#1024程序员节｜征文#

不废话，直接上代码一个简单的示例。

1、事件聚合

创建一个文件夹EventBLL，添加EventDemo.cs，代码如下。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace WpfApp1.EventBLL
{public class EventDemo :PubSubEvent<string>{}
}

MainWindowViewModel.cs代码如下。

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using WpfApp1.EventBLL;namespace WpfApp1.ViewModels
{public class MainWindowViewModel : BindableBase{private string _mvvmString = "Hello Prism";public string MVVMString{get { return _mvvmString; }set { SetProperty(ref _mvvmString, value); }}private IEventAggregator _eventAggregator;public MainWindowViewModel(IEventAggregator ea){_eventAggregator = ea;_eventAggregator.GetEvent<EventDemo>().Subscribe(GetEvent);}private void GetEvent(string str){MVVMString = "接收到：" + str;}private DelegateCommand _EventPublishCommand;public DelegateCommand EventPublishCommand{get { return _EventPublishCommand = new DelegateCommand(EventPublish); }}private void EventPublish(){_eventAggregator.GetEvent<EventDemo>().Publish("123");}}
}

MainWindow.xaml 修改代码如下。

<Window x:Class="WpfApp1.Views.MainWindow"xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"xmlns:d="http://schemas.microsoft.com/expression/blend/2008"xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"xmlns:local="clr-namespace:WpfApp1"xmlns:prism="http://prismlibrary.com/"xmlns:i="http://schemas.microsoft.com/xaml/behaviors"mc:Ignorable="d"Title="MainWindow" Height="450" Width="800"><StackPanel><TextBlock Text="{Binding MVVMString}" FontSize="16" HorizontalAlignment="Center" VerticalAlignment="Center"/><Button Content="发布" Command="{Binding EventPublishCommand}" Width="200" Height="30" HorizontalAlignment="Center" Margin="0,0,0,5"/></StackPanel>
</Window>

运行效果如下图。

 2、订阅过滤

ThreadOption:下列选择可供选择。
    PublisherThread: 使用此设置接收发布者线程上的事件。这是默认设置。
    BackgroundThread: 使用此设置异步接收A上的事件。网框架线池线。
    UIThread: 使用此设置接收UI线程上的事件。

运行效果如图，通过下图可以看出当发布的是123是能够接收到。当发布的内容是23时没有接收到。这是因为订阅中过滤了不包含1的消息。

 MainWindow.xaml代码如下。

<Window x:Class="WpfApp1.Views.MainWindow"xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"xmlns:d="http://schemas.microsoft.com/expression/blend/2008"xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"xmlns:local="clr-namespace:WpfApp1"xmlns:prism="http://prismlibrary.com/"xmlns:i="http://schemas.microsoft.com/xaml/behaviors"mc:Ignorable="d"Title="MainWindow" Height="450" Width="800"><StackPanel><TextBlock Text="{Binding MVVMString}" FontSize="16" HorizontalAlignment="Center" VerticalAlignment="Center"/><TextBox x:Name="tbMessage" HorizontalAlignment="Center" Width="200" Height="30"/><Button Content="发布" Command="{Binding EventPublishCommand}" CommandParameter="{Binding ElementName=tbMessage,Path=Text}" Width="200" Height="30" HorizontalAlignment="Center" Margin="0,0,0,5"/></StackPanel>
</Window>

 MainWindowViewModel.cs代码如下。

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using WpfApp1.EventBLL;namespace WpfApp1.ViewModels
{public class MainWindowViewModel : BindableBase{private string _mvvmString = "Hello Prism";public string MVVMString{get { return _mvvmString; }set { SetProperty(ref _mvvmString, value); }}private IEventAggregator _eventAggregator;public MainWindowViewModel(IEventAggregator ea){_eventAggregator = ea;_eventAggregator.GetEvent<EventDemo>().Subscribe(GetEvent,ThreadOption.UIThread,false,(filter)=>filter.Contains("1"));}private void GetEvent(string str){MVVMString = "接收到：" + str;}private DelegateCommand<string> _EventPublishCommand;public DelegateCommand<string> EventPublishCommand{get { return _EventPublishCommand = new DelegateCommand<string>(EventPublish); }}private void EventPublish(string str){_eventAggregator.GetEvent<EventDemo>().Publish(str);}}
}

可以看到(filter)=>filter.Contains("1")，在这里对订阅进行了过滤，只有包含1的内容才能被接收到。

keepSubscriberReferenceAlive 参数是类型bool :

true ,事件实例保持对订阅实例的强引用,从而不允许它获得垃圾收集。
false(当此参数省略时的默认值),事件对订阅服务器实例保持弱引用,从而允许垃圾收集器在没有其他引用时处理订阅服务器实例。当收集订阅者实例时,事件将自动取消订阅。