LINQ 选择实体并将其转换为视图模型
本文关键字:转换 视图 模型 选择 实体 LINQ | 更新日期: 2023-09-27 18:34:02
我对Linq并不陌生,但由于任何原因我都无法解决这个问题。
假设我有以下模型。显然,这是示例模型。
public class Parent
{
public int Id { get; set; }
public List<Child> Children { get; set; }
public DateTime CreateDate { get; set; }
}
public class Child
{
public int Id { get; set; }
public List<Toys> Toys { get; set; }
public DateTime CreateDate { get; set; }
}
public class Toys
{
public string Id { get; set; }
public string Name { get; set; }
public DateTime CreateDate { get; set; }
}
我想要的是将它们转换为ViewModels。以下是我的视图模型是如何定义的
public class ParentViewModel
{
public int Id { get; set; }
public List<ChildViewModel> Children { get; set; }
}
public class ChildViewModel
{
public int Id { get; set; }
public List<ToysViewModel> Toys { get; set; }
}
public class ToysViewModel
{
public string Id { get; set; }
public string Name { get; set; }
}
我的问题
如何选择模型并将其转换为视图模型。这是我已经尝试过的。
var q = from p in dbContext.Parents
where p.Id = 123
select new ParentViewModel
{
Id = p.Id,
Children = ???
};
如何获得儿童及其玩具清单?
提前感谢!
如果在数据库中正确建模了关系,则
select new ParentViewModel
{
Id = p.Id,
Children = p.Children.Select(c => new ChildViewModel {
Id = c.Id,
Toys = c.Toys.Select(t => new ToyViewModel { ... }).ToList()
}).ToList()
};
为了清楚起见,我更愿意将其分解为这样的函数:
public static ParentViewModel AsViewModel(Parent parent)
{
var childViewModels = parent.Children.Select(AsViewModel).ToList();
return new ParentViewModel { Id = parent.Id, Children = childViewModels };
}
public static ChildViewModel AsViewModel(Child child)
{
var toyViewModels = child.Toys.Select(AsViewModel).ToList();
return new ChildViewModel { Id = child.Id, Toys = toyViewModels };
}
public static ToyViewModel AsViewModel(Toy toy)
{
return new ToyViewModel { Id = toy.Id, Name = toy.Name };
}
那么它可以像这样使用:
var q = dbContext.Parents.Where(p => p.Id == 123).Select(AsViewModel);
考虑使用一些自动映射工具,如Automampper。
定义某处映射:
Mapper.CreateMap<Parent, ParentViewModel>();
Mapper.CreateMap<Child, ChildViewModel>();
Mapper.CreateMap<Toys, ToysViewModel>();
和你的代码
Parent parent = GetParentById(123); // use LINQ to get parent
ParentViewModel pvm = Mapper.Map<ParentViewModel>(parent);
我会使用AutoMapper将我的实体转换为模型。它很好地支持集合。
你是这个意思吗?
var q = from p in dbContext.Parents
where p.Id = 123
select new ParentViewModel
{
Id = p.Id,
Children = p.Children.Select(c => new ChildViewModel
{
Id = c.Id,
Toys = c.Toys.Select(t => new ToysViewModel
{
Id = t.Id
}).ToList()
}).ToList()
};
要保持自己的写作风格:
var q = from p in dbContext.Parents
where p.Id == 123
select new ParentViewModel
{
Id = p.Id,
Children = (from c in p.Children
select new ChildViewModel()
{
Id = c.Id,
Toys = (from t in c.Toys
select new ToyViewModel()
{
Id = t.Id,
Name = t.Name
}).ToList()
}).ToList()
};
我会打电话给Toy
而不是Toys
,ToyViewModel
而不是ToysViewModel