#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。