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在Avalonia项目中使用MediatR和MS.DI库实现事件驱动通信

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大家好，我是沙漠尽头的狼！
AvaloniaUI是一个强大的跨平台.NET客户端开发框架，让开发者能够针对Windows、Linux、macOS、Android和iOS等多个平台构建应用程序。在构建复杂的应用程序时，模块化和组件间的通信变得尤为重要。Prism框架提供了模块化的开发方式，支持插件的热拔插，而MediatR则是一个实现了中介者（Mediator）模式的事件订阅发布框架，非常适合用于模块之间以及模块与主程序之间的通信。
本文重点是介绍MediatR，它 是 .NET 中的开源简单中介者模式实现。它通过一种进程内消息传递机制（无其他外部依赖），进行请求/响应、命令、查询、通知和事件的消息传递，并通过泛型来支持消息的智能调度。开源库地址是 https://github.com/jbogard/MediatR。
本文将详细介绍如何在Avalonia项目中使用MediatR和Microsoft的依赖注入（MS.DI）库来实现事件驱动的通信。

0. 基础知识准备-MediatR的基本用法

MediatR中有两种消息传递的方式：

  • Request/Response，用于一个单独的Handler。
  • Notification，用于多个Handler。
Request/Response

Request/Response 有点类似于 HTTP 的 Request/Response，发出一个 Request 会得到一个 Response。
Request 消息在 MediatR 中，有两种类型：

  • IRequest 返回一个T类型的值。
  • IRequest 不返回值。
对于每个 request 类型，都有相应的 handler 接口：

  • IRequestHandler 实现该接口并返回 Task<U>
  • RequestHandler 继承该类并返回 U
  • IRequestHandler 实现该接口并返回 Task
  • AsyncRequestHandler 继承该类并返回 Task
  • RequestHandler 继承该类不返回
Notification

Notification 就是通知，调用者发出一次，然后可以有多个处理者参与处理。

1. 准备工作

首先，确保你的Avalonia项目中已经安装了必要的NuGet包。你将需要Prism.DryIoc.Avalonia作为依赖注入容器，以及MediatR来处理事件的发布和订阅。此外，为了将MediatR集成到DryIoc容器中，你还需要DryIoc.Microsoft.DependencyInjection包（这里感谢网友寒提供的技术解答）。
在项目的.csproj文件或NuGet包管理器中添加以下引用：
  1. <PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  2. <PackageReference Include="MediatR" Version="12.2.0" />  
  3. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />
复制代码
2. 配置容器和注册服务

