小编Shm*_*ola的帖子

对于ListBox(选择模式设置为One),我希望跟踪是否选择了所选项目.为此,我订阅了一个方法到SelectedIndexChanged并检查SelectedIndex是否为-1.但是,我注意到在调用Items.Clear()之后事件不会触发,即使SelectedIndex更改为-1(如果它还不是-1).

为什么不开火？我知道我可以通过在清除列表之前为SelectedIndex分配-1来解决这个问题.但有更好的方法吗？

这是一个复制它的简单代码:

using System;
using System.Windows.Forms;

namespace ns
{
    class Program
    {
        static ListBox lst = new ListBox();

        public static void Main()
        {
            lst.SelectedIndexChanged += new EventHandler(lst_SelectedIndexChanged);

            lst.Items.Add(1);

            Console.WriteLine("Setting selected index to 0...");
            lst.SelectedIndex = 0; //event fire here

            Console.WriteLine("(Selected Index == {0})", lst.SelectedIndex);

            Console.WriteLine("Clearing  all items...");
            lst.Items.Clear(); //event *should* fire here?!

            //proof that the selected index has changed
            Console.WriteLine("(Selected Index == {0})", lst.SelectedIndex);
        }

        static void lst_SelectedIndexChanged(object sender, EventArgs e)
        {
            Console.WriteLine("[!] Selected Index Changed:{0}", lst.SelectedIndex);
        }
    } …