ASP.NET Core 3.1集成Identity后报错无法解析AutoMapper.IConfiguration服务

System.AggregateException: 'Some services are not able to be constructed (Error while validating the service descriptor 'ServiceType: Services.Contracts.IServiceManager Lifetime: Scoped ImplementationType: Service.ServiceManager': Unable to resolve service for type 'AutoMapper.Configuration.IConfiguration' while attempting to activate 'Service.ServiceManager'.)'
InvalidOperationException: Unable to resolve service for type 'AutoMapper.Configuration.IConfiguration' while attempting to activate 'Service.ServiceManager'.

报错本质是ASP.NET Core依赖注入容器无法为Service.ServiceManager类提供它构造函数声明需要的AutoMapper.Configuration.IConfiguration实例，常见触发原因有两个：

1. 命名空间引用错误：将ASP.NET Core自带的配置接口Microsoft.Extensions.Configuration.IConfiguration和AutoMapper的配置接口AutoMapper.Configuration.IConfiguration混淆，在ServiceManager构造函数中错误引用了AutoMapper的IConfiguration
2. AutoMapper服务未正确注册：确实需要使用AutoMapper配置能力，但未将AutoMapper相关服务注入到DI容器中

• 优先检查ServiceManager类的构造函数的IConfiguration引用命名空间：如果你的需求是注入项目全局配置（比如appsettings.json中的配置项），将引用改为using Microsoft.Extensions.Configuration;，删除using AutoMapper.Configuration;即可解决90%以上的该类报错
• 如果确实需要在ServiceManager中使用AutoMapper的配置能力，先确保已安装AutoMapper.Extensions.Microsoft.DependencyInjectionNuGet包，再在Startup.cs的ConfigureServices方法中添加AutoMapper服务注册：

  // 参数替换为你存放AutoMapper Profile配置类的程序集即可
  services.AddAutoMapper(AppDomain.CurrentDomain.GetAssemblies());
  

• 推荐ServiceManager中如果需要使用AutoMapper的映射能力，直接注入IMapper接口而非AutoMapper的配置类，构造函数示例：

  public ServiceManager(IRepositoryManager repositoryManager, IMapper mapper, Microsoft.Extensions.Configuration.IConfiguration configuration)
  {
      // 初始化逻辑
  }
  

• 如果你是在集成Identity过程中出现的该报错，检查服务注册顺序：将AutoMapper的注册逻辑放在Identity服务注册逻辑之前，避免注入覆盖

内容的提问来源于stack exchange，提问作者itz4blitz