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Data binding to ComboBoxes

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My problem here is, that I don't know how to bind SelectedIndex of ComboBox. I already achieved ItemSource binding. Works great. But now I wish to bind SelectedIndex to another object using some kind of converter. Actually I am working on filtering trough results(sending request to server...).

Here is xaml example of one specific ComboBox

<ComboBox Grid.Row="1" x:Name="showStatus_picker" Style="{StaticResource basicDropDown}" Width="400" ItemsSource="{Binding}" > <ComboBox.ItemTemplate> <DataTemplate> <TextBlock Text="{Binding Value}" /> </DataTemplate> </ComboBox.ItemTemplate> </ComboBox>

C# code

public class filterDropValues
{
public filterDropValues(string key, string value)
{
this.Key = key;
this.Value = value;
}

public string Key { get; private set; }
public string Value { get; private set; }
}
dropDownList[0].Add(new filterDropValues("ALL", loader.GetString("filterALL")));
dropDownList[0].Add(new filterDropValues("Mine", loader.GetString("filterMine")));
dropDownList[0].Add(new filterDropValues("val1", loader.GetString("val1")));
dropDownList[0].Add(new filterDropValues("val2", loader.GetString("val2")));
dropDownList[0].Add(new filterDropValues("val3", loader.GetString("val3")));
showStatus_picker.DataContext = dropDownList[0];

All that code works just fine. But as I mentioned before, I need binding for SelectedIndex. Two way direction. So when I change SelectedIndex, object value will also changed to selected value(trough converter I suppose).

I don't wish total solution, only push me to the right direction. I will write converter and everything on my own, I only need an idea, how to bind SelectedIndex in xaml.

Actually I decide to ask you guys here, because I really couldn't find the solution for past few days. I see only one solution here, but it is really ugly...when user interact with any control on my filter I will have to manually check if value is changed for each and every control...

Sorry for long post, I hope, it was understandable and sorry for my poor English. Thanks
- Edited by Klemzy2013 Friday, December 13, 2013 10:09 PM
Friday, December 13, 2013 10:06 PM

Answers

Hi,

You can register a dependency property in a class. Set the combobox DataContext to the calss object. Then bind the combobox selectvalue to the dependency property using a converter. There is a sample you can refer to:

XAML:

 <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <Grid.Resources>
            <local:ToStringConverter x:Key="Converter1"/>
        </Grid.Resources>
        <ComboBox Margin="324,233,403,363" x:Name="showStatus_picker"  ItemsSource="{Binding dropDownList }" SelectedValue="{Binding Index, Converter={StaticResource Converter1},Mode=TwoWay}" >
            
        </ComboBox>
        <Button Content="Button" HorizontalAlignment="Left" Margin="1172,622,0,0" VerticalAlignment="Top" Click="Button_Click"/>
    </Grid>

Code-behind:

 public sealed partial class MainPage : Page
    {
       public  static TestViewModel testviewmodel = new TestViewModel();
        public MainPage()
        {
            this.InitializeComponent();
            showStatus_picker.DataContext = testviewmodel;

        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            testviewmodel.Index = 1;
        }
    }
    
    public class TestViewModel : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        private ObservableCollection<string> _dropDownList = new ObservableCollection<string> { "filterALL", "filterMine", "val1", "val2" };
        public ObservableCollection<string> dropDownList { get { return _dropDownList; } }
        private int index;

        public int Index
        {

            get { return this.index; }

            set
            {

                if (this.index != value)
                {

                    this.index = value;

                    if (this.PropertyChanged != null)

                        this.PropertyChanged(this, new PropertyChangedEventArgs("Index"));

                }

            }

        }

    }
   

    public class ToStringConverter : IValueConverter
    {

        #region IValueConverter Members

        public object Convert(object value, Type targetType,
            object parameter, string language)
        {

           
            string selectvalue;
            int index =(int)value;
            selectvalue = MainPage.testviewmodel.dropDownList[index];
            return selectvalue;
        }

        public object ConvertBack(object value, Type targetType,
            object parameter, string language)
        {
            throw new NotImplementedException();
        }

        #endregion
    }

When click the button the Index would change so that the Combobox SelectValue also would change.

Best Wishes!

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Edited by Anne Jing Monday, December 16, 2013 8:15 AM edit
Marked as answer by Klemzy2013 Monday, December 16, 2013 8:39 AM

Monday, December 16, 2013 8:14 AM

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Data binding to ComboBoxes

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