试图了解 Caliburn Micro EventAggregator

Question

我了解 EventAggregator 在 Caliburn Micro 中的工作原理，但我不明白：

我们以此为例：

视图模型 A

private IEventAggregator _eventAggregator;
public ViewModelA(IEventAggregator eventAggregator)
{
   _eventAggregator = eventAggregator
   _eventAggregator.PublishOnUIThread("Hello");
}

ViewModel B

private IEventAggregator _eventAggregator;
public ViewModelA(IEventAggregator eventAggregator)
{
   _eventAggregator = eventAggregator
   _eventAggregator.Subscribe(this)
}
public void Handle(string message)
{ 
   MessageBox.Show(message + " From ViewModel B")
}

ViewModel C

private IEventAggregator _eventAggregator;
public ViewModelA(IEventAggregator eventAggregator)
{
   _eventAggregator = eventAggregator
   _eventAggregator.Subscribe(this)
}
public void Handle(string message)
{ 
   MessageBox.Show(message + " From ViewModel C")
}

那么我如何 select 在发布事件时使用哪个视图模型句柄？

Answer 1

So how can i select which viewmodel handle to use when i publish events?

多个视图模型可能会订阅同一条消息。这就是事件聚合的工作原理。发布者在不知道接收者数量的情况下发布一条消息。

如果您希望特定视图模型能够订阅事件，它应该实现 IHandle<T> 接口并调用事件聚合器上的 Subscribe 方法：

public class ViewModelA : IHandle<string>
{
    private readonly IEventAggregator _eventAggregator;

    public ViewModelA(IEventAggregator eventAggregator)
    {
        _eventAggregator = eventAggregator;
        _eventAggregator.Subscribe(this);
    }

    public void Handle(string message)
    {
        MessageBox.Show(message);
    }
}

执行此操作的所有视图模型都会收到消息。

Answer 2

我设法通过消息 class:

向特定视图模型发送消息

public class Message<TTarget, TValue>
{
    public TValue Value { get; set; }

    public Message(TValue value)
    {
        Value = value;
    }
}

然后添加到class

IHandle<Message<ViewModel, string>>

用法：

_eventAggregator.PublishOnUIThread(new Message<ViewModel, string>("Hello from ViewModel"));

试图了解 Caliburn Micro EventAggregator

Trying to understand Caliburn Micro EventAggregator

c#

wpf

mvvm

caliburn.micro

eventaggregator