Linq——Count、Sum、Min、Max、Average

/* from: http://blog.sina.com.cn/s/blog_412ec72c0100mall.html */

using System;  
using System.Data;  
using System.Configuration;  
using System.Linq;  
using System.Web;  
using System.Web.Security;  
using System.Web.UI;  
using System.Text;  
using System.Web.UI.WebControls;  
using System.Web.UI.WebControls.WebParts;  
using System.Web.UI.HtmlControls;  
using System.Collections.Generic;  
using System.Collections;  
  
public partial class _Default : System.Web.UI.Page  
{  
    protected void Page_Load(object sender, EventArgs e)  
    {  
        #region 用Count()得出查询结果的个数   
        Response.Write("<hr>用Count()得出查询结果的个数<br>");  
        var langCount = (from s in GetStudents()  
                           select s.Language)  
                           .Distinct()  
                           .Count();  
        Response.Write(string.Format("<div class='result'>{0}</div>", langCount));  
        #endregion  
 
        #region 用Count()的Lambda表达式满足条件的元素个数   
        Response.Write("<hr>用Count()得出查询结果的个数<br>");  
        var ageCoun = (from s in GetStudents()  
                          select s.Age)  
                          .Count(a=>a>22);  
        Response.Write(string.Format("<div class='result'>{0}</div>", ageCoun));  
        #endregion  
 
        #region 用Sum()将查询结果相加   
        Response.Write("<hr>用Sum()将查询结果相加<br>");  
        var ageSum = (from s in GetStudents()  
                      select s.Age)  
                       .Sum();  
        //var ageSum = GetStudents().Sum(s=>s.Age);   
        Response.Write(string.Format("<div class='result'>{0}</div>", ageSum));  
        #endregion  
 
        #region 用Min()得出查询结果的最小值   
        Response.Write("<hr>用Min()得出查询结果的最小值<br>");  
        var ageMin = (from s in GetStudents()  
                      select s.Age)  
                       .Min();  
        //var ageMin = GetStudents().Min(s => s.Age);   
        Response.Write(string.Format("<div class='result'>{0}</div>", ageMin));  
        #endregion  
 
        #region 用Max()得出查询结果的最大值   
        Response.Write("<hr>用Max()得出查询结果的最大值<br>");  
        var ageMax = (from s in GetStudents()  
                      select s.Age)  
                       .Max();  
        //var ageMax = GetStudents().Max(s => s.Age);   
        Response.Write(string.Format("<div class='result'>{0}</div>", ageMax));  
        #endregion  
 
        #region 用Average()得出查询结果的平均值   
        Response.Write("<hr>用Average()得出查询结果的平均值<br>");  
        var ageAverage = (from s in GetStudents()  
                      select s.Age)  
                      .Average();  
        //var ageAverage = GetStudents().Average(s => s.Age);   
        Response.Write(string.Format("<div class='result'>{0}</div>", ageAverage));  
        #endregion   
    }  
 
    #region 构造一个学生集合体   
    private List<Student> GetStudents()  
    {  
        List<Student> students = new List<Student> {  
             new Student{ Name="YOUNG", Age=25, Language="Chinese"},  
             new Student{ Name="JESSIE", Age=21, Language="Scotland"},  
             new Student{ Name="KELLY", Age=18, Language="English"},  
             new Student{ Name="JUNE", Age=20, Language="English"},  
             new Student{ Name="ADRIAN", Age=22, Language="Italy"},  
             new Student{ Name="BRUCE", Age=17, Language="Scotland"},  
             new Student{ Name="BRANT", Age=30, Language="Germany"},  
             new Student{ Name="BEN", Age=25, Language="Chinese"}  
        };  
        return students;  
    }  
    #endregion   
}  
 
#region 学生类   
class Student  
{  
    public int Age { get; set; }  
    public string Name { get; set; }  
    public string Language { get; set; }  
}  
#endregion