Question

在使用我创建的界面时遇到麻烦。我尝试实现它，但是发生错误。任何答案表示赞赏。提前致谢。

这是我要实现的实际接口。

namespace CRDM.Core.Models
{
  [Table("cities")]
  public class City : ICity<CountryState>
  {
  }

  [Table("country_states")]
  public class CountryState : ICountryState<Country>
  {        
  }

  [Table("countries")]
  public class Country : ICountry
  {       
  }
}

namespace CRDM.Core.Abstractions.Entities
{
 public interface ICity <TState> :
    where TState : ICountryState<ICountry>
 {
    TState StateReference { get; set; }
 }

 public interface ICountryState<TCountry> :
    where TCountry : ICountry
 {

 }

 public interface ICountry
 {
 }
}

我成功实现了Country和CountryState类，但是实现City时出错。错误消息在这里。

类型CRDM.Core.Models.CountryState不能用作类型   通用类型或方法TState中的参数ICity<TState>。

没有来自的隐式引用转换   CRDM.Core.Models.CountryState至   CRDM.Core.Abstractions.Entities.ICountryState<CRDM.Core.Abstractions.Entities.ICountry>。

Answer 1

尝试通过这种方式进行操作：

namespace CRDM.Core.Models
{

    public class City : ICity<CountryState,Country>
    {
        public CountryState StateReference { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
    }


    public class CountryState : ICountryState<Country>
    {
    }


    public class Country : ICountry
    {
    }
}

namespace CRDM.Core.Abstractions.Entities
{
    public interface ICity<TState,TCountry>        
       where TCountry: ICountry
       where TState : ICountryState<TCountry>
    {
        TState StateReference { get; set; }
    }

    public interface ICountryState<TCountry>        
       where TCountry : ICountry
    {

    }

    public interface ICountry
    {
    }
}

或者这样：

    namespace CRDM.Core.Models
    {
        public class City : ICity<CountryState>
        {
            public CountryState StateReference { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
        }

        public class CountryState : ICountryState<ICountry>
        {
        }

        public class Country : ICountry
        {
        }
    }

    namespace CRDM.Core.Abstractions.Entities
    {
        public interface ICity<TState> 

           where TState : ICountryState<ICountry>
        {
            TState StateReference { get; set; }
        }

        public interface ICountryState<TCountry> 

           where TCountry : ICountry
        {

        }

        public interface ICountry
        {
        }
    }

Answer 2

您可能需要问自己，您要达到什么目标，是否只是使事情变得比原来复杂得多。如果您想使用接口访问这些实体，但使它们与实体框架一起使用，我会...

namespace CRDM.Core.Models
{
    using CRDM.Core.Abstractions.Entities;

    [Table("cities")]
    public class City : ICity
    {
        public CountryState StateReference { get; set; }
        ICountryState ICity.StateReference
        {
            get
            {
                return StateReference;
            }
            set
            {
                StateReference = (CountryState)value;
            }
        }
    }

    [Table("country_states")]
    public class CountryState : ICountryState
    {
        public Country Country { get; set; }
        ICountry ICountryState.Country
        {
            get
            {
                return Country;
            }
            set
            {
                Country = (Country)value;
            }
        }
    }

    [Table("countries")]
    public class Country : ICountry
    {
    }
}

namespace CRDM.Core.Abstractions.Entities
{
    public interface ICity
    {
        ICountryState StateReference { get; set; }
    }

    public interface ICountryState
    {
        ICountry Country { get; set; }
    }

    public interface ICountry
    {
    }
}

如何与通用对象一起使用接口？

2 个答案: