Create an instance of Random class somewhere. Note that it's pretty important not to create a new instance each time you need a random number. You should reuse the old instance to achieve uniformity in the generated numbers. You can have a static field somewhere (be careful about thread safety issues): static Random rnd = new Random(); Ask the Random instance to give you a random number with the maximum of the number of items in the ArrayList: int r = rnd.Next(list.Count); Display the string: MessageBox.Show((string)list[r]);

我需要更多的项目，而不仅仅是一个。所以，我写了这个:

public static TList GetSelectedRandom<TList>(this TList list, int count)
       where TList : IList, new()
{
    var r = new Random();
    var rList = new TList();
    while (count > 0 && list.Count > 0)
    {
        var n = r.Next(0, list.Count);
        var e = list[n];
        rList.Add(e);
        list.RemoveAt(n);
        count--;
    }

    return rList;
}

有了这个，你可以像这样随机获取你想要的元素:

var _allItems = new List<TModel>()
{
    // ...
    // ...
    // ...
}

var randomItemList = _allItems.GetSelectedRandom(10); 

ArrayList ar = new ArrayList();
        ar.Add(1);
        ar.Add(5);
        ar.Add(25);
        ar.Add(37);
        ar.Add(6);
        ar.Add(11);
        ar.Add(35);
        Random r = new Random();
        int index = r.Next(0,ar.Count-1);
        MessageBox.Show(ar[index].ToString());

Create an instance of Random class somewhere. Note that it's pretty important not to create a new instance each time you need a random number. You should reuse the old instance to achieve uniformity in the generated numbers. You can have a static field somewhere (be careful about thread safety issues): static Random rnd = new Random(); Ask the Random instance to give you a random number with the maximum of the number of items in the ArrayList: int r = rnd.Next(list.Count); Display the string: MessageBox.Show((string)list[r]);

创建一个随机实例:

Random rnd = new Random();

获取一个随机字符串:

string s = arraylist[rnd.Next(arraylist.Count)];

记住，如果你经常这样做，你应该重用随机对象。将它作为类中的静态字段，这样它只初始化一次，然后访问它。

为什么不:

public static T GetRandom<T>(this IEnumerable<T> list)
{
   return list.ElementAt(new Random(DateTime.Now.Millisecond).Next(list.Count()));
}