.net - Issue with related entity collection in Entity Framework 5 -

i have below 4 entity in project.

student

public int studentid { get; set; } public string studentname { get; set; } public int standardid { get; set; }  public virtual standard standard { get; set; } public virtual studentaddress studentaddress { get; set; } public virtual icollection<course> courses { get; set; } 

teacher

public int teacherid { get; set; } public string teachername { get; set; } public nullable<int> standardid { get; set; }  public virtual icollection<course> courses { get; set; } public virtual standard standard { get; set; } 

standard

public int standardid { get; set; } public string standardname { get; set; } public string description { get; set; }  public virtual icollection<student> students { get; set; } public virtual icollection<teacher> teachers { get; set; } 

course

public int courseid { get; set; } public string coursename { get; set; } public string location { get; set; } public int teacherid { get; set; }  public virtual teacher teacher { get; set; } public virtual icollection<student> students { get; set; } 

if try directly access list of courses student entity, getting count of courses zero.

   using (schooldbentities db = new schooldbentities())     {         var query = (from s in db.students                      select s).firstordefault<student>();          foreach (var item in query.courses)         {                 console.writeline(item.coursename);                             }         console.readline();     } 

but if access courses list below, getting data properly, issue in first approach? missing anything? hope below 1 not efficient way access data.

    using (schooldbentities db = new schooldbentities())     {         var query =   (from s in db.students                                                         select s).firstordefault<student>();          foreach (var item in query.standard.teachers)         {             foreach (var crs in item.courses)             {                 console.writeline(crs.coursename);             }         }                         console.readline();     }