获取最新日期的最新记录和组 - LINQ

Question

我有Capsule::getQueryLog()表格，如下所示

Billing

如您所见，AccoundID | Group | DateOfBill 1234 | A | 2017-07-12 1234 | B | 2017-07-16 1234 | C | 2017-07-31 1235 | A | 2017-07-31 1236 | B | 2017-07-31 1234在2017年7月进行了3次交易。所以我需要一个AccountID 1234必须在AccountID C的列表，因为那是最新日期事务。

这是我的代码段

Group

但结果是错误的。怎么做LINQ？

Answer 1

class Program
{
    static void Main(string[] args)
    {
        List<Billing> Billings = new List<Billing>()
        {
            new Billing()
            {
                AccountID = 1234, DateOfBill = new DateTime(2017,07,12), Group = "A"

            },
            new Billing()
            {
                AccountID = 1234, DateOfBill = new DateTime(2017,07,16), Group = "B"

            },
            new Billing()
            {
                AccountID = 1234, DateOfBill = new DateTime(2017,07,31), Group = "C"

            },
            new Billing()
            {
                AccountID = 1235, DateOfBill = new DateTime(2017,07,31), Group = "A"

            },
            new Billing()
            {
                AccountID = 1236, DateOfBill = new DateTime(2017,07,31), Group = "B"

            }               
        };

        var LatestAccount = from n in Billings
                            where (n.Group == "A" || n.Group == "B" || n.Group == "C")
                            group n by new { n.AccountID } into g
                            select g.Where(d => d.DateOfBill == g.Max(m => m.DateOfBill)).Select(x => new { AccountId = g.Key.AccountID, Group = x.Group, DateOfBill = x.DateOfBill }).FirstOrDefault();

        foreach (var item in LatestAccount)
        {
            Console.WriteLine("AccountID: " + item.AccountId + "  Date of Bill: " + item.DateOfBill + "  Group: "+ item.Group);
        }
        Console.ReadLine();
    }
}
class  Billing
{
    public int AccountID { get; set; }
    public string Group { get; set; }
    public DateTime DateOfBill { get; set; }
}

低于你想要的？ 如果你告诉我你想要的输出，我可以修改我的答案。