InsertOnSubmit method throws NullReferenceException ... Linq to sql C# entity/DataContext class -

here's datacontext class:

public class dealer : datacontext {     public table<vehicle> vehicles;     public table<customer> customers => gettable<customer>();     public table<account> accounts;     public table<transaction> transactions;     public dealer(string connection) : base(connection) { } } 

here's customer class:

[table(name="customers")] public class customer {     [column(isprimarykey = true, dbtype = "int not null identity", isdbgenerated = true, canbenull = false)]     public int customerid { get; set; }      [column(canbenull = false)]     public string firstname { get; set; }      [column(canbenull = false)]     public string lastname { get; set; }      [column(canbenull = false)]     public string ssn { get; set; }      public override string tostring()     {         return string.concat(this.firstname, " ", this.lastname, " ", this.ssn);     }      private entityset<vehicle> vehicles = null;     [association(storage = "vehicles", otherkey = "customerid", thiskey = "customerid")]     public entityset<vehicle> vehicles { get; set; }      //implement inotifypropertychanged     public event propertychangedeventhandler propertychanged;      private void notifypropertychanged(string propertyname)     {         propertychanged?.invoke(this, new propertychangedeventargs(propertyname));     } } 

here's code throws nullreferenceexception:

private void button_click(object sender, routedeventargs e) {     customer c = new customer() { firstname="john", lastname="smith", ssn = "123456" };     dealer d = new dealer(app.connectionstring);     d.customers.insertonsubmit(c);    //d.customers null , throws null reference exception.!!!     try     {       d.submitchanges();     }     catch (exception x)     {       messagebox.show(x.message);     } 

i have googled many hours , can't figure out why it's throwing nullreferenceexception... (found lot of other posts non of solutions seem work me )

please ...

thanks in advance.

i had same problem yesterday. removing getters , setters datacontext class helped. way i'd change customerid column property addingautosync=autosync.oninsert