Question

I have a listbox inside a custom control. I use this custom control into a form. I would like to be able to get the listbox index changed event when I am working into the form. How can I do that?

Answer 1

This can be a disadvantage of a UserControl. You have to re-publish the events and the properties of one or more of its embedded controls. Consider the alternative: if this UserControl only contains a ListBox then you are much better off simply inheriting from ListBox instead of UserControl.

Anyhoo, you’ll need to re-fire the SelectedIndexChanged event. And surely you’ll need to be able to let the client code read the currently selected item. Thus:

public partial class UserControl1 : UserControl {
    public event EventHandler SelectedIndexChanged;

    public UserControl1() {
        InitializeComponent();
    }

    private void listBox1_SelectedIndexChanged(object sender, EventArgs e) {
        EventHandler handler = SelectedIndexChanged;
        if (handler != null) handler(this, e);
    }
    public object SelectedItem {
        get { return listBox1.SelectedItem; }
    }
}