在Avalonia项目中，你需要配置DryIoc容器以使用Microsoft的DI扩展，并注册MediatR服务。这通常在你的主启动类（如App.axaml.cs）中完成。
以下是配置容器和注册服务的示例代码：
  1. namespace CodeWF.Tools.Desktop;public class App : PrismApplication{<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  2. <PackageReference Include="MediatR" Version="12.2.0" />  
  3. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> // 省略了模块注入等和主题无关的代码，有兴趣源码在文末可查<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  4. <PackageReference Include="MediatR" Version="12.2.0" />  
  5. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> ///<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  6. <PackageReference Include="MediatR" Version="12.2.0" />  
  7. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  /// 1、DryIoc.Microsoft.DependencyInjection低版本可不要这个方法（5.1.0及以下）<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  8. <PackageReference Include="MediatR" Version="12.2.0" />  
  9. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> /// 2、高版本必须，否则会抛出异常：System.MissingMethodException:“Method not found: 'DryIoc.Rules DryIoc.Rules.WithoutFastExpressionCompiler()'.”<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  10. <PackageReference Include="MediatR" Version="12.2.0" />  
  11. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> /// 参考issues：https://github.com/dadhi/DryIoc/issues/529<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  12. <PackageReference Include="MediatR" Version="12.2.0" />  
  13. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> ///<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  14. <PackageReference Include="MediatR" Version="12.2.0" />  
  15. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  ///<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  16. <PackageReference Include="MediatR" Version="12.2.0" />  
  17. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  protected override Rules CreateContainerRules()<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  18. <PackageReference Include="MediatR" Version="12.2.0" />  
  19. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> {<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  20. <PackageReference Include="MediatR" Version="12.2.0" />  
  21. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  22. <PackageReference Include="MediatR" Version="12.2.0" />  
  23. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  return Rules.Default.WithConcreteTypeDynamicRegistrations(reuse: Reuse.Transient)<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  24. <PackageReference Include="MediatR" Version="12.2.0" />  
  25. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  26. <PackageReference Include="MediatR" Version="12.2.0" />  
  27. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  28. <PackageReference Include="MediatR" Version="12.2.0" />  
  29. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  30. <PackageReference Include="MediatR" Version="12.2.0" />  
  31. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />.With(Made.Of(FactoryMethod.ConstructorWithResolvableArguments))<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  32. <PackageReference Include="MediatR" Version="12.2.0" />  
  33. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  34. <PackageReference Include="MediatR" Version="12.2.0" />  
  35. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  36. <PackageReference Include="MediatR" Version="12.2.0" />  
  37. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  38. <PackageReference Include="MediatR" Version="12.2.0" />  
  39. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />.WithFuncAndLazyWithoutRegistration()<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  40. <PackageReference Include="MediatR" Version="12.2.0" />  
  41. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  42. <PackageReference Include="MediatR" Version="12.2.0" />  
  43. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  44. <PackageReference Include="MediatR" Version="12.2.0" />  
  45. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  46. <PackageReference Include="MediatR" Version="12.2.0" />  
  47. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />.WithTrackingDisposableTransients()<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  48. <PackageReference Include="MediatR" Version="12.2.0" />  
  49. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  50. <PackageReference Include="MediatR" Version="12.2.0" />  
  51. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  52. <PackageReference Include="MediatR" Version="12.2.0" />  
  53. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  54. <PackageReference Include="MediatR" Version="12.2.0" />  
  55. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />//.WithoutFastExpressionCompiler()<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  56. <PackageReference Include="MediatR" Version="12.2.0" />  
  57. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  58. <PackageReference Include="MediatR" Version="12.2.0" />  
  59. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  60. <PackageReference Include="MediatR" Version="12.2.0" />  
  61. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  62. <PackageReference Include="MediatR" Version="12.2.0" />  
  63. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />.WithFactorySelector(Rules.SelectLastRegisteredFactory());<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  64. <PackageReference Include="MediatR" Version="12.2.0" />  
  65. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> }<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  66. <PackageReference Include="MediatR" Version="12.2.0" />  
  67. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> protected override IContainerExtension CreateContainerExtension()<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  68. <PackageReference Include="MediatR" Version="12.2.0" />  
  69. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> {<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  70. <PackageReference Include="MediatR" Version="12.2.0" />  
  71. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  72. <PackageReference Include="MediatR" Version="12.2.0" />  
  73. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  IContainer container = new Container(CreateContainerRules());<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  74. <PackageReference Include="MediatR" Version="12.2.0" />  
  75. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  76. <PackageReference Include="MediatR" Version="12.2.0" />  
  77. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  container.WithDependencyInjectionAdapter();<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  78. <PackageReference Include="MediatR" Version="12.2.0" />  
  79. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  80. <PackageReference Include="MediatR" Version="12.2.0" />  
  81. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  return new DryIocContainerExtension(container);<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  82. <PackageReference Include="MediatR" Version="12.2.0" />  
