Using MEF in a Windows Store App: Listing 4

MainPage.xaml class.

using System;
using System.Collections.Generic;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Navigation;
using System.Composition;
using System.Composition.Hosting;
using System.Reflection;

// The Blank Page item template is documented at

namespace VSMMefDemo
    /// <summary>
    /// An empty page that can be used on its own or navigated to within a Frame.
    /// </summary>
    public sealed partial class MainPage : Page
        public IEnumerable<Lazy<BusinessRules.IValidate, BusinessRules.ValidateMetaData>> Validators { get; private set; }
        private BusinessRules.IValidate _selectedValidator;

        public MainPage()

            var configuration = new ContainerConfiguration()

            var compositionHost = configuration.CreateContainer();

            ValidationTypes.DataContext = Validators;

        /// <summary>
        /// Invoked when this page is about to be displayed in a Frame.
        /// </summary>
        /// <param name="e">Event data that describes how this page was reached.  The Parameter
        /// property is typically used to configure the page.</param>
        protected override void OnNavigatedTo(NavigationEventArgs e)

        private void Validate_Click(object sender, RoutedEventArgs e)
            if (_selectedValidator == null)
                Result.Text = "No validator was found.";
                Result.Text = _selectedValidator.Validate(Input.Text);

        private void ValidationTypes_SelectionChanged(object sender, SelectionChangedEventArgs e)
            if (e.AddedItems.Count > 0)
                _selectedValidator = ValidationTypes.SelectedValue as BusinessRules.IValidate;

About the Author

Eric Vogel is a Senior Software Developer for Red Cedar Solutions Group in Okemos, Michigan. He is the president of the Greater Lansing User Group for .NET. Eric enjoys learning about software architecture and craftsmanship, and is always looking for ways to create more robust and testable applications. Contact him at [email protected].

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