linq group by应用一

class Person
{
public Person() { }
public string ID { get; set; }
public string ID1 { get; set; }
public string Caption { get; set; }
public string ID2 { get; set; }
public int Value { get; set; }
public DateTime CollectTime { get; set; }
}

List<Person> persons = new List<Person>();
Person person1 = new Person();
person1.ID = "1";
person1.ID1 = "A";
person1.ID2 = "A1";
person1.Value = 22;
person1.CollectTime = new DateTime(2011, 11, 11);
persons.Add(person1);
Person person2 = new Person();
person2.ID = "2";
person2.ID1 = "B";
person2.ID2 = "B1";
person2.Value = 33;
person2.CollectTime = new DateTime(2011, 12, 11);
persons.Add(person2);
Person person3 = new Person();
person3.ID = "1";
person3.ID1 = "C";
person3.ID2 = "C1";
person3.Value = 22;
person3.CollectTime = new DateTime(2013, 11, 11);
persons.Add(person3);
Person person4= new Person();
person4.ID = "1";
person4.ID1 = "C";
person4.ID2 = "C1";
person4.Value = 22;
person4.CollectTime = new DateTime(2012, 11, 11);
persons.Add(person4);
var query = from c in persons
orderby c.CollectTime
group c by new { id = c.ID, id1 = c.ID1, id2 = c.ID2 } into r
select r;
foreach (var group in query)
{
//输出分组依据的字段
Console.WriteLine(group.Key);

Console.WriteLine(group.First());
// 输出组内成员
//foreach (var score in group)
//{
//    Console.WriteLine(score);
//}
}