Question

我已经阅读了下面的代码，但是不明白group子句如何进行分组

请帮忙。我是c＃的新手。

public static List<Student> GetStudents()
        {
            // Use a collection initializer to create the data source. Note that each element 
            //  in the list contains an inner sequence of scores.
            List<Student> students = new List<Student>
        {
           new Student {First="Svetlana", Last="Omelchenko", ID=111, Scores= new List<int> {97, 72, 81, 60}},
           new Student {First="Claire", Last="O'Donnell", ID=112, Scores= new List<int> {75, 84, 91, 39}},
           new Student {First="Sven", Last="Mortensen", ID=113, Scores= new List<int> {99, 89, 91, 95}},
           new Student {First="Cesar", Last="Garcia", ID=114, Scores= new List<int> {72, 81, 65, 84}},
           new Student {First="Debra", Last="Garcia", ID=115, Scores= new List<int> {97, 89, 85, 82}} 
        };

            return students;

        }
List<Student> students = GetStudents();

            // Write the query. 
            var studentQuery =
                from student in students
                let avg = (int)student.Scores.Average()
                group student by (avg == 0 ? 0 : avg / 10);

我不明白StudentQuery是如何生成的。提前谢谢。

Answer 1

分组是指将数据放入组中的操作，以便每个组中的元素共享一个公共属性。GroupBy将学生分成小组 - 平均为0-9,10-19,20-29的小组，30-39等你应该看一下 http://msdn.microsoft.com/en-us//library/bb546139.aspx

P.S。在

 group student by (avg == 0 ? 0 : avg / 10);

对我来说似乎太过分了。您可以将其更改为更简单

 group student by (avg / 10);

pps：我更喜欢LINQ的其他风格，但它完全是个人选择。另一种风格是

var studentQuery = students.GroupBy(x => x.Scores.Average() / 10);

LINQ中的group by子句

1 个答案: