ListBox1_SelectedIndexChanged 未触发

Question

I'm trying to make a windows forms app for the first time. I have two list boxes. The first one is being populated from a .txt-file when starting the program:

 public Form1()
        {
                InitializeComponent();
                string[] lines = File.ReadAllLines("C:\\Users\\Mitarbeiter.txt");
                ListBox listBoxMitarbeiter = new ListBox();                           
                listBoxMitarbeiter.Size = new System.Drawing.Size(200, 350);
                listBoxMitarbeiter.Location = new System.Drawing.Point(30, 100);
                this.Controls.Add(listBoxMitarbeiter);
                listBoxMitarbeiter.SelectionMode = SelectionMode.MultiExtended;
                listBoxMitarbeiter.BeginUpdate();
                int c = 0;
                foreach (string line in lines)
                {
                    listBoxMitarbeiter.Items.Insert(c, line);
                    c++;
                }
                listBoxMitarbeiter.EndUpdate();
         }

Now I want the second list box to be created and populated when a item/index is selected in the first one:

private void listBoxMitarbeiter_SelectedIndexChanged(object sender, System.EventArgs e)
        {               
                ListBox listBox2 = new ListBox();
                listBox2.Size = new System.Drawing.Size(200, 350);
                listBox2.Location = new System.Drawing.Point(200, 100);
                this.Controls.Add(listBox2);
                listBox2.SelectionMode = SelectionMode.MultiExtended;
                listBox2.BeginUpdate();
                listBox2.Items.Insert(2,"it works");               
                listBox2.EndUpdate();
        }

I've read that you are supposed to somehow link the event with the listbox. How? Or is it something else entirely. Please help.

Answer 1

You need to add an event handler to the listbox:

listBoxMitarbeiter.SelectedIndexChanged +=
    new EventHandler(listBoxMitarbeiter_SelectedIndexChanged);

This way, the listBoxMitarbeiter_SelectedIndexChanged() method will be called on each SelectedIndexChanged event.