c# - "An entity object cannot be referenced by multiple instances of IEntityChangeTracker" when adding a entity to context -

i coding mvc app contains couple of many-to-many associations. 1 of them custom role <---> account association. have table full of pre-defined roles user can choose. created viewmodel holds entity model , few collections use, 1 of them roles collection. populate create form these values , resolve them again on [httppost] create action.

here relevant code:

viewmodel class:

public class accountsviewmodel {     public accounts account { get; set; }      public list<roles> roleslist { get; set; } } 

controller code:

public actionresult create() {     accountsviewmodel viewmodel = new accountsviewmodel();     viewmodel.roleslist = rolesservice.getallroles();       return view(viewmodel);   }  [httppost] [validateantiforgerytoken] public actionresult create(accountsviewmodel viewmodel) {     if (modelstate.isvalid)     {         foreach(roles role in viewmodel.roleslist)         {              if (role.isselected)              {                   roles selectedrole = rolesservice.getrole(role.id);                   viewmodel.account.roles.add(selectedrole);              }          }                  //some more code here...                  accountsservice.addaccount(viewmodel.account);     } } 

custom service class (accountsservice)

public void addaccount(accounts newaccount) {     //appdatacontext instance of <model>container     appdatacontext.accountsset.add(newaccount);     appdatacontext.savechanges(); } 

and create view:

<div class="form-group">     @html.labelfor(model => model.account.roles, htmlattributes: new { @class = "control-label col-md-2" })     <div class="col-md-10">         @for (int = 0; < model.roleslist.count; i++)         {             @html.hiddenfor(m => m.roleslist[i].id)             @html.checkboxfor(m => m.roleslist[i].isselected)             @html.labelfor(m => m.roleslist[i].isselected, model.roleslist[i].name)             <br />         }     </div> </div> 

now actual problem, each time try add new accounts object, error "an entity object cannot referenced multiple instances of ientitychangetracker." have looked @ few posts found on internet, can't associate them possible errors made in code. can me out here?

the problem roles of newaccount still attached context of roleservice. entity can attached 1 context @ time.

you can either call context.entity(...).detach() detach entity, or better role change tracking disabled , without proxy creation, give huge speed boost to:

context.configuration.autodetectchangesenabled = false; context.configuration.proxycreationenabled = false; 

even better create new context within using block inside of rolesservice.getrole(...) way context won't polluted (and slow) on time.