  83. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> }<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  84. <PackageReference Include="MediatR" Version="12.2.0" />  
  85. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> protected override void RegisterRequiredTypes(IContainerRegistry containerRegistry)<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  86. <PackageReference Include="MediatR" Version="12.2.0" />  
  87. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> {<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  88. <PackageReference Include="MediatR" Version="12.2.0" />  
  89. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  90. <PackageReference Include="MediatR" Version="12.2.0" />  
  91. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  base.RegisterRequiredTypes(containerRegistry);<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  92. <PackageReference Include="MediatR" Version="12.2.0" />  
  93. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  94. <PackageReference Include="MediatR" Version="12.2.0" />  
  95. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  IServiceCollection services = ConfigureServices();<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  96. <PackageReference Include="MediatR" Version="12.2.0" />  
  97. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  98. <PackageReference Include="MediatR" Version="12.2.0" />  
  99. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  IContainer container = ((IContainerExtension)containerRegistry).Instance;<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  100. <PackageReference Include="MediatR" Version="12.2.0" />  
  101. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  102. <PackageReference Include="MediatR" Version="12.2.0" />  
  103. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  container.Populate(services);<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  104. <PackageReference Include="MediatR" Version="12.2.0" />  
  105. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> }<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  106. <PackageReference Include="MediatR" Version="12.2.0" />  
  107. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> private static ServiceCollection ConfigureServices()<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  108. <PackageReference Include="MediatR" Version="12.2.0" />  
  109. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> {<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  110. <PackageReference Include="MediatR" Version="12.2.0" />  
  111. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  112. <PackageReference Include="MediatR" Version="12.2.0" />  
  113. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  var services = new ServiceCollection();<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  114. <PackageReference Include="MediatR" Version="12.2.0" />  
  115. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  116. <PackageReference Include="MediatR" Version="12.2.0" />  
  117. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  // 注入MediatR<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  118. <PackageReference Include="MediatR" Version="12.2.0" />  
  119. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  120. <PackageReference Include="MediatR" Version="12.2.0" />  
  121. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  var assemblies = AppDomain.CurrentDomain.GetAssemblies().ToList();<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  122. <PackageReference Include="MediatR" Version="12.2.0" />  
  123. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  124. <PackageReference Include="MediatR" Version="12.2.0" />  
  125. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  // 添加模块注入，未显示调用模块类型前，模块程序集是未加载到当前程序域`AppDomain.CurrentDomain`的<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  126. <PackageReference Include="MediatR" Version="12.2.0" />  
  127. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  128. <PackageReference Include="MediatR" Version="12.2.0" />  
  129. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  var assembly = typeof(SlugifyStringModule).GetAssembly();<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  130. <PackageReference Include="MediatR" Version="12.2.0" />  
  131. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  132. <PackageReference Include="MediatR" Version="12.2.0" />  
  133. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  assemblies.Add(assembly);<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  134. <PackageReference Include="MediatR" Version="12.2.0" />  
  135. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  136. <PackageReference Include="MediatR" Version="12.2.0" />  
  137. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  services.AddMediatR(configure =><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  138. <PackageReference Include="MediatR" Version="12.2.0" />  
  139. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  140. <PackageReference Include="MediatR" Version="12.2.0" />  
  141. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  {<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  142. <PackageReference Include="MediatR" Version="12.2.0" />  
  143. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  144. <PackageReference Include="MediatR" Version="12.2.0" />  
  145. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  146. <PackageReference Include="MediatR" Version="12.2.0" />  
  147. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  148. <PackageReference Include="MediatR" Version="12.2.0" />  
  149. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />configure.RegisterServicesFromAssemblies(assemblies.ToArray());<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  150. <PackageReference Include="MediatR" Version="12.2.0" />  
  151. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  152. <PackageReference Include="MediatR" Version="12.2.0" />  
  153. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  });<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  154. <PackageReference Include="MediatR" Version="12.2.0" />  
  155. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  156. <PackageReference Include="MediatR" Version="12.2.0" />  
  157. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  return services;<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  158. <PackageReference Include="MediatR" Version="12.2.0" />  
  159. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> }}
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在上面的代码中，我们重写了CreateContainerRules、CreateContainerExtension和RegisterRequiredTypes方法以配置DryIoc容器，并注册了MediatR服务和相关处理程序。
注意，在注册MediatR服务时，我们从当前已加载的程序集列表中查找并注册处理程序。如果模块是按需加载的，请确保在注册处理程序之前已加载了相应的模块。
此外，我们还演示了如何手动添加模块程序集到列表中以便注册处理程序。这通常在你需要显式控制哪些模块和处理程序被注册时很有用。但是，请注意，在大多数情况下，你可能希望使用更自动化的方式来加载和注册模块及处理程序（例如，通过扫描特定目录或使用约定等）。这取决于你的具体需求和项目结构。
另外，请注意代码中的注释和说明，它们提供了有关每个步骤和配置的额外信息。在实际项目中，你可能需要根据项目的实际情况和需求进行相应的调整和优化。例如，你可能需要处理循环依赖、配置作用域、使用拦截器或装饰器等高级功能。这些都可以在DryIoc和MediatR的文档中找到更详细的说明和示例。
3. MediatR2种传递方式

