Caliburn第4部分 事件聚合器

The event aggregator is a service that makes it easy for multiple parts of your application to send messages to each other.

要做到这一点，你订阅的??事件聚合的对象（如视图模型），并指定他们应该听什么类型的消息。

现在做一个ColorViewModel，在AppViewModel中实现下列代码

public class AppViewModel : PropertyChangedBase
{
  public AppViewModel(ColorViewModel colorModel)
  {
    ColorModel = colorModel;
  }
 
  public ColorViewModel ColorModel { get; private set; }
}

<Grid Width="300" Height="300" Background="LightBlue">
  <Grid.ColumnDefinitions>
    <ColumnDefinition Width="*" />
    <ColumnDefinition Width="*" />
  </Grid.ColumnDefinitions>
  <ContentControl Name="ColorModel" Margin="10" />
</Grid>

AppBootstrapper 为了支持含有参数的构造函数

Make sure to include a reference to System.ComponentModel.Composition.dll to the application

using Caliburn.Micro;
using System.ComponentModel.Composition;
using System.ComponentModel.Composition.Hosting;
using System.ComponentModel.Composition.Primitives;
 
public class AppBootstrapper : Bootstrapper<AppViewModel>
{
  private CompositionContainer container;
 
  protected override void Configure()
  {
    container = new CompositionContainer(new AggregateCatalog(AssemblySource.Instance.Select(x => new AssemblyCatalog(x)).OfType<ComposablePartCatalog>()));
 
    CompositionBatch batch = new CompositionBatch();
 
    batch.AddExportedValue<IWindowManager>(new WindowManager());
    batch.AddExportedValue<IEventAggregator>(new EventAggregator());
    batch.AddExportedValue(container);
 
    container.Compose(batch);
  }
 
  protected override object GetInstance(Type serviceType,string key)
  {
    string contract = string.IsNullOrEmpty(key) ? AttributedModelServices.GetContractName(serviceType) : key;
    var exports = container.GetExportedValues<object>(contract);
 
    if (exports.Count() > 0)
    {
      return exports.First();
    }
 
    throw new Exception(string.Format("Could not locate any instances of contract {0}.",contract));
  }
}

Next,we need to include an Export attribute on both our view-model classes. This is for the GetInstance method in the AppBootstrapper to work.

[Export(typeof(AppViewModel))]
public class AppViewModel : PropertyChangedBase
{
  ...
}
 
[Export(typeof(ColorViewModel))]
public class ColorViewModel
{
}

And finally,include the ImportingConstructor attribute on the AppViewModel constructor.

This is to indicate that this constructor should be used since there is no default constructor. When Caliburn Micro creates the AppViewModel,it will also create an instance of the ColorViewModel to pass into the constructor for us.

[ImportingConstructor]
public AppViewModel(ColorViewModel colorModel)
{
  ColorModel = colorModel;
}

add a Rectangle into the second column

private SolidColorBrush _Color;
 
public SolidColorBrush Color
{
  get { return _Color; }
  set
  {
    _Color = value;
    NotifyOfPropertyChange(() => Color);
  }
}

<Rectangle Grid.Column="1" Width="100" Height="100" Fill="{Binding Color}" />

第2步：实施IHandle <TMessage>接口

We are going to be publishing messages from the ColorViewModel to be picked up by the AppViewModel.

添加一个消息类

public class ColorEvent
{
  public ColorEvent(SolidColorBrush color)
  {
    Color = color;
  }
 
  public SolidColorBrush Color { get; private set; }
}

In order for the AppViewModel to handle the appropriate events,it will need to implement the IHandle<TMessage> interface.
AppViewModel中添加事件

public void Handle(ColorEvent message)
{
  Color = message.Color;
}

订阅事件Now we need to subscribe the AppViewModel to an event aggregator so that it can actually listen to published messages.

[ImportingConstructor]
public AppViewModel(ColorViewModel colorModel,IEventAggregator events)
{
  ColorModel = colorModel;
 
  events.Subscribe(this);
}

步骤4：发布

The ColorViewModel is also going to need the event aggregator so that it can publish messages

private readonly IEventAggregator _events;
 
[ImportingConstructor]
public ColorViewModel(IEventAggregator events)
{
  _events = events;
}

ColorView

<RadioButton Name="Red" Content="Red" Foreground="White"
             VerticalAlignment="Center" HorizontalAlignment="Center" />
<RadioButton Name="Green" Content="Green" Foreground="White"
             VerticalAlignment="Center" HorizontalAlignment="Center" Grid.Row="1" />
<RadioButton Name="Blue" Content="Blue" Foreground="White"
             VerticalAlignment="Center" HorizontalAlignment="Center" Grid.Row="2" />

ColorViewModel

public void Red()
{
  _events.Publish(new ColorEvent(new SolidColorBrush(Colors.Red)));
}
 
public void Green()
{
  _events.Publish(new ColorEvent(new SolidColorBrush(Colors.Green)));
}
 
public void Blue()
{
  _events.Publish(new ColorEvent(new SolidColorBrush(Colors.Blue)));
}

http://www.mindscapehq.com/blog/index.php/2012/2/1/caliburn-micro-part-4-the-event-aggregator/

附MEF

1.CompositionContainer

（编辑：李大同）

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