Dynamic Localizability—Updating the UI When the Culture Changes

The Windows Phone XAML data-binding infrastructure relies on change notification to signal that a property in a data-binding expression should be reevaluated. Generated resource designer classes do not provide change notification. Simply exposing the generated resource class for data-binding does not allow the UI to be updated when a culture change occurs at runtime. Therefore, some other means is required to update the UI when the app’s culture changes. This is the purpose of the custom BindableChangeNotifier class, shown in Listing 19.2. By using the BindableChangeNotifier class to wrap the resource’s designer class, change notification can be surreptitiously added for all properties.

The ResourceBase class implements System.ComponentModel.INotifyPropertyChanged to signal to the data-binding infrastructure that properties should be reread (see Listing 19.2).

LISTING 19.2. BindableChangeNotifier Class

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public sealed class BindableChangeNotifier<T> : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    static T instance;

    public T Instance
    {
        get
        {
            return instance;
        }
    }

    public BindableChangeNotifier(T observableObject)
    {
        instance = observableObject;
    }

    public void RaisePropertyChanged()
    {
        var temp = PropertyChanged;
        if (temp != null)
        {
            temp(this, new PropertyChangedEventArgs(string.Empty));
        }
    }
}

The BindableChangeNotifier class contains a public method called RaisePropertyChanged. By using string.Empty as the property name, it signals to the data-binding infrastructure that all source properties within the resources object should be reread. Thus, it is not necessary to raise the PropertyChanged event for each resource property.