linq - EF Core 中孙子属性的 Include 与 thenInclude

Question

加载孙子属性时是否首选这些方法之一？我喜欢第一个的简洁性，但我不知道它是否更昂贵。

return source
    .Include(x => x.Server)
    .Include(x => x.Server.User)
    .Include(x => x.Server.ParentServer)
    .Include(x => x.Server.DataCenter);

或

return source
    .Include(x => x.Server)
        .ThenInclude(s => s.User)
    .Include(x => x.Server)
        .ThenInclude(s => s.ParentServer)
    .Include(x => x.Server)
        .ThenInclude(s => s.DataCenter);

Answer 1

它们是等价的。第一个显然是首选，但对于集合导航来说这是不可能的。因此，ThenInclude()。

// Won't compile
return source
    .Include(x => x.Posts.Authors)
    .Include(x => x.Posts.Comments);

// Compiles
return source
    .Include(x => x.Posts)
        .ThenInclude(x => x.Authors)
    .Include(x => x.Posts)
        .ThenInclude(x => x.Comments);

但是，如果您想放弃编译时类型安全，也可以只使用字符串重载。

// Compiles, may throw
return source
    .Include("Posts.Authors")
    .Include("Posts.Comments");

但是请不要这样做......

// Over-thinking it ;-)
return source
    .Include(nameof(Blog.Posts) + "." + nameof(Post.Authors))
    .Include(nameof(Blog.Posts) + "." + nameof(Post.Comments));