编辑代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace HelloWorldApplication{

    class Student
{
    public int StudentID { get; set; }
    public String StudentName { get; set; }
    public int Age { get; set; }
}

   class HelloWorld{
      static void Main(string[] args){
             Student[] studentArray = { 
                    new Student() { StudentID = 1, StudentName = "John", age = 18 } ,
                    new Student() { StudentID = 2, StudentName = "Steve",  age = 21 } ,
                    new Student() { StudentID = 3, StudentName = "Bill",  age = 25 } ,
                    new Student() { StudentID = 4, StudentName = "Ram" , age = 20 } ,
                    new Student() { StudentID = 5, StudentName = "Ron" , age = 31 } ,
                    new Student() { StudentID = 6, StudentName = "Chris",  age = 17 } ,
                    new Student() { StudentID = 7, StudentName = "Rob",age = 19  } ,
           };
         // 使用LINQ查找青少年学生
         Student[] teenAgerStudents = studentArray.Where(s => s.age > 12 && s.age < 20).ToArray();       
        // 使用LINQ查找名字为Bill的第一位学生 
        Student bill = studentArray.Where(s => s.StudentName == "Bill").FirstOrDefault();        
        // 使用LINQ查找StudentID为5的学生        
        Student student5 = studentArray.Where(s => s.StudentID == 5).FirstOrDefault();
                 Console.Write(bill);
        }
   }
}