Gentle Introduction to MEF–Part Three

App.xaml

<Application x:Class="RealMef.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             StartupUri="MainWindow.xaml">
  <Application.Resources>
  </Application.Resources>
</Application>

App.xaml.cs

/// <summary>
/// Interaction logic for App.xaml
/// </summary>
public partial class App : Application
{
}

IGenerator.cs

[InheritedExport(typeof(IGenerator))]
public interface IGenerator
{
  string Name { get; }
  string Generate();
}

ITransformer.cs

[InheritedExport(typeof(ITransformer))]
public interface ITransformer
{
  string Name { get; }
  string Transform(string text);
}

MainWindow.xaml

<Window x:Class="RealMef.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="531" Width="979">
  <Grid>
    <Grid.RowDefinitions>
      <RowDefinition Height="20"/>
      <RowDefinition Height="*"/>
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
      <ColumnDefinition Width=".40*"/>
      <ColumnDefinition Width="200"/>
      <ColumnDefinition Width=".40*"/>
    </Grid.ColumnDefinitions>
    
    <StackPanel Grid.Row="0" Grid.Column="0" Orientation="Horizontal">
      <TextBlock Name="txtGeneratorType" HorizontalAlignment="Left"/>
      <Button Name="btnGenerate" Click="btnGenerate_Click" HorizontalAlignment="Right">Generate Source Data</Button>
    </StackPanel>
    <TextBox Grid.Row="1" Grid.Column="0" Name="txtSourceData" TextWrapping="Wrap"/>
    <StackPanel Grid.Row="1" Grid.Column="1" VerticalAlignment="Center" Margin="5,0">
      <ComboBox Name="cbTransformationOptions"/>
      <Button Name="btnTransform" Click="btnTransform_Click">Transform</Button>
      <Button Name="btnClear" Click="btnClear_Click">Clear Boxes</Button>
    </StackPanel>
    <TextBlock Grid.Row="1" Grid.Column="2" Name="txtDestinationData" TextWrapping="Wrap" Background="LightGray" Foreground="Blue"/>
  </Grid>
</Window>

MainWindow.xaml.cs

/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
  private readonly TranformationEngine _tranformationEngine;
  public MainWindow()
  {
    //  bootstrap MEF
    //  search the named assembly
    //using (var catalog = new AssemblyCatalog(Assembly.LoadFile(System.IO.Path.GetFullPath("TransformationImplementation.dll"))))
    //  search the directory
    using (var catalog = new DirectoryCatalog("."))
    {
      var container = new CompositionContainer(catalog);
      _tranformationEngine = new TranformationEngine();
      container.SatisfyImportsOnce(_tranformationEngine);
    }
    
    InitializeComponent();
    
    txtGeneratorType.Text = _tranformationEngine.Generator.Name;
    cbTransformationOptions.ItemsSource = _tranformationEngine.Transformers;
    cbTransformationOptions.DisplayMemberPath = "Name";
    cbTransformationOptions.SelectedIndex = 0;
  }
  
  private void btnGenerate_Click(object sender, RoutedEventArgs e)
  {
    txtSourceData.Text = _tranformationEngine.Generator.Generate();
  }
  
  private void btnClear_Click(object sender, RoutedEventArgs e)
  {
    txtSourceData.Text = txtDestinationData.Text = string.Empty;
  }
  
  private void btnTransform_Click(object sender, RoutedEventArgs e)
  {
    var transformer = cbTransformationOptions.SelectedItem as ITransformer;
    if (transformer != null)
    {
      txtDestinationData.Text = transformer.Transform(txtSourceData.Text);
    }
  }
}

ReverseTransformer.cs

public class ReverseTransformer : ITransformer
{
  #region Implementation of ITransformer
  public string Name
  {
    get { return "Reverse Transformer"; }
  }
  public string Transform(string text)
  {
    return new string(text.Reverse().ToArray());
  }
  #endregion
}

StarWarsTextGenerator.cs

[Export("StarWars", typeof(IGenerator))]
public class StarWarsTextGenerator : IGenerator
{
  #region Implementation of IGenerator
  public string Name
  {
    get { return "Star Wars Text Generator"; }
  }
  public string Generate()
  {
    return
      "Don't underestimate the Force. I suggest you try it again, Luke. This time, let go your conscious self and act on instinct. Look, I can take you as far as Anchorhead. You can get a transport there to Mos Eisley or wherever you're going. Partially, but it also obeys your commands. No! Alderaan is peaceful. We have no weapons. You can't possibly" +
      "You're all clear, kid. Let's blow this thing and go home! I find your lack of faith disturbing. The more you tighten your grip, Tarkin, the more star systems will slip through your fingers. What?! As you wish. I care. So, what do you think of her, Han?" +
      "Hey, Luke! May the Force be with you. Obi-Wan is here. The Force is with him. I can't get involved! I've got work to do! It's not that I like the Empire, I hate it, but there's nothing I can do about it right now. It's such a long way from here. I have traced the Rebel spies to her. Now she is my only link to finding their secret base." +
      "I'm surprised you had the courage to take the responsibility yourself. The Force is strong with this one. I have you now. But with the blast shield down, I can't even see! How am I supposed to fight? Ye-ha! Still, she's got a lot of spirit. I don't know, what do you think? Dantooine. They're on Dantooine." +
      "I don't know what you're talking about. I am a member of the Imperial Senate on a diplomatic mission to Alderaan-- I need your help, Luke. She needs your help. I'm getting too old for this sort of thing. Oh God, my uncle. How am I ever gonna explain this? I call it luck. Remember, a Jedi can feel the Force flowing through him.";
  }
  #endregion
}

TranformationEngine.cs

public class TranformationEngine
{
  [Import(typeof(IGenerator))]
  public IGenerator Generator { get; set; }
  [ImportMany(typeof(ITransformer))]
  public IEnumerable<ITransformer> Transformers { get; set; }
}