在 ASP.NET 4.6.1 项目中集成 Microsoft.Extensions.DependencyInjection

Question

我的大部分项目都使用 .NET Core 3.1，但目前有一个使用 .NET Framework 4.6.1 的现有项目

我在实现对 .NET Framework 4.6.1 的依赖注入时遇到困难，不知道我哪里做错了。

这是我到目前为止所理解和所做的：

• .NET Framework 4.6.1 在运行时运行 Global.asax.cs -> Application_Start()
• .NET Core 3.1 在运行时运行 Startup.cs

这是在 .NET Core 3.1 中添加依赖注入的方式

Startup.cs

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllers();
        RegisterServices(services);

        ServiceProvider = services.BuildServiceProvider();
    }
    private void RegisterServices(IServiceCollection services)
    {
        services.AddOptions();
        services.AddTransient<IMemberServices, MemberService>();
    }

如何在 .NET Framework 4.6.1 中使用 MemberService 添加 IMemberServices 的依赖项

Global.asax.cs

public class WebApiApplication : System.Web.HttpApplication
{
    protected void Application_Start()
    {
        //What to write here?
    }
}

Answer 1

ASP.NET Web API 实现

警告：此答案在构建 MVC 网站时将不起作用。对于 MVC，请看我的其他回答。

假设您正在构建一个 ASP.NET Web API 应用程序，您将必须实现一个自定义 System.Web.Http.Dispatcher.IHttpControllerActivator 并替换您的 Application_Start 事件中的默认值。这是一个完整的工作示例，展示了如何将 Microsoft.Extensions.DependencyInjection (MS.DI) 集成到 ASP.NET Web API 4.6.1 及更高版本中：

using System.Web.Http;
using System.Web.Http.Dispatcher;
using System.Web.Mvc;
using System.Web.Optimization;
using System.Web.Routing;
using Microsoft.Extensions.DependencyInjection;

public class WebApiApplication : System.Web.HttpApplication
{
    protected void Application_Start()
    {
        AreaRegistration.RegisterAllAreas();
        GlobalConfiguration.Configure(WebApiConfig.Register);
        FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
        RouteConfig.RegisterRoutes(RouteTable.Routes);
        BundleConfig.RegisterBundles(BundleTable.Bundles);

        var services = new ServiceCollection();

        // Register all your controllers and other services here:
        services.AddTransient<Controllers.ValuesController>();

        var provider = services.BuildServiceProvider(new ServiceProviderOptions
        {
            // Prefer to keep validation on at all times
            ValidateOnBuild = true,
            ValidateScopes = true
        });

        GlobalConfiguration.Configuration.Services.Replace(
            typeof(IHttpControllerActivator),
            new MsDiHttpControllerActivator(provider));
    }
}

using System;
using System.Net.Http;
using System.Web.Http.Controllers;
using System.Web.Http.Dispatcher;
using Microsoft.Extensions.DependencyInjection;

public class MsDiHttpControllerActivator : IHttpControllerActivator
{
    private readonly ServiceProvider provider;

    public MsDiHttpControllerActivator(ServiceProvider provider)
    {
        this.provider = provider;
    }

    public IHttpController Create(
        HttpRequestMessage request, HttpControllerDescriptor descriptor, Type type)
    {
        var scope = this.provider.CreateScope();
        request.RegisterForDispose(scope);
        return (IHttpController)scope.ServiceProvider.GetRequiredService(type);
    }
}

虽然也可以实现自定义IDependencyResolver 而不是IHttpControllerActivator，但使用控制器激活器更简单，因为您有一个明确的位置来启动新的IServiceScope。创建服务范围并从该范围解析控制器很重要，因为直接从根 IServiceProvider 解析控制器会导致内存泄漏和多线程问题。

Answer 2

ASP.NET MVC 实现

警告：此答案在构建 Web API 网站时将不起作用。对于 Web API，请参阅我的其他答案。

假设您正在构建一个 ASP.NET MVC 应用程序，您将必须实现一个自定义 System.Web.Mvc.IControllerFactory 并替换您的 Application_Start 事件中的默认值。这是一个完整的工作示例，展示了如何将 Microsoft.Extensions.DependencyInjection (MS.DI) 集成到 ASP.NET MVC 4.6.1 及更高版本中：

using System.Web.Mvc;
using System.Web.Optimization;
using System.Web.Routing;
using Microsoft.Extensions.DependencyInjection;

public class MvcApplication : System.Web.HttpApplication
{
    protected void Application_Start()
    {
        AreaRegistration.RegisterAllAreas();
        FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
        RouteConfig.RegisterRoutes(RouteTable.Routes);
        BundleConfig.RegisterBundles(BundleTable.Bundles);

        var services = new ServiceCollection();

        // Register all your controllers and other services here:
        services.AddTransient<HomeController>();

        var provider = services.BuildServiceProvider(new ServiceProviderOptions
        {
            // Prefer to keep validation on at all times
            ValidateOnBuild = true,
            ValidateScopes = true
        });

        ControllerBuilder.Current.SetControllerFactory(
            new MsDiControllerFactory(provider));
    }
}

using System;
using System.Web;
using System.Web.Mvc;
using System.Web.Routing;
using Microsoft.Extensions.DependencyInjection;

public class MsDiControllerFactory : DefaultControllerFactory
{
    private readonly ServiceProvider provider;

    public MsDiControllerFactory(ServiceProvider provider) => this.provider = provider;

    protected override IController GetControllerInstance(
        RequestContext requestContext, Type controllerType)
    {
        IServiceScope scope = this.provider.CreateScope();

        HttpContext.Current.Items[typeof(IServiceScope)] = scope;

        return (IController)scope.ServiceProvider.GetRequiredService(controllerType);
    }

    public override void ReleaseController(IController controller)
    {
        base.ReleaseController(controller);

        var scope = HttpContext.Current.Items[typeof(IServiceScope)] as IServiceScope;

        scope?.Dispose();
    }
}

虽然也可以实现自定义IDependencyResolver 而不是IControllerFactory，但使用控制器工厂更简单，因为您有一个明确的位置来开始一个新的IServiceScope。创建服务范围并从该范围解析控制器很重要，因为直接从根 IServiceProvider 解析控制器会导致内存泄漏和多线程问题。