在WPF中使用.NET Core 3.0依赖项注入和服务提供程序

前言

我们都知道.NET Core提供了对依赖项注入的内置支持。我们通常在ASP.NET Core中使用它（从Startup.cs文件中的ConfigureServices方法开始），但是该功能不限于此框架，我们可以在WPF和Windows Forms应用程序中使用它。

实践

1. 新建项目#

   

2. 将所需的NuGet包添加到项目中。#

   • Microsoft.Extensions.DependencyInjection
   • Microsoft.Extensions.Options.ConfigurationExtensions
   • Microsoft.Extensions.Configuration.Json
     

3. 然后，将一个名为appsettings.json的文件添加到项目的根文件夹。将其“ 构建操作”属性设置为“ 内容”，将“复制到输出目录”设置为“ 复制”（如果较新）：#

   Copy
   {
   "AppSettings": {
       "AppName": "SampleNetCore3WpfDependencyInjection"
       }
   }
   

4. 创建一个AppSettings.cs文件来保存配置设置。该文件将映射我们在appsettings.json中编写的设置：#

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   public class AppSettings
       {
           public string AppName { get; set; } 
       }
   

5. 创建一个示例服务：#

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   public interface ISampleService
       {
           Task<string> GetCurrentDate();
       }
   

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   public class SampleService : ISampleService
       {
           public async Task<string> GetCurrentDate() => 
           await Task.FromResult(DateTime.Now.ToLongDateString());
       }
   

   然后像往常一样在IOC容器中注册服务：

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   services.AddScoped<ISampleService, SampleService>();
   
   

6. 打开App.xaml文件并删除Application类的StartupUri属性。然后，我们需要重写App.xaml.cs中的OnStartup方法：#

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   public partial class App : Application
       {
           public IServiceProvider ServiceProvider { get; private set; }
           public IConfiguration Configuration { get; private set; }
   
           protected override void OnStartup(StartupEventArgs e)
           {
               var builder = new ConfigurationBuilder()
                   .SetBasePath(Directory.GetCurrentDirectory())
                   .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true);
   
               Configuration = builder.Build();
   
               var serviceCollection = new ServiceCollection();
               ConfigureServices(serviceCollection);
   
               ServiceProvider = serviceCollection.BuildServiceProvider();
   
               var mainWindow = ServiceProvider.GetRequiredService<MainWindow>();
               mainWindow.Show();
           }
   
           private void ConfigureServices(IServiceCollection services)
           {
               services.Configure<AppSettings>(Configuration.GetSection(nameof(AppSettings)));
               services.AddScoped<ISampleService, SampleService>();
               services.AddTransient(typeof(MainWindow));
           }
       }
   

7. MainWindow简单布局及代码改造#

   如上所述，MainWindow位于IOC容器中。因此，当我们从服务提供商处获得服务时，它将自动注入所有必需的服务（如果有）。：

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   public partial class MainWindow : Window
       {
           private readonly ISampleService sampleService;
           private readonly AppSettings settings;
   
           public MainWindow(ISampleService sampleService,
               IOptions<AppSettings> settings)
           {
               InitializeComponent();
   
               this.sampleService = sampleService;
               this.settings = settings.Value;
           }
   
           private async void Button_Click(object sender, RoutedEventArgs e)
           {
               var serviceData =await sampleService.GetCurrentDate();
               var settingsData = settings;
               TextBox1.Text = $"serviceData:{serviceData}{Environment.NewLine}settingsData:{settings.AppName}";
           }
       }
   
   

   

8. Demo地址：github