有了前面的基础知识准备，我们添加类库工程CodeWF.Tools.MediatR.Notifications，并添加请求定义（主工程及模块的响应处理程序需要实现）：
  1. public class TestRequest : IRequest{<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  2. <PackageReference Include="MediatR" Version="12.2.0" />  
  3. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> public string? Args { get; set; }}
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添加通知定义：
  1. public class TestNotification : INotification{<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  2. <PackageReference Include="MediatR" Version="12.2.0" />  
  3. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> public string? Args { get; set; }}
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请求和通知定义结构一样（实现接口不同），只有一个字符串属性。
4. 添加处理程序

示例工程结构如下，因为该开源项目（文末链接）写在站长的AvaloniaUI桌面工具工程，本文只关注如下图3个工程即可：

在AvaloniaUI主工程(CodeWF.Tools.Desktop)添加请求响应处理程序：
  1. public class TestHandler : IRequestHandler{<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  2. <PackageReference Include="MediatR" Version="12.2.0" />  
  3. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> public async Task Handle(TestRequest request, CancellationToken cancellationToken)<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  4. <PackageReference Include="MediatR" Version="12.2.0" />  
  5. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> {<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  6. <PackageReference Include="MediatR" Version="12.2.0" />  
  7. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  8. <PackageReference Include="MediatR" Version="12.2.0" />  
  9. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  return await Task.FromResult($"主工程处理程序：Args = {request.Args}, Now = {DateTime.Now}");<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  10. <PackageReference Include="MediatR" Version="12.2.0" />  
  11. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> }}
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添加通知响应处理程序：
  1. public class TestNotificationHandler(INotificationService notificationService) : INotificationHandler{<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  2. <PackageReference Include="MediatR" Version="12.2.0" />  
  3. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> public Task Handle(TestNotification notification, CancellationToken cancellationToken)<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  4. <PackageReference Include="MediatR" Version="12.2.0" />  
  5. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> {<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  6. <PackageReference Include="MediatR" Version="12.2.0" />  
  7. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  8. <PackageReference Include="MediatR" Version="12.2.0" />  
  9. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  notificationService.Show("Notification",<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  10. <PackageReference Include="MediatR" Version="12.2.0" />  
  11. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  12. <PackageReference Include="MediatR" Version="12.2.0" />  
  13. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  14. <PackageReference Include="MediatR" Version="12.2.0" />  
  15. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  16. <PackageReference Include="MediatR" Version="12.2.0" />  
  17. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />$"主工程Notification处理程序：Args = {notification.Args}, Now = {DateTime.Now}");<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  18. <PackageReference Include="MediatR" Version="12.2.0" />  
  19. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  20. <PackageReference Include="MediatR" Version="12.2.0" />  
  21. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  return Task.CompletedTask;<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  22. <PackageReference Include="MediatR" Version="12.2.0" />  
  23. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> }}
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在模块【CodeWF.Tools.Modules.SlugifyString】中添加请求响应处理程序(因为顺序关系，不会触发，这里添加只是演示请求为一对一响应）：
  1. public class TestHandler : IRequestHandler{<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  2. <PackageReference Include="MediatR" Version="12.2.0" />  
  3. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> public async Task Handle(TestRequest request, CancellationToken cancellationToken)<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  4. <PackageReference Include="MediatR" Version="12.2.0" />  
  5. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> {<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  6. <PackageReference Include="MediatR" Version="12.2.0" />  
  7. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  8. <PackageReference Include="MediatR" Version="12.2.0" />  
  9. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  return await Task.FromResult($"模块【SlugifyString】Request处理程序：Args = {request.Args}, Now = {DateTime.Now}");<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  10. <PackageReference Include="MediatR" Version="12.2.0" />  
  11. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> }}
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添加通知响应处理程序（会和主工程通知响应处理程序一样被触发）：
  1. public class TestNotificationHandler(INotificationService notificationService) : INotificationHandler{<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  2. <PackageReference Include="MediatR" Version="12.2.0" />  
  3. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> public Task Handle(TestNotification notification, CancellationToken cancellationToken)<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  4. <PackageReference Include="MediatR" Version="12.2.0" />  
  5. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> {<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  6. <PackageReference Include="MediatR" Version="12.2.0" />  
  7. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  8. <PackageReference Include="MediatR" Version="12.2.0" />  
  9. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  notificationService.Show("Notification",<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  10. <PackageReference Include="MediatR" Version="12.2.0" />  
  11. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  12. <PackageReference Include="MediatR" Version="12.2.0" />  
  13. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  14. <PackageReference Include="MediatR" Version="12.2.0" />  
  15. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  16. <PackageReference Include="MediatR" Version="12.2.0" />  
  17. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />$"模块【SlugifyString】Notification处理程序：Args = {notification.Args}, Now = {DateTime.Now}");<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  18. <PackageReference Include="MediatR" Version="12.2.0" />  
  19. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  20. <PackageReference Include="MediatR" Version="12.2.0" />  
  21. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  return Task.CompletedTask;<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  22. <PackageReference Include="MediatR" Version="12.2.0" />  
  23. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> }}
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几个响应处理程序类定义类似：收到请求时，返回格式化字符串；收到通知时，弹出提示表明当前是哪个位置收到的通知，便于演示效果。
5. 请求和通知演示

