Windows Phone 7 数据绑定与UI 刷新: Displaying Data with Data Binding

 Displaying Data with Data Binding

Change Notification

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In order for changes to the source object to propagate to the target, the source must implement the INotifyPropertyChanged interface. INotifyPropertyChanged has the PropertyChanged event, which tells the binding engine that the source has changed so that the binding engine can update the target value.

In the following example, the MyColors class implements the INotifyPropertyChanged interface for OneWay binding.

// Create a class that implements INotifyPropertyChanged.
public class MyColors : INotifyPropertyChanged
{
    private SolidColorBrush _Brush1;

    // Declare the PropertyChanged event.
    public event PropertyChangedEventHandler PropertyChanged;

    // Create the property that will be the source of the binding.
    public SolidColorBrush Brush1
    {
        get { return _Brush1; }
        set
        {
            _Brush1 = value;
            // Call NotifyPropertyChanged when the source property 
            // is updated.
            NotifyPropertyChanged("Brush1");
        }
    }


    // NotifyPropertyChanged will raise the PropertyChanged event, 
    // passing the source property that is being updated.
    public void NotifyPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, 
                new PropertyChangedEventArgs(propertyName));
        }
    }
}

To get change notification for collections bound to an ItemsControl, implement INotifyCollectionChanged in addition to INotifyPropertyChanged. If you implement INotifyCollectionChanged, changes to the collection, such as adding or removing an object, will propagate to the target. To get property change notification for objects in the collection, the objects must implement INotifyPropertyChanged.

Before implementing your own collection, consider using the ObservableCollection(Of T) class, which has a built-in implementation of INotifyCollectionChanged and INotifyPropertyChanged.