c# - 如何使用 Microsoft.Extensions.DependencyInjection 在 .net 框架中的 webapi 中注入(inject)依赖项？

Question

我正在尝试按照以下说明将我的记录器作为依赖项注入(inject) .Net Framework 4.7.2 web api 项目中:

https://scottdorman.blog/2016/03/17/integrating-asp-net-core-dependency-injection-in-mvc-4/

这对 MVC web 应用程序非常有用，但在 webapi 项目上失败并出现“缺少无参数构造函数”错误。

如何在框架中仅使用默认程序集成功注入(inject):Microsoft.Extensions.DependencyInjection？

public class Startup
{
    public void Configuration(IAppBuilder app)
    {

        var services = new ServiceCollection();
        ConfigureServices(services);
        var resolver = new DefaultDependencyResolver(services.BuildServiceProvider());
        DependencyResolver.SetResolver(resolver);
    }

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllersAsServices(typeof(Startup).Assembly.GetExportedTypes()
            .Where(t => !t.IsAbstract && !t.IsGenericTypeDefinition)
            .Where(t => typeof(IController).IsAssignableFrom(t)
                        || t.Name.EndsWith("Controller", StringComparison.OrdinalIgnoreCase)));
        services.AddSingleton<IMyInterface , MyClass>();
    }
}
public class DefaultDependencyResolver : IDependencyResolver
{
    protected IServiceProvider serviceProvider;

    public DefaultDependencyResolver(IServiceProvider serviceProvider)
    {
        this.serviceProvider = serviceProvider;
    }

    public object GetService(Type serviceType)
    {
        return this.serviceProvider.GetService(serviceType);
    }

    public IEnumerable<object> GetServices(Type serviceType)
    {
        return this.serviceProvider.GetServices(serviceType);
    }
}

public static class ServiceProviderExtensions
{
    public static IServiceCollection AddControllersAsServices(this IServiceCollection services,
        IEnumerable<Type> controllerTypes)
    {
        foreach (var type in controllerTypes)
        {
            services.AddTransient(type);
        }

        return services;
    }
}

通过这样的注入(inject)获取“缺少无参数构造函数”错误:

private IMyInterface _my;
public HomeController(IMyInterface my)
{
    _my= my;
}

Answer 1

注册说明

一个问题是您正在使用 MVC 解析器注册 API 注册您的 DependencyResolver，不幸的是 is different from the WebAPI resolver registration API.你想要做的是:

public void Configuration(IAppBuilder app)
{    
    var services = new ServiceCollection();
    ConfigureServices(services);
    var resolver = new DefaultDependencyResolver(services.BuildServiceProvider());
    HttpConfiguration config = new HttpConfiguration();
    config.DependencyResolver = resolver;
    app.UseWebApi(config);
}

还要注意 IDependencyResolver 接口(interface) is defined separately in System.Web.Http ，因此您的 DefaultDependencyResolver 类需要更新为从它派生。

该接口(interface)的一个变化是有一个 BeginScope API。要实现它，请调用 CreateScope Extension Method在 Microsoft.Extensions.DependencyInjection 中的 IServiceProvider 上公开以获得新范围。然后将提供程序从该范围传递到您的 DefaultDependencyResolver 的新实例。

    public IDependencyScope BeginScope()
    {
        return new DefaultDependencyResolver(this.serviceProvider.CreateScope().ServiceProvider);
    }

完整示例

您关注的 MVC 博客示例使用的是 OWIN。当我开始做一个完整的例子时，我遇到了和你一样的错误，那是因为我没有正确配置 OWIN，所以 Startup 从未被调用过。以下是用于注入(inject) MVC 和 WebAPI Controller 的 Microsoft.Extensions.DependencyInjection 的完整工作示例:

https://github.com/ryandle/MVC_WebApi_DI_Example