【高分在线急等】LINQ查询问题，代码已贴出
-----------------Sqlserver表数据Category--------------------------
表结构：
ID Category
1 分类1
2 分类2
3 分类3
4 分类4
5 分类5

-----------------Sqlserver表数据Detail--------------------------
表结构：
ID CategoryID Name
1 1 子类1
2 1 子类2

3 2 子类3
4 2 子类3
5 2 子类3

--------------需用Linq查出结果----------------------------------

[{"CategoryName":"分类1",
"DetailCount":2,
Items:[{"ItemName":"子类1",Count:1}
{"ItemName":"子类2",Count:1}]
}
{"CategoryName":"分类2",
"DetailCount":3,
Items:[{"ItemName":"子类3",Count:3}]
}
]

-------------已建立的实体类-------------------------------------
class Category
//大类名称
public string CategoryName;
//下面子类总数
public int DetailCount;
//子类list
public List<Detail> item;

class Detail
//子类名称
public string ItemName;
//子类个数
public int Count;


LINQ 类
[解决办法]
var query = from c in Category
join d into Detail

on c.id equals d.CategoryID into g
select new { CategoryName = c.Category, DetailCount = g.Count(), Items = g };
[解决办法]

    class Program
    {
        static void Main(string[] args)
        {
            List<Category> categorys = new List<Category>
                                      {
                                            new Category {Id=1,Name="分类1"},
                                            new Category {Id=2,Name="分类2"},
                                            new Category {Id=3,Name="分类3"},
                                            new Category {Id=4,Name="分类4"},
                                            new Category {Id=5,Name="分类5"},
                                      };
            List<Detail> details = new List<Detail>
                                       { 
 
                                           new Detail{Id=1,CategoryId=1,Name="子类1-1"},
                                           new Detail{Id=2,CategoryId=1,Name="子类1-2"},
                                           new Detail{Id=3,CategoryId=2,Name="子类2-1"},
                                           new Detail{Id=4,CategoryId=2,Name="子类2-2"},
                                           new Detail{Id=5,CategoryId=3,Name="子类3-1"},
                                           new Detail{Id=6,CategoryId=3,Name="子类3-2"},
                                           new Detail{Id=7,CategoryId=3,Name="子类3-3"},
                                       };


            var query = details.GroupBy(g => new { g.CategoryId }).Select(s => new Result
                                                                                   { 
 
                                                                                       CategoryName = categorys.FirstOrDefault(f => f.Id == s.Key.CategoryId).Name,
                                                                                       DetailCount = details.Where(w => w.CategoryId == s.Key.CategoryId).Count(),
                                                                                       Items = details.Where(w => w.CategoryId == s.Key.CategoryId).ToList()
                                                                                   });

        }
    }


    public class Result
    {
        public string CategoryName { get; set; }
        public Int32 DetailCount { get; set; }
        public List<Detail> Items { get; set; }
    }

    public class Category 
 
    {
        public Int32 Id { get; set; }
        public string Name { get; set; }

    }
    public class Detail
    {
        public Int32 Id { get; set; }
        public Int32 CategoryId { get; set; }
        public string Name { get; set; }
    }