c# linq goup by实例

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Collections;

namespace WebApplication22
{
public partial class Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
BindStudents();
}
}
/// <summary>
/// Binding the number of students in each school.
/// </summary>
private void BindStudents()
{
GridView1.DataSource = GetStudentCount();
GridView1.DataBind();
}
/// <summary>
/// Obtain the number of students in each school.
/// </summary>
/// <returns></returns>
private IList GetStudentCount()
{
List<Student> Students = GetStudents();
var query = from a in Students
group a by a.SchoolID into b
select new
{
SchoolID = b.Key,
TotalPenNumer=b.Sum(c=>c.PenNumber)
};
return query.ToList();
}
/// <summary>
/// Get the list of students.
/// </summary>
/// <returns></returns>
private List<Student> GetStudents()
{
List<Student> students = new List<Student>();
students.Add(new Student(1, "student1", 1, 1));
students.Add(new Student(2, "student2", 2, 1));
students.Add(new Student(3, "student3", 3, 2));
students.Add(new Student(4, "student4", 4, 3));
students.Add(new Student(5, "student5", 5, 3));
students.Add(new Student(6, "student6", 6, 3));
return students;
}
}
/// <summary>
/// Class of student.
/// </summary>
public class Student
{
public Student() { }
public Student(int _studentID, string _studentName,int _penNumber, int _schoolID)
{
this.StudentID = _studentID;
this.StudentName = _studentName;
this.PenNumber = _penNumber;
this.SchoolID = _schoolID;
}
public int StudentID { get; set; }
public string StudentName { get; set; }
public int PenNumber { get; set; }
public int SchoolID { get; set; }
}
}