Blend / XAML：通过按钮绑定ItemsSource

Question

I am creating a Windows 8.1 app and have the following code:

<ListView x:Name="listView" Height="505" Canvas.Left="35" Canvas.Top="75" Width="300" ItemTemplate="{StaticResource GroupTemplate}" ItemsSource="{Binding Groups, Mode=TwoWay, UpdateSourceTrigger=Explicit}" HorizontalAlignment="Left" VerticalAlignment="Top" UseLayoutRounding="False" ScrollViewer.VerticalScrollBarVisibility="Disabled" SelectionMode="None" />

<Button Height="40" Width="260" HorizontalAlignment="Left" VerticalAlignment="Top" Canvas.Left="40" Canvas.Top="585" BorderThickness="0" Content="Overige tonen" Background="#FF9B9B9B" Style="{StaticResource ButtonStyle1}"  Click="show_items2" />

When the user clicks the show_items2 button, the ItemsSource Groups should be replaced by another ItemsSource . I use sampledata 'Groups' from Blend for Visual Studio 2013. I have the pretty obvious code for the button, shown below:

private void show_Medicatie2(object sender, RoutedEventArgs e) 
        { 
           // replace itemsSource with another
        }

I've tried many tutorials but nothing seams to work. Do I miss something? Help is really appreciated. Thank you!

Answer 1

更改Groups时需要RaisePropertyChanged("Groups")

Answer 2

The class which you are binding to (in your case, the owner of Groups ) is required to be an INotifyPropertyChanged so that you can explicitly tell the WPF that the binding needs refreshing. This is a requirement if you are not using DependencyProperties .

Add this to your class definition:

class X : System.ComponentModel.INotifyPropertyChanged
{
    public event  System.ComponentModel.PropertyChangedEventHandler PropertyChanged;

    public IEnumerable<object> Groups //Replace 'object' with the type your are using...
    {
        get{ return m_Groups; }
        set
        {
            m_Groups = value;

            //Raise the event to notify that the property has actually got a new value
            var handler = PropertyChanged;
            if(handler != null)
                PropertyChanged(this, new PropertyChangedEventArgs("Groups"));
        }
    } IEnumerable<object> m_Groups = new List<object>();
}

Why does this work?

WPF knows about INotifyPropertyChanged and when you use an object as a Binding source, WPF checks if it implements the interface. If it does, WPF subscribes to the event. When the event is triggered, the property name is checked and if it matches the last property in the binding path , the binding is updated.

You can also replace IEnumerable<T> with ObservableCollection<T> but things start getting tricky soon afterwards. I recommended reading up about ObservableCollection<T> !