在WPF中使用.NET Core 3.0依賴項注入和服務提供程序

時間 2020-05-17

原文原文鏈接

前言

咱們都知道.NET Core提供了對依賴項注入的內置支持。咱們一般在ASP.NET Core中使用它（從Startup.cs文件中的ConfigureServices方法開始），可是該功能不限於此框架，咱們能夠在WPF和Windows Forms應用程序中使用它。git

實踐

新建項目
將所需的NuGet包添加到項目中。
- Microsoft.Extensions.DependencyInjection
- Microsoft.Extensions.Options.ConfigurationExtensions
- Microsoft.Extensions.Configuration.Json
而後，將一個名爲appsettings.json的文件添加到項目的根文件夾。將其「構建操做」屬性設置爲「內容」，將「複製到輸出目錄」設置爲「複製」（若是較新）：
```
{
"AppSettings": {
    "AppName": "SampleNetCore3WpfDependencyInjection"
    }
}
```
建立一個AppSettings.cs文件來保存配置設置。該文件將映射咱們在appsettings.json中編寫的設置：
```
public class AppSettings
    {
        public string AppName { get; set; } 
    }
```

建立一個示例服務：

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

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

而後像往常同樣在IOC容器中註冊服務：github

services.AddScoped<ISampleService, SampleService>();

打開App.xaml文件並刪除Application類的StartupUri屬性。而後，咱們須要重寫App.xaml.cs中的OnStartup方法：

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));
        }
    }

MainWindow簡單佈局及代碼改造

如上所述，MainWindow位於IOC容器中。所以，當咱們從服務提供商處得到服務時，它將自動注入全部必需的服務（若是有）。：json

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}";
        }
    }