Student student1WithUser1 = null; 
Student student1WithUser2 = null;

//User 1 gets student
using (var context = new SchoolDBEntities())
{
    context.Configuration.ProxyCreationEnabled = false;
    student1WithUser1 = context.Students.Where(s => s.StudentID == 1).Single();
}
//User 2 also get the same student
using (var context = new SchoolDBEntities())
{
    context.Configuration.ProxyCreationEnabled = false;
    student1WithUser2 = context.Students.Where(s => s.StudentID == 1).Single();
}
//User 1 updates Student name
student1WithUser1.StudentName = "Edited from user1";

//User 2 updates Student name
student1WithUser2.StudentName = "Edited from user2";

//User 1 saves changes first
using (var context = new SchoolDBEntities())
{
    try
    {
        context.Entry(student1WithUser1).State = EntityState.Modified;
        context.SaveChanges();
    }
    catch (DbUpdateConcurrencyException ex)
    {
        Console.WriteLine("Optimistic Concurrency exception occured");
    }
}

//User 2 saves changes after User 1. 
//User 2 will get concurrency exection 
//because CreateOrModifiedDate is different in the database 
using (var context = new SchoolDBEntities())
{
    try
    {
        context.Entry(student1WithUser2).State = EntityState.Modified;
        context.SaveChanges();
    }
    catch (DbUpdateConcurrencyException ex)
    {
        Console.WriteLine("Optimistic Concurrency exception occured");
    }
}