Question

我正在学习这本书：

使用C＃4.0 LINQ到对象

好的，我的问题：

我有两个课程：联系和 CallLog 。它看起来像：

public class Contact
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public string Email { get; set; }
        public string Phone { get; set; }
        public DateTime DateOfBirth { get; set; }
        public string State { get; set; }
};

public class CallLog
    {
        public string Number { get; set; }
        public int Duration { get; set; }
        public bool Incoming { get; set; }
        public DateTime When { get; set; }
    }

关系： Contact.Phone等于CallLog.Number

两个类有方法：SampleData（）。该metod返回一个简单的List＆lt;＆gt;与联系人和CallLogs。

List<Contact> contacts = Contact.SampleData();
List<CallLog> callLogs = CallLog.SampleData();

我现在有查询，它返回一个结果排序，按照联系人的电话号码排序（完全是联系人，谁调用的是0）。

var query = (from callLog in callLogs
                        group callLog by callLog.Number into g
                        select new
                        {
                            contact = contacts.Where(c=>c.Phone == g.Key),
                            how_much = g.Count(),
                        });

foreach(var q in query){
     foreach(var qq in q.contact){
          Console.WriteLine(qq.FirstName + " calls " + q.how_much + " times");
     }
}

它返回例如：

Stephan调用5次

苏菲打电话2次

汤姆打电话5次

等...

现在我想按通话时间进行分组（5次，2次......），以及我通过查询写下一个查询：

var query2 = from q in query
                         group q by q.how_much into g
                         select new
                         {
                             what_number       = g.Key, // f.e 5 times
                             count_what_number = g.Count(), // 5 times have 2 person
                             who               = g // collection for person
                         };
foreach (var q in query2)
            {
                Console.WriteLine(q.what_number + " calls have done: ( " + q.count_what_number + ") peoples"));
                foreach (var qq in q.who)
                {
                    foreach (var qqq in qq.contact)
                    {
                        Console.WriteLine("   " + qqq.FirstName);
                    }
                }
            }

结果：

5 calls have done: (2 peoples):
     Stephan
     Tom
2 calls have done: (1 peoples):       
     Sophie

通过1个查询进行此查询的任何方式（按组分组不在两个查询中）？

Answer 1

这是另一种方法：

List<Contact> contacts = Contact.SampleData();
List<CallLog> callLogs = CallLog.SampleData();

var q = from callLog in callLogs
        group callLog by callLog.Number into g
        join c in contacts on g.Key equals c.Phone
        let row = new { g = g, c = c }
        group row by row.g.Count() into g2
        select new
        {
            People = g2.Select((x) => x.c.FirstName).ToArray(),
            Count = g2.Key
        };

foreach (var qq in q)
{
    Console.WriteLine(qq.Count + ": " + string.Join(", ", qq.People));
}

打印类似：

4: Tom, John
2: Adam

Answer 2

解决：

 var query = (from callLog in callLogs
                         group callLog by callLog.Number into g
                         select new
                         {
                             who = contacts.Where(c => c.Phone == g.Key),
                             how_much = g.Count()
                         }).GroupBy(c=>c.how_much);

     foreach (var q in query)
                {
                    Console.WriteLine(q.Key + " " + q.Count());
                    foreach (var qq in q)
                    {
                        foreach (var qqq in qq.who)
                        {
                            Console.WriteLine(qqq.FirstName + " " + qqq.LastName);
                        }
                    }
                }

来自查询的LINQ query2

2 个答案: