Winforms ListBox control Items property empty in DataSourceChanged event handler

Question

Does anyone know what event to hook into to know when data binding is complete on a ListBox control after setting its DataSource?

Hooking into DataSourceChanged doesn't do the trick as the Items collection is still empty on the control when this event is fired.

The answer to my similar question might do the trick for you; see http://stackoverflow.com/questions/34421735/how-can-i-immediately-reactively-determine-if-any-checkedboxlistitem-has-been-se — B. Clay Shannon-B. Crow Raven, Dec 22 '15 at 18:16

score 1 · Answer 1 · answered Dec 22 '15 at 18:25

The easy way is to just use the DataSource collection instead:

void listBox1_DataSourceChanged(object sender, EventArgs e) {
  var count = ((ICollection)listBox1.DataSource).Count;
}

Cast the DataSource appropriately.

Otherwise, you can use BeginInvoke to get the update after the DataSourceChanged event has run its course:

void listBox1_DataSourceChanged(object sender, EventArgs e) {
  this.BeginInvoke(new Action(() => {
    var count = listBox1.Items.Count;
  }));
}

score 1 · Answer 2 · answered Dec 24 '15 at 08:03

1

Thanks guys. I actually decompiled the ListBox code using Resharper and found that the DisplayMemberChanged event did the trick for me so I used that. Thanks for the suggestions though!

answered Dec 24 '15 at 08:03

BigBytes

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score 0 · Answer 3 · answered Dec 22 '15 at 20:21

Does anyone know what event to hook into to know when data binding is complete on a ListBox control after setting its DataSource?

There is no such event. But you can create your own ListBox subclass and expose such event like this

public class MyListBox : ListBox
{
    public event EventHandler DataSourceApplied;

    protected override void OnDataSourceChanged(EventArgs e)
    {
        base.OnDataSourceChanged(e);
        var handler = DataSourceApplied;
        if (handler != null) handler(this, EventArgs.Empty);
    }
}

Winforms ListBox control Items property empty in DataSourceChanged event handler

3 Answers3