示例：

// Initial list source of values
    // This MUST be an observable collection
    private readonly ObservableCollection<string> lst2Source
        = new ObservableCollection<string>() { "1", "2" };

    // Immutable list of adding values
    private readonly ReadOnlyCollection<string> topLevel
        = Array.AsReadOnly("000 100 200 300 400 500 600 700 800 900".Split());

    public SomeWindow()
    {
        InitializeComponent();

        // Source is assigned once after XAML initialization
        lst2.ItemsSource = lst2Source;
    }

    private readonly Random random = new Random();
    private void AddRandom(int count)
    {
        topLevel
            .OrderBy(_ => random.Next())
            .Take(count)
            .ToList()
            .ForEach(level => lst2Source.Add(level)); // Elements are added not to the UI element, but to the value source
    }

它只会在我的列表框中打印1和2
我不能lst2.items.clear（）;
“1”和“2”是示例的初始列表值。如果不需要它们，请删除它们。
若要加入随机元素，请呼叫AddRandom（...）方法。
若要清除集合，请呼叫lst2Source.Clear（）。