using System;

using System.Linq;

​

​

class School

{

    public int Number {get;set;}

    public Student[] Students{get;set;}

}

​

class Student 

{

    public string Name {get;set;}

}

​

public class Program

{

    public static void Main()

    {

        var schools = new [] {

            new School{ Number = 1, Students = new [] { new Student{ Name="Bob"}, new Student{ Name="Jack"} }},

            new School{ Number = 2, Students = new [] { new Student{ Name="Jim"}, new Student{ Name="John"} }}

        };

        var allStudents = schools.SelectMany(s => s.Students);

        var allStudents2 = schools.SelectMany(s => s.Students, (sc, st) => new {sc.Number, st.Name});

        foreach(var student in allStudents){

            Console.WriteLine(student.Name);

        }

        foreach(var data in allStudents2){

            Console.WriteLine(data.Name + " " + data.Number);

        }       

    }

}