WPF Binding objects defined in codebehind

Question

I have some object that is instantiated in code behind, for instance, the XAML is called window.xaml and within the window.xaml.cs

protected Dictionary<string, myClass> myDictionary;

How can I bind this object to, for example, a list view, using only XAML markups?

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Edit v2

(This is exactly I have in my test code):

<Window x:Class="QuizBee.Host.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="{Binding windowname}" Height="300" Width="300"
    DataContext="{Binding RelativeSource={RelativeSource Self}}">
    <Grid>

    </Grid>
</Window>

And in codebehind

public partial class Window1 : Window
{
    public const string windowname = "ABCDEFG";

    public Window1()
    {
        InitializeComponent();
    }
}

Suppose the title should become "ABCDEFG" right? but it ends up showing nothing.

Answer 1

In your code behind, set the window's DataContext to the dictionary. In your XAML, you can write:

<ListView ItemsSource="{Binding}" />

This will bind the ListView to the dictionary.

For more complex scenarios, this would be a subset of techniques behind the MVVM pattern.

Answer 2

One way would be to create an ObservableCollection (System.Collections.ObjectModel) and have your dictionary data in there. Then you should be able to bind the ObservableCollection to your ListBox.

In your XAML you should have something like this:

<ListBox ItemsSource="{Binding Path=Name_of_your_ObservableCollection" />

Answer 3

You can set the DataContext for your control, form, etc. like so:

DataContext="{Binding RelativeSource={RelativeSource Self}}"

Clarification:

The data context being set to the value above should be done at whatever element "owns" the code behind -- so for a Window, you should set it in the Window declaration.

I have your example working with this code:

<Window x:Class="MyClass"
  Title="{Binding windowname}"
  DataContext="{Binding RelativeSource={RelativeSource Self}}"
  Height="470" Width="626">

The DataContext set at this level then is inherited by any element in the window (unless you explicitly change it for a child element), so after setting the DataContext for the Window you should be able to just do straight binding to CodeBehind properties from any control on the window.

Answer 4

Define a converter:

public class RowIndexConverter : IValueConverter
{
    public object Convert( object value, Type targetType,
                           object parameter, CultureInfo culture )
    {
        var row = (IDictionary<string, object>) value;
        var key = (string) parameter;
        return row.Keys.Contains( key ) ? row[ key ] : null;
    }

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

Bind to a custom definition of a Dictionary. There's lot of overrides that I've omitted, but the indexer is the important one, because it emits the property changed event when the value is changed. This is required for source to target binding.

public class BindableRow : INotifyPropertyChanged, IDictionary<string, object>
{
    private Dictionary<string, object> _data = new Dictionary<string, object>( );

    public object Dummy   // Provides a dummy property for the column to bind to
    {
        get
        {
            return this;
        }
        set
        {
            var o = value;
        }
    }


    public object this[ string index ]
    {
        get
        {
            return _data[ index ];
        }
        set
        {
            _data[ index ] = value;
            InvokePropertyChanged( new PropertyChangedEventArgs( "Dummy" ) ); // Trigger update
        }
    }


}

In your .xaml file use this converter. First reference it:

<UserControl.Resources>
    <ViewModelHelpers:RowIndexConverter x:Key="RowIndexConverter"/>
</UserControl.Resources>

Then, for instance, if your dictionary has an entry where the key is "Name", then to bind to it: use

<TextBlock  Text="{Binding Dummy, Converter={StaticResource RowIndexConverter}, ConverterParameter=Name}">

Answer 5

Make your property "windowname" a DependencyProperty and keep the remaining same.