Question

Hey. I’ve got the following code that populates my list box

UsersListBox.DataSource = GrpList;

However, after the box is populated, the first item in the list is selected by default and the “selected index changed” event fires. How do I prevent the item from being selected right after the list box was populated, or how do I prevent the event from firing?

Thanks

Answer 1

To keep the event from firing, here are two options I have used in the past:

1. Unregister the event handler while setting the DataSource.

   UsersListBox.SelectedIndexChanged -= UsersListBox_SelectedIndexChanged;
   UsersListBox.DataSource = GrpList;
   UsersListBox.SelectedIndex = -1; // This optional line keeps the first item from being selected.
   UsersListBox.SelectedIndexChanged += UsersListBox_SelectedIndexChanged;
   

2. Create a boolean flag to ignore the event.

   private bool ignoreSelectedIndexChanged;
   private void UsersListBox_SelectedIndexChanged(object sender, EventArgs e)
   {
       if (ignoreSelectedIndexChanged) return;
       ...
   }
   ...
   ignoreSelectedIndexChanged = true;
   UsersListBox.DataSource = GrpList;
   UsersListBox.SelectedIndex = -1; // This optional line keeps the first item from being selected.
   ignoreSelectedIndexChanged = false;