C# WPF的MVVM模式中使用消息的订阅和发布

C#的WPF开发中经常会遇到需要在不同窗口或者界面间传递消息，如果要严格遵循Model-View-ViewModel前后台分离的原则来开发的话，数据的跨界面传输就会比较麻烦，尤其涉及到多个不同界面间的相互交互。

PubSub库的订阅和发布可以比较方便的解决这个问题。

1. Model： 消息模型

using CommunityToolkit.Mvvm.ComponentModel;

namespace WpfPubSubDemo
{
    public partial class MessageModel: ObservableObject
    {
        [ObservableProperty]
        public string? sender;
        [ObservableProperty]
        public string message;
        public MessageModel()
        {
            Sender = null;
            Message = string.Empty;
        }
    }
}

2. View： 界面

2.1 主窗口MainWindow

Xaml

<Window x:Class="WpfPubSubDemo.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:WpfPubSubDemo"
        d:DataContext="{d:DesignInstance Type=local:MainViewModel}"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition></ColumnDefinition>
            <ColumnDefinition></ColumnDefinition>
        </Grid.ColumnDefinitions>
        <Frame x:Name="PageFrame"></Frame>
        <TextBlock Grid.Column="1" HorizontalAlignment="Center" Margin="0,134,0,0" TextWrapping="Wrap" d:Text="TextBlock" Text="{Binding MsgModel.Message}" VerticalAlignment="Top"/>
        <Label Grid.Column="1" Content="订阅者" HorizontalAlignment="Center" Margin="0,95,0,0" VerticalAlignment="Top"/>

    </Grid>
</Window>

CS

using System.Windows;


namespace WpfPubSubDemo
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {

        public MainViewModel viewModel { get; set; }

        public MainWindow()
        {
            InitializeComponent();
            viewModel = new MainViewModel();
            DataContext = viewModel;
            PageFrame.Navigate(new PageView());
        }
    }
}

2.2 子窗口PageView

Xaml

<Page x:Class="WpfPubSubDemo.PageView"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
      xmlns:local="clr-namespace:WpfPubSubDemo"
      d:DataContext="{d:DesignInstance Type=local:PageViewModel}"
      mc:Ignorable="d" 
      d:DesignHeight="450" d:DesignWidth="800"
      Title="PageView">

    <Grid Background="#FFFEFEFE">
        <TextBox x:Name="MsgTextBox" HorizontalAlignment="Center" Margin="0,113,0,0" TextWrapping="Wrap" Text="{Binding Msg.Message, Mode=TwoWay}" VerticalAlignment="Top" Width="120"/>
        <Button Content="发布" Command="{Binding PublishCommand}" HorizontalAlignment="Center" Margin="0,165,0,0" VerticalAlignment="Top"/>
        <Label Content="发布者" HorizontalAlignment="Center" Margin="0,73,0,0" VerticalAlignment="Top"/>

    </Grid>
</Page>

CS

using System.Windows.Controls;

namespace WpfPubSubDemo
{
    /// <summary>
    /// PageView.xaml 的交互逻辑
    /// </summary>
    public partial class PageView : Page
    {
        public PageViewModel pageViewModel;
        public PageView()
        {
            InitializeComponent();
            pageViewModel = new PageViewModel();
            DataContext = pageViewModel;
        }
    }
}

3. ViewModel：  逻辑调度

3.1 主窗体MainViewModel：

using CommunityToolkit.Mvvm.ComponentModel;
using PubSub;

namespace WpfPubSubDemo
{

    public partial class MainViewModel: ObservableObject
    {
        [ObservableProperty]
        public MessageModel msgModel;

        public Hub hub { get; set; }

        public MainViewModel()
        {
            MsgModel = new MessageModel();
            hub = Hub.Default;
            hub.Subscribe<MessageModel>((m) => MsgModel = m);

        }

    }

}

3.2 子窗口PageViewModel：

using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using PubSub;


namespace WpfPubSubDemo
{
    public partial class PageViewModel: ObservableObject
    {
        [ObservableProperty]
        public MessageModel msg;

        public PageViewModel()
        {
            Msg = new MessageModel();
            Msg.Message = "Init";
        }

        [RelayCommand]
        public void Publish()
        {
            Hub.Default.Publish(Msg);
        }
    }
}