Linq-1查询语言

查询语言我们了解很多，大体上他们的思路语言都是相同的，linq也不难，只是我们把它想的太复杂了而已。Linq语言集成化查询
基础:1，泛型 2，lambda
from 元素 in 集合
where 元素条件
orderby 元素.属性 ascending
group 元素 by 元素.属性
select 元素

看段练习吧...

//查询出集合中年龄大于25的学生

//查询出集合中年龄大于25，且以“哈”字开头的学生

using System;
using System.Linq;
using System.Collections.Generic;
 public class studyLinq
 {
     public static void Main()
     {
         /*获取他们的扩展名*/
         string file = "sdfhue.gawei.ge..gaew.html";
         Console.WriteLine(file.GetFileType());
         string ttt= "dfhue,ge.dfe.mp3";
         Console.WriteLine(ttt.GetFileType());
        List<Student> list = new List<Student>();
        list.Add(new Student(){Age=10,Name="Jack"});
        list.Add(new Student(){Age=67,Name="Mack"});
        list.Add(new Student(){Age=23,Name="Dack"});
        list.Add(new Student(){Age=26,Name="哈密瓜"});
        list.Add(new Student(){Age=8,Name="Eack"});
        list.Add(new Student(){Age=34,Name="Hack"});
        list.Add(new Student(){Age=18,Name="小红"});
        //查询出集合中年龄大于25的学生
        IEnumerable<Student> result = list.Where<Student>(p=>p.Age>25);
        foreach(Student s in result)
        {
         Console.WriteLine(s.Age +" "+ s.Name);
        }
        //查询出集合中年龄大于25，且以“哈”字开头的学生
        IEnumerable<Student> result1 = list.Where(p => p.Age>25 &&p.Name.StartsWith("哈"));
         foreach(Student dd in result1)
         {
 
             Console.WriteLine(dd.Name + " " + dd.Age);
             }
         
     }
  
 public static void Test()
{
    int[] a  = {2,3,5,6,7,29,34,45,85,8,9,54,54,56,5};
    //var c = a.Where(p=>{return p>20});
    IEnumerable<int> c = a.Where(p=> p>20);
    foreach(int d in c)
    {
      Console.WriteLine(d);
    }
  }
 }
public class Student
{
    public string Name
    {
     get;
     set;
    }
    public int Age
    {
      get;
      set;
    }
}
 
public static class ExetendMethod
{
    public static string GetFileType(this string str)
    {
        string[] strs = str.Split('.');
        return strs[strs.Length-1];
    }
     
} 