//order by first then last name using lambda
 static void OrderBy(Student[] students)
 {
     var sorted=students.OrderBy(student => student.firstName).ThenBy(student => student.lastName);
     foreach (var student in sorted)
     {
         Console.WriteLine(student.firstName + " " + student.lastName);
     }
 }
 // order be first then last name using LINQ
 static void OrderByLINQ(Student[] students)
 {
     var sorted = from student in students
                  orderby student.firstName, student.lastName
                  select student;
     foreach (var student in sorted)
     {
         Console.WriteLine(student.firstName + " " + student.lastName);
     }
 }
 //find students with age between 18 and 24
 public static void FindBetween18and24(Student[] students)
 {
     var arr = from student in students
               where student.age>18 && student.age<24
               select student;
     foreach (var student in arr)
     {
         Console.WriteLine(student.firstName + " " + student.lastName);
     }
 }
 //find students whose first name is before its last name alphabetically
 public static void Find(Student[] students)
 {
     var arr=from student in students
     where student.firstName.CompareTo(student.lastName) == -1
     select student;
     foreach (var student in arr)
     {
         Console.WriteLine(student.firstName + " "+ student.lastName);
     }
 }