行:
List<int> newList = new List<int>(arrayList.ToArray(typeof(int)));
How about using an extension method? 使用扩展方法怎么样?
From http://www.dotnetperls.com/convert-arraylist-list : 来自http://www.dotnetperls.com/convert-arraylist-list :
using System;
using System.Collections;
using System.Collections.Generic;
static class Extensions
{
/// <summary>
/// Convert ArrayList to List.
/// </summary>
public static List<T> ToList<T>(this ArrayList arrayList)
{
List<T> list = new List<T>(arrayList.Count);
foreach (T instance in arrayList)
{
list.Add(instance);
}
return list;
}
}
In .Net standard 2 using Cast<T>
is better way: 在.Net标准2中使用
Cast<T>
是更好的方法:
ArrayList al = new ArrayList();
al.AddRange(new[]{"Micheal", "Jack", "Sarah"});
List<int> list = al.Cast<int>().ToList();
Cast
andToList
are extension methods in theSystem.Linq.Enumerable
class.Cast
和ToList
是System.Linq.Enumerable
类中的扩展方法。
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