触发操作我们写在模块【CodeWF.Tools.Modules.SlugifyString】中，在模块的ViewModel类里通过依赖注入获取请求和通知的发送者实例ISender和IPublisher：
  1. using Unit = System.Reactive.Unit;namespace CodeWF.Tools.Modules.SlugifyString.ViewModels;public class SlugifyViewModel : ViewModelBase{<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  2. <PackageReference Include="MediatR" Version="12.2.0" />  
  3. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> // 省略别名转换相关逻辑代码，源码文末查看<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  4. <PackageReference Include="MediatR" Version="12.2.0" />  
  5. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  6. <PackageReference Include="MediatR" Version="12.2.0" />  
  7. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  private readonly INotificationService _notificationService;<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  8. <PackageReference Include="MediatR" Version="12.2.0" />  
  9. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> private readonly IClipboardService? _clipboardService;<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  10. <PackageReference Include="MediatR" Version="12.2.0" />  
  11. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> private readonly ITranslationService? _translationService;<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  12. <PackageReference Include="MediatR" Version="12.2.0" />  
  13. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> public SlugifyViewModel(INotificationService notificationService, IClipboardService clipboardService,<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  14. <PackageReference Include="MediatR" Version="12.2.0" />  
  15. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  16. <PackageReference Include="MediatR" Version="12.2.0" />  
  17. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  ITranslationService translationService, ISender sender, IPublisher publisher) : base(sender, publisher)<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  18. <PackageReference Include="MediatR" Version="12.2.0" />  
  19. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> {<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  20. <PackageReference Include="MediatR" Version="12.2.0" />  
  21. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  22. <PackageReference Include="MediatR" Version="12.2.0" />  
  23. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  _notificationService = notificationService;<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  24. <PackageReference Include="MediatR" Version="12.2.0" />  
  25. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  26. <PackageReference Include="MediatR" Version="12.2.0" />  
  27. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  _clipboardService = clipboardService;<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  28. <PackageReference Include="MediatR" Version="12.2.0" />  
  29. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  30. <PackageReference Include="MediatR" Version="12.2.0" />  
  31. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  _translationService = translationService;<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  32. <PackageReference Include="MediatR" Version="12.2.0" />  
  33. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  34. <PackageReference Include="MediatR" Version="12.2.0" />  
  35. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  KindChanged = ReactiveCommand.Create(OnKindChanged);<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  36. <PackageReference Include="MediatR" Version="12.2.0" />  
  37. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> }<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  38. <PackageReference Include="MediatR" Version="12.2.0" />  
  39. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> public async Task ExecuteMediatRRequestAsync()<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  40. <PackageReference Include="MediatR" Version="12.2.0" />  
  41. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> {<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  42. <PackageReference Include="MediatR" Version="12.2.0" />  
  43. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  44. <PackageReference Include="MediatR" Version="12.2.0" />  
  45. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  var result = Sender.Send(new TestRequest() { Args = To });<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  46. <PackageReference Include="MediatR" Version="12.2.0" />  
  47. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  48. <PackageReference Include="MediatR" Version="12.2.0" />  
  49. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  _notificationService.Show("MediatR", $"收到响应：{result.Result}");<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  50. <PackageReference Include="MediatR" Version="12.2.0" />  
  51. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> }<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  52. <PackageReference Include="MediatR" Version="12.2.0" />  
  53. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> public async Task ExecuteMediatRNotificationAsync()<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  54. <PackageReference Include="MediatR" Version="12.2.0" />  
  55. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> {<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  56. <PackageReference Include="MediatR" Version="12.2.0" />  
  57. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /><PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  58. <PackageReference Include="MediatR" Version="12.2.0" />  
  59. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" />  await Publisher.Publish(new TestNotification() { Args = To });<PackageReference Include="Prism.DryIoc.Avalonia" Version="8.1.97.11072" />
  60. <PackageReference Include="MediatR" Version="12.2.0" />  
  61. <PackageReference Include="DryIoc.Microsoft.DependencyInjection" Version="8.0.0-preview-01" /> }}
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点击测试MediatR-Request按钮触发调用ISender.Send发出请求并得到响应，通过点击测试MediatR-Notification按钮触发调用IPublisher.Publish发出通知。
请求效果：

