我有三个小表,如下所示：

现在我想得到一些关于每个房间每天订购多少餐食的报告.

我在CafeteriaClients表中有ROOM属性(名为AULA).

我想列出每个ROOM订购了多少OrderedItems.如果在该ROOM中订购了MenuType == EXTRA的OrderedItems,则列出所有订购它的客户(姓名姓氏).像这样的东西：

ROOM 1
          PASTA: 12
          STEAK: 13
          SALAD: 12
           EXTRAS:
             TIRAMISU: 12
                 UserName 1
                 UserName 2
                 ....
                 UserName 12
             MACEDONIA: 2
                 UserName 3
                 UserName 4
 ROOM 2
          .....
          ......

到目前为止我所做的是：

    [HttpGet]
    public IHttpActionResult GetOrdersForRooms()
    {
        using (var ctx = new CafeteriaContext())
        {
            var Date = DateTime.Today;

            var orders = ctx.CafOrders.Where(d => d.Date == Date)
                .SelectMany(o => o.OrderedItems
                .Select(c => new { 
                            Room = c.CafClient.AULA, 
                            MealItem = c.Name, 
                            Type = c.MenuType, 
                            ClientName = c.CafClient.Name }))
                 .ToList();



            return Ok(orders);
        }           
    }

这给我带来了以下形式的结果,这是好的,但我确信LINQ还有更多,并且必须有一种方法可以更好地使用我没有找到的SelectMany或GroupBy.现在我必须查看列表,读取每个对象的属性,并按ROOMS和EXTRAS等排列它们.

    {
      "Room": "Aula 2",
      "MealItem": "Pizza Italiana",
      "Type": "EXTRA",
      "ClientName": "Riki Gervais"
    }, 
    {
      "Room": "Aula 3",
      "MealItem": "Spaghetti",
      "Type": "EXTRA",
      "ClientName": "John M Meyer"
    },
    {
      "Room": "Aula 3",
      "MealItem": "Sausage",
      "Type": "INTERNAL",
      "ClientName": "Steve O'Dwayer"
  },
  {
      "Room": "Aula 3",
      "MealItem": "Pasta",
      "Type": "EXTRA",
      "ClientName": "Allan Parker"
  },
  {
      "Room": "Aula 6",
      "MealItem": "Riggatoni",
      "Type": "EXTERNAL",
      "ClientName": "John Susack"
  }

然后我过滤这些结果并以所需的形式排列它们但我想知道是否可以从一开始就使用LINQ to Entities做更多的事情并获得没有冗余的信息.例如,每个ROOMS直接对结果进行分组.

    [Table("CafOrders")]
public class CafOrders
{
    [Key]
    [Required]
    public int Id { get; set; }

    [Required]
    public DateTime Date { get; set; }

    public string Note { get; set; }

    public decimal Total { get; set; }

    public int ClientId { get; set; }

    [ForeignKey("ClientId")]
    public CafeteriaClients CafeteriaClient { get; set; }

    public ICollection<OrderedItems> OrderedItems { get; set; }

}



   [Table("CafeteriaClients")]
public class CafeteriaClients
{
    [Key]
    [Required]
    public int Id { get; set; }

    [Required]
    public string Name { get; set; }

    [Required]
    public string Surname { get; set; }

    public string AULA { get; set; }

    public string MATR { get; set; }

    [Required]
    public string CustomerType { get; set; }

    public string GRUPPO { get; set; }


    public ICollection<OrderedItems> OrderedItems { get; set; }
}




    public class OrderedItems
{

    public int Id { get; set; }

    public int OrderId { get; set; }

    public int ClientId { get; set; }

    public string Name { get; set; }

    public decimal Price { get; set; }

    public string Description { get; set; }

    public string MenuType { get; set; }

    [ForeignKey("OrderId")]
    public CafOrders CafOrder { get; set; }

    [ForeignKey("ClientId")]
    public CafeteriaClients CafClient { get; set; }

}

最佳答案 创建一个你想要的类模式

    public class Room
    {
        public string Name { get; set; }

        public List<Meal> Meals { get; set; }
    }

    public class Meal
    {
        public string Name { get; set; }
        public int Count { get; set; }

        public List<EXTRA> Extras { get; set; }
     }

    public class EXTRA
    {
        public string Name { get; set; }

        public List<User> UserNames { get; set; }
    }

    public class User
    {
        public string Name { get; set; }

        public int Count { get; set; }
    }

然后尝试这个……

  var groupOrders = CafOrders.GroupBy(x => x.CafeteriaClient.AULA)
        .Select(x => new Room
         {
             Name = x.Key,
             Meals = x.SelectMany(y => y.OrderedItems)
                      .GroupBy(y => y.Name)
                      .Select(z => new Meal
         {
           Name = z.Key,
           Count = z.Count(),
           Extras = z.Where(t => t.MenuType == "EXTRA")
                     .GroupBy(t => t.Name)
                     .Select(t => new EXTRA
         {
            Name = t.Key,
            UserNames = t.GroupBy(k => new { k.CafClient.Name, 
                                             k.CafClient.Surname 
            })
            .Select(k => new User {
            Name = k.Key.Name + k.Key.Surname, 
             Count = k.Count() }).ToList()
            }).ToList()
           }).ToList()
         });

更新

  public class Meal
  {
        public string Name { get; set; }
        public int Count { get; set; }
  }

 public class Room
 {
        public string Name { get; set; }

        public List<Meal> Meals { get; set; }

        public List<EXTRA> Extras { get; set; }

  }

   var groupOrders = CafOrders.GroupBy(x => x.CafeteriaClient.AULA)
        .Select(x => new Room
         {
             Name = x.Key,
             Meals = x.SelectMany(y => y.OrderedItems)
                      .Where(y => y.MenuType != "EXTRA")
                      .GroupBy(y => y.Name)
                      .Select(z => new Meal
                       {
                           Name = z.Key,
                           Count = z.Count()
                       }).ToList(),
             Extras = x.SelectMany(y => y.OrderedItems)
                      .Where(y => y.MenuType == "EXTRA")
                      .GroupBy(y => y.Name)
                      .Select(z => new EXTRA
                      {
                          Name = z.Key,
                          Count = z.Count(),
                          UserNames = z.GroupBy(k => new { k.CafClient.Name, 
                                                           k.CafClient.Surname })
                                       .Select(k => new User {
                                           Count = k.Count(), 
                                           Name = k.Key.Name + k.Key.Surname })
                                         .ToList()

                      }).ToList()
         });