c# - How can i get the correct information to display in my listbox? -

i have 2 listboxes can move exercises available list of exercises list of selected exercises specific user. current problem selected list (aka regimeitems) shows exercises of users.

i believe problem lies in chosenexercises(at bottom of controller) getting null reference exception at:

var regimeids = model.savedrequested.split(',').select(x => int.parse(x));

controller.cs

    [httpget]             public actionresult exerciseindex(int? id, userexerciseviewmodel vmodel)             {                 user user = db.users.find(id);                 user.regimeitems = chosenexercises();                 userexerciseviewmodel model = new userexerciseviewmodel { availableexercises = getallexercises(), requestedexercises = chosenexercises(user, vmodel) };                 user.regimeitems = model.requestedexercises;                 return view(model);             }              [httppost]             public actionresult exerciseindex(userexerciseviewmodel model, string add, string remove, string send, int id)             {                 user user = db.users.find(id);                 user.regimeitems = model.requestedexercises;;                 restoresavedstate(model);                 if (!string.isnullorempty(add))                     addexercises(model, id);                 else if (!string.isnullorempty(remove))                     removeexercises(model, id);                         savestate(model);                 return view(model);             }              void savestate(userexerciseviewmodel model)             {                 model.savedrequested = string.join(",", model.requestedexercises.select(p => p.regimeitemid.tostring()).toarray());                 model.availableexercises = getallexercises().tolist();             }              void restoresavedstate(userexerciseviewmodel model)             {                 model.requestedexercises = new list<regimeitem>();                  //get stored items                 if (!string.isnullorempty(model.savedrequested))                 {                     string[] exids = model.savedrequested.split(',');                     var exercises = getallexercises().where(p => exids.contains(p.exerciseid.tostring()));                     model.availableexercises.addrange(exercises);                 }             }              private list<exercise> getallexercises()             {                 return db.exercises.tolist();             }              private list<regimeitem> chosenexercises(user user, userexerciseviewmodel model)//regimeitem regimeitem)             { var regimeids = model.savedrequested.split(',').select(x => int.parse(x));             return db.regimeitems.where(e => regimeids.contains(e.regimeitemid)).tolist();             //return db.users.where(r => r.regimeitems = user.userid);             //return db.users.where(r => r.regimeitems.regimeitemid == user.userid);             } 

models

  public class user     {         public int userid { get; set; }         public icollection<regimeitem> regimeitems { get; set; }         public user()         {             this.regimeitems = new list<regimeitem>();         }      }     public class regimeitem     {         public int regimeitemid { get; set; }         public exercise regimeexercise { get; set; }     } 

viewmodel

public class userexerciseviewmodel {     public list<exercise> availableexercises { get; set; }     public list<regimeitem> requestedexercises { get; set; }     public int? selectedexercise { get; set; }     public int[] availableselected { get; set; }     public int[] requestedselected { get; set; }     public string savedrequested { get; set; } } 

try changing

return db.users.where(r => r.regimeitems = user.userid); 

to

return db.users.where(r => r.regimeitems.regimeitemid == user.userid); 

because way read you're trying match int object.

edit: error resulted op found himself.

"it seems regimeitems collection of regimeitem - not have have single id. needed .where(u => u.userid == user.userid) , select regimeitems associated user .selectmany(u => u.regimeitems).tolist(); help, if update answer mark yours correct answer." -nilmag