WinForms data binding

Question

I am new in data binding.

I have those classes:

public class Foo : List<Bar>
{
    public string FooName { get; set; }
}

public class Bar
{
    public string BarName { get; set; }
    public string BarDesc { get; set; }
}

And I have a List<Foo>

I would like to have Foo items in ComboBox, and Bar items in ListBox. When I change selected item in ComboBox, I want ListBox to change. When I change selected item in ListBox I would like to have TextBox filled with BarDesc.

Following works only for ListBox and ComboBox:

comboBox1.DataSource = foos;
comboBox1.DisplayMember = "FooName";
listBox1.DataBindings.Add("DataSource", foos, "");
listBox1.DisplayMember = "BarName";

I don't now how to bind selected Bar in ListBox to TextBox.Text property. Maybe added binding for listBox1 is not a good idea.

Maybe I should do something like that:

((CurrencyManager)listBox1.BindingContext[foos]).CurrentChanged += new EventHandler((o, a) =>
{
    textBox1.DataBindings.Clear();
    textBox1.DataBindings.Add("Text", listBox1.DataSource, "BarDesc");
});

How can I resolve my problem?

Answer 1

Use BindingSource for all your complex data binding needs:

// bind to List<Foo>
BindingSource comboBoxBindingSource = new BindingSource();
comboBoxBindingSource.DataSource = foos;
// use this binding source in comboBox1
// for display use FooName
comboBox1.DataSource = comboBoxBindingSource;
comboBox1.DisplayMember = "FooName";

// bind to comboBox1's SelectedValue
// it will point to the Foo selected in combobox
BindingSource listBoxBindingSource = new BindingSource();
listBoxBindingSource.DataSource = comboBox1;
listBoxBindingSource.DataMember = "SelectedValue";
// use this binding source in listBox1
// for display use BarName
listBox1.DataSource = listBoxBindingSource;
listBox1.DisplayMember = "BarName";

// bind to comboBox'1s SelectedValue (reusing listBoxBindingSource)
// and set Text to value of BarDesc
textBox1.DataBindings.Add("Text", listBoxBindingSource, "BarDesc");

Answer 2

You should probably set the ValueMember on the combo and the list box. You might need to also handle bindingSource.CurrentChanged and rebind the listbox to the currently selected list.

Answer 3

To make all this work, I had to add the Items property to the Foo class. This is the "link/relationship" between the two binding sources.

public partial class Form1 : Form {
    public class Foo : List<Bar> {
        public string FooName { get; set; }
        public Foo(string name) { this.FooName = name; }
        public List<Bar> Items { get { return this; } }
    }
    public class Bar {
        public string BarName { get; set; }
        public string BarDesc { get; set; }
        public Bar(string name, string desc) {
            this.BarName = name;
            this.BarDesc = desc;
        }
    }
    public Form1() {

        InitializeComponent();

        List<Foo> foos = new List<Foo>();

        Foo a = new Foo("letters");
        a.Add(new Bar("a", "aaa"));
        a.Add(new Bar("b", "bbb"));
        foos.Add(a);

        Foo b = new Foo("digits");
        b.Add(new Bar("1", "111"));
        b.Add(new Bar("2", "222"));
        b.Add(new Bar("3", "333"));
        foos.Add(b);

        //Simple Related Object List Binding
        //http://blogs.msdn.com/bethmassi/archive/2007/04/21/simple-related-object-list-binding.aspx

        BindingSource comboBoxBindingSource = new BindingSource();
        BindingSource listBoxBindingSource = new BindingSource();

        comboBoxBindingSource.DataSource = foos;
        listBoxBindingSource.DataSource = comboBoxBindingSource;
        listBoxBindingSource.DataMember = "Items";

        comboBox1.DataSource = comboBoxBindingSource;
        comboBox1.DisplayMember = "FooName";

        listBox1.DataSource = listBoxBindingSource;
        listBox1.DisplayMember = "BarName";

        textBox1.DataBindings.Add("Text", listBoxBindingSource, "BarDesc");

    }
}