c# - 通用存储库和自定义类型的实体 ID

Question

我有以下层次结构:

public interface IIdentifiable<TKey> where TKey : IEquatable<TKey>
{
     TKey Id { get; set; }
}

public interface IEntity<TKey> : IIdentifiable<TKey> where TKey : IEquatable<TKey>
{
}


//base entity
public class Entity<TKey> : IEntity<TKey> where TKey : IEquatable<TKey>
{
    public virtual TKey Id { get; set; }
}

public class Test1: Entity<long>
{
...
}

这是存储库:

public interface IRepository<T, TKey>
        where T : IEntity<TKey>
        where TKey : IEquatable<TKey>
    {
      ...
    }

这个通用存储库:

public class Repository<T, TKey> : IRepository<T, TKey>
        where T : IEntity<TKey>
        where TKey : IEquatable<TKey>
{
...
}

这是我的通用 api Controller :

public class BaseReadController<T, TKey> : ApiController where T : IEntity<TKey> where TKey : IEquatable<TKey>
    {
        private readonly IRepository<T, TKey> _repo;

        public BaseReadController(IRepository<T, TKey> repo)
        {
            _repo = repo;
        }      

        public SingleResult<T> Get([FromODataUri] TKey key)
        {
          var test = _repo.Query().Where(t => t.Id == key);
        }
    }

但是我得到 Cannot apply operator == to operands of type Tkey and TKey。

我试过这样的:

var test = _repo.Query().Where(t => t.Id.Equals(key))

但是我得到一个 NHibernate 异常:

message: "Boolean Equals(Int64)"
stacktrace: "   at NHibernate.Linq.Visitors.HqlGeneratorExpressionTreeVisitor.VisitMethodCallExpression(MethodCallExpression expression)
type: "System.NotSupportedException"

Answer 1

NHibernate 的 LINQ 提供程序有一些……需要改进的地方。因此我不建议尝试寻找一些方法来替换 .Query().Where(t => t.Id == key);用别的东西...

相反，我们应该扩展我们的 IRepository本地调用 session.Get<T>(key)

public interface IRepository<T, TKey>
    where T : IEntity<TKey>
    where TKey : IEquatable<TKey>
{
  ...
  Get<T>(TKey key)
}

实现方式如下:

public class Repository<T, TKey> : IRepository<T, TKey>
        where T : IEntity<TKey>
        where TKey : IEquatable<TKey>
{
...
    public virtual Get<T>(TKey key)
    {
        var session = ... // get current session
        var result = session.Get<T>(key);
        return result;
    }
}

最后在我们的 Controller 中:

public virtual T Get([FromODataUri] TKey key)
{
    var entity = _repo.Get<T>(key);
    return T;
}