Winforms, databinding, Listbox and textbox

Question

I have a ListBox ( MyListBox ) on my screen, and a Textbox ( MyTextBox ).

The ListBox is filled with a List(Of T), which are all custom items.

Now I try to do this:

The ListBox' datasource is the List(Of T).

Now when an Item changes I want the textbox to be updated to a particular property of the selected item in my ListBox.

In code this means:

Me.MyListBox.DisplayMember = "SelectionName"
Me.MyListBox.ValueMember = "Id"

MyTextbox.DataBindings.Add(New Binding("Text", Me._listOfItems, "SelectedItem.Comment", True, DataSourceUpdateMode.OnPropertyChanged))

Me.MyListBox.DataSource = Me._listOfItems

this does not work. But when I bind to SelectedValue instead of SelectedItem it works perfectly.

The _listOfItems is declared as this:

Dim _listOfItems As List(Of MyItem) = New List(Of MyItem)()

Where MyItem is this:

public class MyItem
{
    public string SelectionName { get; set; }
    public int Id { get; set; }
    public string Comment { get; set; }
}

I tried overriding the ToString() in MyItem so that it would use that. But that doesn't work either.

Anybody care to give it a try?

Answer 1

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?

Answer 2

The code below shows how I am doing it. I first set my ListBox DataSource to a class with a collection of BindingList. The class implements IBindingList. I have two TextBoxes I want to bind the SelectedItem to. The code below is how I am doing it:

lbControl.DataSource = SharepointTestBusinessLayer.Control.ListAll();
lbControl.DisplayMember = "ControlName";
lbControl.SelectedIndex = 0;
scTextBoxControlID.DataBindings.Add("Text", this.lbControl.DataSource, "ControlID");
scTextBoxControlName.DataBindings.Add("Text", this.lbControl.DataSource, "ControlName");