Sí!
Debería estar anulando Equals
y GetHashCode
. Pero, usted no debería estar haciendo igualdad de valor (Name == other.Name && Age == other.Age
), ¡debería estar haciendo la igualdad de identidad!
Si no lo hace, lo más probable es que se encuentre con la comparación de un proxy de una entidad con la entidad real y será miserable para depurar. Por ejemplo:
public class Blog : EntityBase<Blog>
{
public virtual string Name { get; set; }
// This would be configured to lazy-load.
public virtual IList<Post> Posts { get; protected set; }
public Blog()
{
Posts = new List<Post>();
}
public virtual Post AddPost(string title, string body)
{
var post = new Post() { Title = title, Body = body, Blog = this };
Posts.Add(post);
return post;
}
}
public class Post : EntityBase<Post>
{
public virtual string Title { get; set; }
public virtual string Body { get; set; }
public virtual Blog Blog { get; set; }
public virtual bool Remove()
{
return Blog.Posts.Remove(this);
}
}
void Main(string[] args)
{
var post = session.Load<Post>(postId);
// If we didn't override Equals, the comparisons for
// "Blog.Posts.Remove(this)" would all fail because of reference equality.
// We'd end up be comparing "this" typeof(Post) with a collection of
// typeof(PostProxy)!
post.Remove();
// If we *didn't* override Equals and *just* did
// "post.Blog.Posts.Remove(post)", it'd work because we'd be comparing
// typeof(PostProxy) with a collection of typeof(PostProxy) (reference
// equality would pass!).
}
Aquí es un ejemplo de clase base si está utilizando int
como su Id
(que también podría ser abstraído a any identity type):
public abstract class EntityBase<T>
where T : EntityBase<T>
{
public virtual int Id { get; protected set; }
protected bool IsTransient { get { return Id == 0; } }
public override bool Equals(object obj)
{
return EntityEquals(obj as EntityBase<T>);
}
protected bool EntityEquals(EntityBase<T> other)
{
if (other == null)
{
return false;
}
// One entity is transient and the other is not.
else if (IsTransient^other.IsTransient)
{
return false;
}
// Both entities are not saved.
else if (IsTransient && other.IsTransient)
{
return ReferenceEquals(this, other);
}
else
{
// Compare transient instances.
return Id == other.Id;
}
}
// The hash code is cached because a requirement of a hash code is that
// it does not change once calculated. For example, if this entity was
// added to a hashed collection when transient and then saved, we need
// the same hash code or else it could get lost because it would no
// longer live in the same bin.
private int? cachedHashCode;
public override int GetHashCode()
{
if (cachedHashCode.HasValue) return cachedHashCode.Value;
cachedHashCode = IsTransient ? base.GetHashCode() : Id.GetHashCode();
return cachedHashCode.Value;
}
// Maintain equality operator semantics for entities.
public static bool operator ==(EntityBase<T> x, EntityBase<T> y)
{
// By default, == and Equals compares references. In order to
// maintain these semantics with entities, we need to compare by
// identity value. The Equals(x, y) override is used to guard
// against null values; it then calls EntityEquals().
return Object.Equals(x, y);
}
// Maintain inequality operator semantics for entities.
public static bool operator !=(EntityBase<T> x, EntityBase<T> y)
{
return !(x == y);
}
}
Por favor marque la respuesta SÍ como la respuesta correcta . –