ASP.NET Core 7 Web API中Program.cs注册双服务遇循环依赖错误

从错误信息可以明确看出，CustomerCommandRepository的构造函数中注入了ICustomerCommandRepository本身，导致了自循环依赖：

ModiranKhodro.Core.Contracts.Customers.Commands.ICustomerCommandRepository(CustomerCommandRepository) -> ICustomerCommandRepository

解决步骤： #

1. 检查并修正CustomerCommandRepository的构造函数
   打开CustomerCommandRepository的实现代码，找到构造函数，移除对ICustomerCommandRepository的注入。正常情况下，仓储类应该依赖数据库上下文（比如DbContext）、查询仓储（ICustomerQueryRepository）或其他基础服务，而非自身的接口。

   错误示例（导致循环）：

   public class CustomerCommandRepository : ICustomerCommandRepository
   {
       private readonly ICustomerCommandRepository _customerCommandRepo;
   
       // 错误：注入了自身接口
       public CustomerCommandRepository(ICustomerCommandRepository customerCommandRepo)
       {
           _customerCommandRepo = customerCommandRepo;
       }
   }
   

   修正后的示例（注入正确依赖）：

   public class CustomerCommandRepository : ICustomerCommandRepository
   {
       private readonly AppDbContext _dbContext;
       private readonly ICustomerQueryRepository _customerQueryRepo;
   
       public CustomerCommandRepository(AppDbContext dbContext, ICustomerQueryRepository customerQueryRepo)
       {
           _dbContext = dbContext;
           _customerQueryRepo = customerQueryRepo;
       }
   
       // 实现ICustomerCommandRepository的方法
   }
   

2. 重新验证服务注册
   你的现有注册代码本身无问题：

   builder.Services.AddScoped<ICustomerQueryRepository, CustomerQueryRepository>();
   builder.Services.AddScoped<ICustomerCommandRepository, CustomerCommandRepository>();
   

   只要修复CustomerCommandRepository的构造函数，该注册逻辑就能正常运行，MediatR的Handler依赖问题也会随之解决。

3. 极端情况的临时方案（不推荐）
   如果因特殊设计需求必须保留类似依赖（非常罕见），可通过IServiceProvider延迟获取服务规避循环：

   public class CustomerCommandRepository : ICustomerCommandRepository
   {
       private readonly IServiceProvider _serviceProvider;
       private ICustomerCommandRepository? _customerCommandRepo;
   
       public CustomerCommandRepository(IServiceProvider serviceProvider)
       {
           _serviceProvider = serviceProvider;
       }
   
       private ICustomerCommandRepository CustomerCommandRepo => 
           _customerCommandRepo ??= _serviceProvider.GetRequiredService<ICustomerCommandRepository>();
   
       // 使用CustomerCommandRepo的方法
   }
   

   注意：这种方式会掩盖设计缺陷，优先推荐修复构造函数的依赖逻辑。

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