ASP.Net Core 3.1 With Autofac ConfigureServices returning an System.IServiceProvider isn't supported.

前言

Autofac在ASP.Net Core3.0以后，集成方式有所调整。在ASP.Net Core2中我们一般是把Startup的ConfigureServices方法返回值类型改为IServiceProvider。我们可以先看一下部分代码：

1        public IServiceProvider ConfigureServices(IServiceCollection services)
2        {
3            
4            services.AddMvc();
5			//xxxxxx你的其他代码 省略...........
6            //用Autofac来替换IOC容器 返回值由 void 修改为 IServiceProvider
7            var containerBuilder = new ContainerBuilder();
8            containerBuilder.RegisterModule<CustomAutofacModule>();
9            containerBuilder.Populate(services);
10            var container = containerBuilder.Build();
11            //将当前的容器保存起来，用于后续使用
12            AutofacHelper.Container = container;
13            return new AutofacServiceProvider(container);
14        }

完整代码可以参考我之前的开源项目：LJD.APP:https://github.com/jellydong/LJDAPP

CustomAutofacModule是把Autofac的配置单独写，不然都放在Startup中有点臃肿。

我们把这段代码Copy到ASP.Net Core3.1的项目中启动：

异常：System.NotSupportedException:“ConfigureServices returning an System.IServiceProvider isn't supported.”

就是说，我们不能再这样修改返回值类型，

官网解释：您不能再IServiceProvider从中返回ConfigureServices，也不能将服务提供者工厂添加到服务集合中。

那我们按照官方文档的方法修改一下。

建立ASP.Net Core3.1 Web项目

效果图

Services

创建完成后我们先创建文件夹Services,用来测试使用。

在Services文件夹下创建Iservice

1namespace DotNetCore3AutoFac.Services
2{
3    public interface IService
4    {
5        string SayHi();
6    }
7}

然后创建两个Iservice的实现类OneService、TwoService

1namespace DotNetCore3AutoFac.Services
2{
3    public class OneService:IService
4    {
5        public string SayHi()
6        {
7            return "One Say Hi";
8        }
9    }
10}
11
12
13namespace DotNetCore3AutoFac.Services
14{
15    public class TwoService:IService
16    {
17        public string SayHi()
18        {
19            return "Two Say Hi";
20        }
21    }
22}

Autofac

创建Autofac文件夹，在该文件夹下创建CustomAutofacModule

1using Autofac;
2using DotNetCore3AutoFac.Services;
3
4namespace DotNetCore3AutoFac.Autofac
5{
6    public class CustomAutofacModule : Module
7    {
8        /// <summary>
9        /// AutoFac注册类
10        /// </summary>
11        /// <param name="builder"></param>
12        protected override void Load(ContainerBuilder builder)
13        {
14            builder.RegisterType<OneService>().As<IService>();
15        }
16    }
17}

我们先用OneService去实现，当然，正常这里会有很多很多的代码~

修改Startup和Program

当然，需要安装Autofac的包：Autofac&Autofac.Extensions.DependencyInjection

前序工作都完成了，我们来改最重要的，首先修改我们的Program，增加UseServiceProviderFactory(new AutofacServiceProviderFactory())

1namespace DotNetCore3AutoFac
2{
3    public class Program
4    {
5        public static void Main(string[] args)
6        {
7            CreateHostBuilder(args).Build().Run();
8        }
9
10        public static IHostBuilder CreateHostBuilder(string[] args) =>
11            Host.CreateDefaultBuilder(args)
12            	//改用Autofac来实现依赖注入
13                .UseServiceProviderFactory(new AutofacServiceProviderFactory())
14                .ConfigureWebHostDefaults(webBuilder =>
15                {
16                    webBuilder.UseStartup<Startup>();
17                });
18    }
19}
20

然后我们修改Startup

1、增加属性AutofacContainer

2、增加方法ConfigureContainer它在ConfigureServices之后运行

3、给属性赋值（可选）

1using Autofac;
2using Autofac.Extensions.DependencyInjection;
3using DotNetCore3AutoFac.Autofac; 
4using Microsoft.AspNetCore.Builder;
5using Microsoft.AspNetCore.Hosting;
6using Microsoft.Extensions.Configuration;
7using Microsoft.Extensions.DependencyInjection;
8using Microsoft.Extensions.Hosting;
9
10namespace DotNetCore3AutoFac
11{
12    public class Startup
13    {
14        public Startup(IConfiguration configuration)
15        {
16            Configuration = configuration;
17        }
18
19        public IConfiguration Configuration { get; }
20		//autofac 新增
21        public ILifetimeScope AutofacContainer { get; private set; }
22
23
24        // This method gets called by the runtime. Use this method to add services to the container.
25        public void ConfigureServices(IServiceCollection services)
26        {
27            services.AddControllersWithViews(); 
28        }
29
30		//autofac 新增
31        public void ConfigureContainer(ContainerBuilder builder)
32        {
33            // 直接用Autofac注册我们自定义的 
34            builder.RegisterModule(new CustomAutofacModule());
35        }
36
37
38        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
39        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
40        {
41            if (env.IsDevelopment())
42            {
43                app.UseDeveloperExceptionPage();
44            }
45            else
46            {
47                app.UseExceptionHandler("/Home/Error");
48                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
49                app.UseHsts();
50            }
51			//autofac 新增 可选
52            this.AutofacContainer = app.ApplicationServices.GetAutofacRoot();
53
54
55            app.UseHttpsRedirection();
56            app.UseStaticFiles();
57
58            app.UseRouting();
59
60            app.UseAuthorization();
61
62            app.UseEndpoints(endpoints =>
63            {
64                endpoints.MapControllerRoute(
65                    name: "default",
66                    pattern: "{controller=Home}/{action=Index}/{id?}");
67            });
68        }
69    }
70}
71

验证

我们修改下HomeController

运行，断点看下结果是否正确

修改下实现类，也是正确的~

总结

其实很多官方文档都讲述了，因为自己近期打算把原来的项目LJD.APP:https://github.com/jellydong/LJDAPP升级到.Net Core 3.1上，当然是一个简化版本https://github.com/jellydong/Jelly.Simple。

所以不要怕英文，翻译插件那么好用，基本都能看懂的

参考文档：https://autofaccn.readthedocs.io/en/latest/integration/aspnetcore.html#asp-net-core-3-0-and-generic-hosting

当然Autofac的应用远不止这些，还有一个比原来好的就是可以实现AOP~