Winforms, databinding, Listbox and textbox

One of the easiest way, I guess, would be to use a BindingSource, setting it as the ListBox.DataSource property to your BindingSource on design.

1. Drop a BindingSource on your form;
2. Set your ListBox.DataSource property to your BindingSource;
3. Set your ValueMember and DisplayMember properties just like you're actually doing;
4. Make your DataBinding for your TextBox control, and use your BindingSource as the source, using your MyItem.Comment property;
5. Assign your List(Of MyItem) to your Binding.DataSource property;
6. Your TextBox should follow the CurrencyManager.CurrentItem's Comment property, that is, the currently ListBox.SelectedItem.

Indeed, you would perhaps need to implement the INotifyPropertyChanged interface to make it work properly.

But if this all work perfect with the SelectValue, why don't you just use it?