填充子节点列表：Linq 混淆和关注点分离
我正在尝试在我的应用程序中实现树视图。我正在使用 MVC2 Preview 1 和 SubSonic 3 SimpleRepository。我对 MVC 和 Linq 都是新手。
我的问题是，我不确定如何将子节点列表添加到我传递回视图的模型记录中。因此，我在我的模型类中添加了一个名为 Children 的 IEnumerable，我将其填充到控制器操作中：
public class Category
{
public Category()
{
}
public int ID { get; set; }
public int? ParentId { get; set; }
[Required(ErrorMessage="Name is required")]
public string Name { get; set; }
[SubSonicIgnore]
public IEnumerable<Category> Children { get; set; }
}
然后在控制器操作中，我提取所有记录并迭代更新 Children 成员：
public ActionResult Index()
{
var categories = _repo.All<Category>();
foreach (var c in categories)
{
c.Children = from p in _repo.All<Category>()
where p.ParentId == c.ID
orderby p.Name
select p;
}
return View(categories);
}
我的 2 个问题是 #1 为什么这不是工作？在循环范围之外，我的更改将丢失。 #2 从一般意义上来说，这是正确的方法吗？将此代码放入控制器感觉就像黑客。
I am trying to implement a tree view in my application. I am using MVC2 Preview 1, and SubSonic 3 SimpleRepository. I am new to both MVC and Linq.
My problem is that I am not sure how to add a list of child nodes to the model record that I am passing back to the View. So I have added a IEnumerable called Children to my model class that I populate in the controller action:
public class Category
{
public Category()
{
}
public int ID { get; set; }
public int? ParentId { get; set; }
[Required(ErrorMessage="Name is required")]
public string Name { get; set; }
[SubSonicIgnore]
public IEnumerable<Category> Children { get; set; }
}
Then in the controller action, I pull all of the records and iterate through updating the Children member:
public ActionResult Index()
{
var categories = _repo.All<Category>();
foreach (var c in categories)
{
c.Children = from p in _repo.All<Category>()
where p.ParentId == c.ID
orderby p.Name
select p;
}
return View(categories);
}
My 2 questions are #1 Why does this not work? Outside of the scope of the loop my changes are lost. #2 In a general sense, is this the right approach? Putting this code in the controller feels like a hack.
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至于为什么它不起作用，我怀疑延迟执行正在让你烦恼。如果像这样包装 Linq 查询
( from ... select p).ToList()，它将导致查询被评估。至于方法，它是表示层中的数据访问，所以一般来说，这是应该避免的。
As for why it doesn't work, I suspect deferred execution is getting you. If you wrap the Linq query like so
( from ... select p).ToList()it will cause the query to be evaluated.Regarding the approach, it is data access in the presentation tier, so generally speaking, that would be something to avoid.