Asp.Net Core 3.0以上，不再能通过修改Starup.ConfigureServices返回值（IServiceProvider），所以只能调用IHostBuilder.UseServiceProviderFactory修改最外层的IServiceProviderFactory，达到替换DI容器的目的。

流程是IHostBuilder.UseServiceProviderFactory->IHostBuilder.ConfigureServices->Starup.ConfigureServices，而且IHostBuilder.UseServiceProviderFactory不支持依赖注入，所以只能实例化了，不能取巧的IHostBuilder.ConfigureServices内注册IServiceProviderFactory。

配置Windsor注册模块

public interface IWindsorContainerModule
{
void Configure(WindsorContainer container);
}


这块不支持依赖注入，详情参考上文

自定义DI容器

核心模块 WindsorRegistrationHelper.CreateServiceProvider ，引用Nuget Castle.Windsor.MsDependencyInjection。

internal class WindsorContainerFactory : IServiceProviderFactory
{
private WindsorContainer container;
private IServiceCollection services;
public WindsorContainerFactory(IWindsorContainerModule containerModule)
{
cOntainer= new WindsorContainer();
containerModule.Configure(container);
}
public IServiceCollection CreateBuilder(IServiceCollection services)
{
this.services = services;
return services;
}
public IServiceProvider CreateServiceProvider(IServiceCollection containerBuilder)
{
return WindsorRegistrationHelper.CreateServiceProvider(container, services);
}
}


这里完成将Windsor和MS DI注册，统一转换为根节点的IServiceProvider，内部流程独立走Windsor，对外则是MS DI的流程。

IHostBuilder扩展方法

为了调用更简洁易懂，在IHostBuilder上扩展一个UseWindsorContainer方法.

public static IHostBuilder UseWindsorContainer(this IHostBuilder hostBuilder, TWindsorContainerModule containerModule)
where TWindsorContainerModule : class, IWindsorContainerModule
{
return hostBuilder
.UseServiceProviderFactory(new WindsorContainerFactory(containerModule))
.ConfigureServices(services =>
{
services.AddSingleton();
});
}


编写示例代码

internal class Sample : IWindsorContainerModule
{
public void Configure(WindsorContainer container)
{
Console.WriteLine("IWindsorContainerModule Instance Name:sample");
container.Register(Component.For(typeof(IHelloInterface)).ImplementedBy(typeof(HelloInterface)).LifestyleSingleton());
}
}
public interface IHelloInterface
{
void Show();
}
internal class HelloInterface : IHelloInterface
{
public void Show()
{
Console.WriteLine(nameof(HelloInterface));
}
}


修改Program.CreateHostBuilder

public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.UseWindsorContainer(new Sample()) //新增
.ConfigureWebHostDefaults(webBuilder =>
{
webBuilder
.UseStartup();
});


修改Controllers.WeatherForecastController.Get

public IEnumerable Get()
{
Console.WriteLine(_helloInterface.GetType().FullName); //打印接口实际实现，验证是否代理到Castle.Windsor
_helloInterface.Show(); //接口调用方法

var rng = new Random();
return Enumerable.Range(1, 5).Select(index => new WeatherForecast
{
Date = DateTime.Now.AddDays(index),
TemperatureC = rng.Next(-20, 55),
Summary = Summaries[rng.Next(Summaries.Length)]
})
.ToArray();
}


后记

感谢Lemon大人的指点~关于 IHostBuilder.UseServiceProviderFactory到IHostBuilder.ConfigureServices的细节和最初的预估差异不小，最早的代码实现版本是IHostBuilder.ConfigureServices内注册了IServiceProviderFactory，希望更优雅的实现替换DI容器，现实是这块是不可以的~

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