.NET 6 Web API依赖注入报错：部分服务无法构造问题排查

问题背景 #

从.NET 5迁移到.NET 6最小宿主模型后，原本运行正常的服务依赖注入逻辑触发服务构造失败错误，.NET 5环境下基于Startup类的注册流程无异常。

相关代码 #

初始Program.cs代码 #

using NSBSL.WebAPI.API;

var builder = WebApplication.CreateBuilder(args);

// 注册控制器服务
builder.Services.AddControllers();
// Swagger/OpenAPI相关配置
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();
builder.Services.RegisterServices();
builder.Configuration.AddJsonFile("appsettings.json", false, false).AddJsonFile($"appsettings.{Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT")}.json", true);

var app = builder.Build();

// 配置HTTP请求管道
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();
app.UseAuthorization();
app.MapControllers();
app.Run();

服务注册扩展及工厂类代码 #

• 服务扩展类

public static class ServiceExtensions
{
    public static void RegisterServices(this IServiceCollection services)
    {
        new LogicFactory().ConfigureServices(services);
    }
}

• LogicFactory类

public class LogicFactory : IInjectionFactory
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddSingleton<ISpeedPatternLogic, SpeedPatternLogic>();
        new DatasourceFactory().ConfigureServices(services);
    }
}

• DatasourceFactory类

public class DatasourceFactory : IInjectionFactory
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddSingleton<ISpeedPatternDatasource, SpeedPatternDatasource>();
    }
}

• 框架通用IInjectionFactory接口定义

public interface IInjectionFactory
{
    void ConfigureServices(IServiceCollection services);
}

报错堆栈 #

at Microsoft.Extensions.DependencyInjection.ServiceProvider..ctor(ICollection`1 serviceDescriptors, ServiceProviderOptions options)
at Microsoft.Extensions.DependencyInjection.ServiceCollectionContainerBuilderExtensions.BuildServiceProvider(IServiceCollection services, ServiceProviderOptions options)
at Microsoft.Extensions.DependencyInjection.DefaultServiceProviderFactory.CreateServiceProvider(IServiceCollection containerBuilder)
at Microsoft.Extensions.Hosting.Internal.ServiceFactoryAdapter`1.CreateServiceProvider(Object containerBuilder)
at Microsoft.Extensions.Hosting.HostBuilder.CreateServiceProvider()
at Microsoft.Extensions.Hosting.HostBuilder.Build()
at Microsoft.AspNetCore.Builder.WebApplicationBuilder.Build()
at Program.<Main>$(String[] args) 

排查过程 #

• 首次尝试：直接在Program.cs中将ISpeedPatternLogic的注册生命周期改为Transient，仍触发相同报错，测试代码如下：

using NSBSL.WebAPI.BusinessLogic.Interfaces.SpeedPattern;
using NSBSL.WebAPI.BusinessLogic.Services.SpeedPattern;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddControllers();
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();
builder.Services.AddTransient<ISpeedPatternLogic, SpeedPatternLogic>();

• 二次排查：核对业务接口与实现类的定义，代码如下：
  • ISpeedPatternLogic接口

  public interface ISpeedPatternLogic : ILoadable<SpeedPatternModel>
  {
  }
  

  • ILoadable接口

  public interface ILoadable<T> : ILogicBase<T> where T : IModelBase
  {
      Task LoadAsync(CancellationToken token);
  }
  

  • SpeedPatternLogic实现类

  public class SpeedPatternLogic : ServicesBase<SpeedPatternModel>, ISpeedPatternLogic
  {
      private readonly ISpeedPatternDatasource _speedPatternDatasource;
      public SpeedPatternLogic(INSBSLConfiguration configuration, IMapper mapper, ISpeedPatternDatasource speedPatternDatasource) : base(configuration, mapper)
      {
          _speedPatternDatasource = speedPatternDatasource;
      }
  
      public async override Task<IEnumerable<SpeedPatternModel>> GetAllAsync(CancellationToken token)
      {
          return Mapper.Map<IEnumerable<SpeedPatternModel>>(await _speedPatternDatasource.GetAllAsync(token));
      }
  
      public Task LoadAsync(CancellationToken token)
      {
          throw new NotImplementedException();
      }
  }
  

根因定位 #

查看SpeedPatternLogic的构造函数，共依赖三个服务：INSBSLConfiguration、IMapper、ISpeedPatternDatasource。其中ISpeedPatternDatasource已在DatasourceFactory中完成注册，但框架内置的INSBSLConfiguration服务注册逻辑被遗漏。
框架中原本通过NSBSLConfigurationFactory完成该服务的注册：

public class NSBSLConfigurationFactory : IInjectionFactory
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.TryAddSingleton<INSBSLConfiguration, NSBSLConfiguration>();
    }
}

.NET 5版本下，所有微服务继承的ApiStartup基类会自动调用以下方法完成该配置服务的注册：

private void RegisterNSBSLConfigurationInterfaces(IServiceCollection services)
{
    new NSBSLConfigurationFactory().ConfigureServices(services);
}

迁移到.NET 6最小宿主模型后，原Startup基类的自动执行逻辑失效，未手动调用该注册方法，导致DI容器中缺失INSBSLConfiguration服务实例，容器构建时校验服务依赖链失败，抛出构造异常。

修复方案 #

在Program.cs的服务注册阶段，补充调用NSBSLConfigurationFactory的注册方法，将INSBSLConfiguration注入DI容器即可：

// 补充注册框架配置服务
new NSBSLConfigurationFactory().ConfigureServices(builder.Services);
builder.Services.RegisterServices();

内容的提问来源于stack exchange，提问作者user3263515