与linq分组

Question

class Customer
{
    public string ID { get; set; }
    public string Name { get; set; }
    public List<Order> OrderList { get; set; }
}

class Order
{
    public string OrderNumber { get; set; }
    public List<Item> ItemList { get; set; }
}

class Item
{
    public string ItemName { get; set; }
}


    static void Main(string[] args)
    {

        System.Data.DataTable dt = new System.Data.DataTable();
        dt.Columns.Add("CustID");
        dt.Columns.Add("Name");
        dt.Columns.Add("OrderNumber");
        dt.Columns.Add("ItemName");

        dt.Rows.Add("1", "A", "O1", "Item1");
        dt.Rows.Add("1", "A", "O1", "Item2");
        dt.Rows.Add("1", "A", "O1", "Item3");

        dt.Rows.Add("1", "A", "O2", "Item4");
        dt.Rows.Add("1", "A", "O2", "Item5");

        dt.Rows.Add("1", "A", "O3", "Item1");

        dt.Rows.Add("2", "B", "O4", "Item1");
        dt.Rows.Add("2", "B", "O4", "Item2");

        dt.Rows.Add("2", "B", "O5", "Item3");


        dt.AcceptChanges();

        List<DataRow> dList = dt.AsEnumerable().ToList();


        //This is not working
        var qry = dList.GroupBy(x => x["CustID"])
                        .Select(g => new Customer
                        {
                            ID = g.Key.ToString(),
                            Name = g.First()["Name"].ToString(),
                            OrderList = g.GroupBy(t=> t["OrderNumber"]).Select(x => new Order
                            {

                                OrderNumber = x.First()["OrderNumber"].ToString(),
                                ItemList = g.GroupBy(u => u["OrderNumber"]).Select(y => new Item { ItemName = y.First()["ItemName"].ToString() }).ToList()
                            }).ToList()
                        }).ToList();
    }

我正在努力获得像这样的输出

Custtomer.Name="A"
Customer.ID="1"
Customer.OrderList = ListOfOrders with "01", "02", "03"
Customer.OrderList[0].ItemList = ListOfItems with that order Item1, Item2, Item3


Custtomer.Name="B"
Customer.ID="2"
Customer.OrderList = ListOfOrders with "04", "05"
Customer.OrderList[0].ItemList = ListOfItems with that order Item4, Item5

有人可以告诉我，我的qry有什么不对吗？

Answer 1

是的，您正试图在x电话中使用Select，但这超出了范围。此外，您尝试直接使用Name，但它不是分组键的一部分。最后，您尝试在Select中选择一个订单，而不是一组订单。我想你想要这个：

var qry = dList.GroupBy(x => new { CustID = (string) x["CustID"],
                                   Name = (string) x["Name"] })
               .Select(g => new Customer {
                          ID = g.Key.CustID,
                          Name = g.Key.Name,
                          OrderList = g.Select(x => new Order {
                                 // Indentation bad to avoid scrolling!
                                 OrderNumber = (string) x["OrderNumber"] })
                                       .ToList()
                       })
               .ToList();

假设CustID是唯一的（因此您每次都会获得相同的名称），您可以按照CustID进行分组，然后按照Achim的回答将第一个客户作为名称 - 但我个人更喜欢将所有“每个客户“密钥中的数据，因为逻辑上您正在分组的内容。

编辑：要回答已修改的问题，可以填充OrderList属性，如下所示：

OrderList = g.GroupBy(t=> (string) t["OrderNumber"]).Select(x => new Order
{
    OrderNumber = x.Key,
    ItemList = x.Select(y => new Item { 
                              ItemName = (string) y["ItemName"]
                        }).ToList()
}).ToList()

...但说实话，到那时它变得非常混乱。

Answer 2

var qry = dList.GroupBy(x => x["CustID"]).Select(g => new Customer
        {
            ID = g.Key.ToString(),
            Name = g.First()["Name"],
            OrderList=g.Select(o => new List<Order>(new Order{ OrderNumber=o["OrderNumber"]}))
        }).ToList();