Question

我是LINQ的新手，所以显然在编写查询方面遇到了困难。

这是我的代码：

public class Customer
{
    public int cid { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string City { get; set; }
}

public class Order
{
    public int Orderid { get; set; }
    public int customerid { get; set; }
    public int Quantity { get; set; }
}

static void Main(string[] args)
{
    List<Customer> customerList = new List<Customer>
    {
        new Customer(){cid=1,FirstName="Avinash",LastName="Kothamasu",City="Chennai"},
        new Customer(){cid=2,FirstName="Abhiram",LastName="Kumar",City="Chennai"},
        new Customer{cid=3,FirstName="Balu",LastName="Chinna",City="Chennai"},
        new Customer{cid=4,FirstName="Sai",LastName="Kothamasu",City="Bhimavaram"},
        new Customer{cid=5,FirstName="Harshita",LastName="Kothamasu",City="Bhimarvarm"},
        new Customer{cid=6,FirstName="Mounika",LastName="Kothamasu",City="Guntur"}
    };

    List<Order> orderList = new List<Order>
    {
        new Order(){Orderid=11,customerid=1,Quantity=20},
        new Order(){Orderid=111,customerid=1,Quantity=10},
        new Order(){Orderid=22,customerid=2,Quantity=15},
        new Order(){Orderid=222,customerid=2,Quantity=8},
        new Order(){Orderid=22222,customerid=2,Quantity=50},
        new Order(){Orderid=33,customerid=3,Quantity=10},
        new Order(){Orderid=333,customerid=3,Quantity=5},
        new Order(){Orderid=44,customerid=4,Quantity=4},
        new Order(){Orderid=55,customerid=5,Quantity=1},
        new Order(){Orderid=66,customerid=6,Quantity=2}
    };

    var OrderListforCustomers = from c in customerList
                                join o in orderList on
                                c.cid equals o.customerid
                                where o.Quantity > 1 && o.Quantity <= 50
                                group new { c, o } by new { o.customerid, c.FirstName, c.LastName, c.City } into customergroups
                                orderby customergroups.Key.customerid
                                select new
                                {
                                    CustomerID = customergroups.Key.customerid,
                                    CustomerName = customergroups.Key.FirstName.ToUpper() + " , " + customergroups.Key.LastName.ToUpper(),
                                    City = customergroups.Key.City,
                                    MaximumQuantityCount = customergroups.Select(x=>x.o).Max(x=>x.Quantity),
                                                *OrderIDwithMaxQuanCount=customergroups.Select(x=>x.o.Orderid).Where();*
                                };

    Console.Write("CID" + " || ");
    Console.Write("CustomerName" + " || ");
    Console.Write("City" + " | ");
    Console.Write("MaximumQuantityCount" + " || ");
    Console.Write("OrderIDwithMaxCount");
    Console.WriteLine(Environment.NewLine);

    foreach (var custgroup in OrderListforCustomers)
    {
        Console.Write(custgroup.CustomerID + " || ");
        Console.Write(custgroup.CustomerName + " || ");
        Console.Write(custgroup.City + " || ");
        Console.Write(custgroup.MaximumQuantityCount + " || ");
        Console.Write(Environment.NewLine);
        Console.ReadLine();

在这里，我要做的是打印客户详细信息以及订单详细信息和一些条件。

我需要打印具有最大数量的客户的订单

我能够为特定客户提供MaxOrderCount，但无法获取具有最大数量的订单ID

在查询中，select子句中的最后一行，我在如何编写

方面遇到了一些困难

请帮助..

Answer 1

您可以先订购，然后选择如下：

 OrderIDwithMaxQuanCount=customergroups.OrderByDescending(x => x.o.Quantity)
                                       .Select(x => x.o.Orderid).FirstOrDefault()

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