How to bind DataTrigger to an Interface property

I have 4 class which implement my custom ICalendarItem Interface. That interface has a property called 'Jours'.

ObservableCollection<KeyValuePair<DateTime, DateTime>> Jours;

My class override that property like this :

public override ObservableCollection<KeyValuePair<DateTime, DateTime>> Jours {...}

When the Jours.Count goes from 0 to 1, i want to trigger an action so i tried this :

<DataTrigger Binding="{Binding Path=Jours.Count}" Value="1">

<DataTrigger Binding="{Bin开发者_JAVA技巧ding Path=(ICalendarItem)Jours.Count}" Value="1">

None of these 2 DataTrigger works.

Anyone know how to bind a DataTrigger to an Interface property?

When you want to specifically bind to a custom interface property, you need to place place the namespace, interface and property name within parenthesis. You can then reference a sub-property like Count outside of the parenthesis.

<DataTrigger Binding="{Binding Path=(local:ICalendarItem.Jours).Count}" Value="1">
...
</DataTrigger>

In my test, its work is done well. Please refer to the following code, which probably helps with you.

What this code do is, when `Jours.Count' equals to "3", the Window background gets red color. XAML:

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <Style TargetType="Grid">
            <Style.Triggers>
                <DataTrigger Binding="{Binding Jours.Count}" Value="3">
                    <Setter Property="Control.Background" Value="Red" />
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </Window.Resources>
    <Grid>
    </Grid>
</Window>

CodeBehind:

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        ITest test = new TestClass();
        this.DataContext = test;
    }
}

interface ITest
{
    ObservableCollection<KeyValuePair<DateTime, DateTime>> Jours { get; set; }
}

class TestClass : ITest
{
    public TestClass()
    {
        Jours = new ObservableCollection<KeyValuePair<DateTime, DateTime>>();
        Jours.Add(new KeyValuePair<DateTime, DateTime>(DateTime.Now, DateTime.Now));
        Jours.Add(new KeyValuePair<DateTime, DateTime>(DateTime.Now, DateTime.Now));
        Jours.Add(new KeyValuePair<DateTime, DateTime>(DateTime.Now, DateTime.Now));
    }

    public ObservableCollection<KeyValuePair<DateTime, DateTime>> Jours { get; set; }
}