看上面的请求效果：虽然在主工程和模块工程都注册了一个响应，但只有主工程被触发。
通知效果：

在主工程和模块工程都注册了一个通知响应，所以两个处理程序都弹出了提示。
6. 总结

为什么使用MediatR，而未使用Prism的事件聚合器？

站长开发工具做了在线版(https://blazor.dotnet9.com)，也做了跨平台桌面版本（AvaloniaUI），两个版本使用MediatR可以复用大部分事件代码。
CQRS or DDD?

这节直接复制MediatR 在 .NET 应用中的实践 - 明志唯新 (yimingzhi.net)，大家应该可以学到些什么：
软件开发发展到今天，模式和理念不断在架构中刷新：从分布式到微服务，再到云原生 ……。时代对一个程序员，尤其是服务端程序员，提出的要求越来越高。DDD（领域驱动设计）在微服务架构中一再被提及，甚至有人提出这是必须项！
实施一个完美的 DDD 还是有难度的，现实中奋战在一线的 CRUD 程序员还是不少。那么在 CRUD 和 DDD 之间我们是否还有缓冲区呢？MediatR 的作者曾经也撰文讨论过这个问题，我很认同他的基本观点：设计是为应用服务的，不能为了 DDD 而 DDD。
CQRS 的全称是："Command and Query Responsibility Segregation"，直译过来就是命令与查询责任分离，可以通俗的理解为 读写分离。

微软的官方文档中对此做过如下陈述：
CQRS 命令和查询责任分离数据存储的读取和更新操作分离的模式。 在应用程序中实现 CQRS 可以最大程度地提高其性能、可伸缩性和安全性。 通过迁移到 CQRS 而创建的灵活性使系统能够随着时间的推移更好地发展，并防止更新命令在域级别导致合并冲突。
微软也给出了相应的隔离模型解决方案：
CQRS 使用命令来更新数据，使用查询来读取数据，将读取和写入 分离到不同的 模型中。

  • 命令应基于任务，而不是以数据为中心。
  • 命令可以放置在队列中进行异步处理，而不是同步处理。
  • 查询从不修改数据库。 查询返回的 DTO 不封装任何域知识。

CQRS 的好处包括：


  • 独立缩放: CQRS 允许读取和写入工作负载独立缩放，这可能会减少锁争用。
  • 优化的数据架构: 读取端可使用针对查询优化的架构，写入端可使用针对更新优化的架构。
  • 安全性: 更轻松地确保仅正确的域实体对数据执行写入操作。
  • 关注点分离: 分离读取和写入端可使模型更易维护且更灵活。 大多数复杂的业务逻辑被分到写模型。 读模型会变得相对简单。
  • 查询更简单: 通过将具体化视图存储在读取数据库中，应用程序可在查询时避免复杂联接。
有了 MediatR 我们可以在应用中轻松实现 CQRS:

  • IRequest 的消息名称以 Command 为结尾的是命令，其对应的 Handler 执行写任务
  • IRequest 的消息名称以 Query 为结尾的是查询，其对应的 Handler 执行读数据
结束语

MediatR 是一个简单的中介者实现，可以极大降低我们的应用复杂度，也能够使得我们一路从 CRUD 到 CQRS 到 DDD 进行逐级演进。毕竟我们是生活在现实中的人，不能罔顾商业现实，纯粹一味追求技术。

商业技术的演进，应该是一路持续的改革而不是来一场革命。疫情总有反复，但是我们得活着，相对轻松的活着！
参考

文中示例写了主要代码，但可能缺失部分细节，源码链接如下，欢迎留言交流。
参考文章：MediatR 在 .NET 应用中的实践
本文源码：Github

来源:https://www.cnblogs.com/Dotnet9-com/p/18049805
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发表于 2024-3-3 17:26:44

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