Setting ComboBox DataSource to an enum and binding SelectedValue

Question

I am kinda desperate, because yesterday it was working but today this is not working anymore, let me explain, what I am trying to do:

I want to set the DataSource of a ComboBox to all enum values in a specific enum. Just like that:

cmbType.DataSource = m_addViewPresenter.Types;

where Types is a BindingList and is being initialised like that:

public BindingList<MyEnum> Types
{
    get { return m_types; }
    set
    {
        m_types = value;
        OnPropertyChanged();
    }
}

[ImportingConstructor]
public AddViewPresenter()
{
    Types = new BindingList<MyEnum>(
              Enum.GetValues(typeof(MyEnum))
                         .Cast<MyEnum>().ToList());
}

Further more, I want to bind the current item selected to a property. Since ComboBox.SelectedItem doesn't fire a INotifyProperty-event, I am using ComboBox.SelectedValue.

cmbType.Bind(m_addViewPresenter, c => c.SelectedValue, m => m.SelectedValue);

public static void Bind<TComponent, T>(
    this TComponent component, T value,
    Expression<Func<TComponent, object>> controlProperty, 
    Expression<Func<T, object>> modelProperty)
    where TComponent : IBindableComponent
    where T : INotifyPropertyChanged
{
    var controlPropertyName = PropertyNameResolver.GetPropertyName(controlProperty);
    var modelPropertyName = PropertyNameResolver.GetPropertyName(modelProperty);
    component.DataBindings.Add(new Binding(controlPropertyName, value, modelPropertyName, false, DataSourceUpdateMode.OnPropertyChanged));
}

It worked fine yesterday, but something messed things up and today I am only getting an InvalidOperationException:

Cannot set the SelectedValue in a ListControl with an empty ValueMember.

I know it's digging in the dark, but can anyone brainstorm with me and find out, what's the problem? Thanks in advance!

Looks like binding to ComboBox.SelectedValue requires setting 'ComboBox.ValueMember` — Ivan Stoev
You should really bind to ComboBox.SelectedItem, I don't know why do you think it will not fire property change notification, I think it does. — Ivan Stoev
I tried it with cmbType.Bind(m_addViewPresenter, c => c.SelectedValue, m => m.SelectedValue);, but it wasnt going into the setter. :/ — Jannik
@Jannik To use data binding to SelectedValue, use another class that contains a property as DisplayMember and a property as ValueMember and shape your enum values to a List<ThatClass> as DataSourec, or simplye use your enum values as data source and bind to SelectedItem as mentioned by Ivan too. — Reza Aghaei
Like I told you, binding SelectedItem is not going into the setter of SelectedValue, it is not working. — Jannik

Reza Aghaei Reza Aghaei · Accepted Answer · 2015-10-07T17:07:15

Option 1

To use SelectedValue for data binding, Create a calss DataItem:

public class DataItem
{
    public MyEnum Value { get; set; }
    public string Text { get; set; }
}

Then use this code for data binding:

this.comboBox1.DataSource = Enum.GetValues(typeof(MyEnum)).Cast<MyEnum>()
                                .Select(x => new DataItem() { Value = x, Text = x.ToString() })
                                .ToList();
this.comboBox1.ValueMember = "Value";
this.comboBox1.DisplayMember = "Text";

this.comboBox1.DataBindings.Add(
    new Binding("SelectedValue", yourObjectToBind, "PropertyOfYourObject"));

You can make generic DataItem<T> containing public T Value { get; set; } to make it more reusable in your project.

Option 2

To Use SelectedItem for data binding:

this.comboBox1.DataSource = Enum.GetValues(typeof(MyEnum));
this.comboBox1.DataBindings.Add(
    new Binding("SelectedItem", yourObjectToBind, "PropertyOfYourObject"));

Option 3

To use SelectedValue for data binding as another option suggested by Ivan Stoev, you can perform data to binding this way:

this.comboBox1.DataSource = Enum.GetValues(typeof(MyEnum));
this.comboBox1.DataBindings.Add(
    new Binding("SelectedValue", yourObjectToBind, "PropertyOfYourObject",
                true,  DataSourceUpdateMode.OnPropertyChanged));

Edit by Jannik:

The basic generic approach of option 1 would look like this:

public class ComboBoxItemWrapper<T>
{
    public T Value { get; set; }
    public string Text { get; set; }
}

Setting ComboBox DataSource to an enum and binding SelectedValue

2 Answers