Databinding issue with ComboBox

Question

When binding data to combobox, 3 items need to be set:

<ComboBox  ItemsSource="{Binding MyList}" SelectedItem="{Binding MyItem}"  DisplayMemberPath="MyName"   />

Say ItemSource is list of Country

I set itemsource to right source firstly, it is fine. Then I set selectedItem to specific Country object, but it's not working.

Looks like all need to be set when ItemSource is setting.

How to resolve this problem?

Answer 1

UPDATE WITH WORKING CODE

Make sure you enable two-way binding on the SelectedItem.

<ComboBox ItemsSource="{Binding Path=Countries, Mode=OneWay}" SelectedItem="{Binding Path=SelectedCountry, Mode=TwoWay}" Height="23" HorizontalAlignment="Left" Margin="12,28,0,0" Name="comboBox1" VerticalAlignment="Top" Width="267" />

Here is what your context will look like:

public partial class MainPage : UserControl, INotifyPropertyChanged
{
    public MainPage() 
    { 
        InitializeComponent();
        this.Countries = new ObservableCollection<string> { "USA", "CAN" };
        this.DataContext = this;
    }

    public event PropertyChangedEventHandler PropertyChanged;
    public ObservableCollection<string> Countries { get; set; }

    private string _selectedCountry = null;
    public string SelectedCountry
    {
        get { return _selectedCountry; }
        set
        {
            _selectedCountry = value;
            if( this.PropertyChanged != null )
                this.PropertyChanged( this, new PropertyChangedEventArgs( "SelectedCountry" ) );
        }
    }

    private void button1_Click( object sender, RoutedEventArgs e )
    {
        MessageBox.Show( "Selected Country: " + this.SelectedCountry );
    }

}