c# - Entity Framework Many-to-Many Inserting Fine, But Not Properly Updating -

good morning!

i have many-to-many relationship between employee , skill entities. when create new employee, skills select added database without problem. however, when update employee, employee content updates, none of skills added/removed. see being passed repository, not updating database.

i have following many-to-many relationship:

public class employee : baseentity {     public string firstname { get; set; }     public string lastname { get; set; }     public string jobtitle { get; set; }      public virtual icollection<skill> skills { get; set; } } 

and:

public class skill : baseentity {     public string name { get; set; }      public virtual icollection<employee> employees { get; set; } } 

my controller adds/removes employee's skills through following method:

public actionresult edit(int id, employeeeditviewmodel viewmodel) {     try     {         if (!modelstate.isvalid)         {             viewmodel.skillslist = _skillservice.getall().tolist();             return view(viewmodel);         }          var employee = mapper.map<employee>(viewmodel);          updateskills(employee, viewmodel.newskills);          _employeeservice.update(employee);          return redirecttoaction("index");     }     catch(exception e)     {         modelstate.addmodelerror("", e.message);         viewmodel.skillslist = _skillservice.getall().tolist();         return view(viewmodel);     } }        private void updateskills(employee employee, ienumerable<int> updatedskills)     {         if (employee.skills != null)         {             var updatedskillslist = updatedskills ilist<int> ?? updatedskills.tolist();             var addedskills = updatedskillslist.except(employee.skills.select(x => x.id));             var removedskills = employee.skills.select(x => x.id).except(updatedskillslist);              addedskills.foreach(x => employee.skills.add(_skillservice.getbyid(x)));             removedskills.foreach(x => employee.skills.remove(_skillservice.getbyid(x)));         }         else         {             employee.skills = new list<skill>();             newskills.foreach(x => employee.skills.add(_skillservice.getbyid(x)));         }     } 

the employee inserted/updated generic repository:

public void insert(tentity entity) {     if (entity == null)         throw new argumentnullexception("entity");      try     {         _dbset.add(entity);         _dbcontext.savechanges();     }     catch (dbentityvalidationexception ex)     {         throwvalidationerror(ex);     } }       public void update(tentity entity)     {         if (entity == null)             throw new argumentnullexception("entity");          try         {             _dbset.attach(entity);             _dbcontext.entry(entity).state = entitystate.modified;             _dbcontext.savechanges();         }         catch (dbentityvalidationexception ex)         {             throwvalidationerror(ex);         }     } 

here how employee object being called data context.

my constructor:

protected readonly ntierapplicationsdatacontext _dbcontext;         protected readonly dbset<tentity> _dbset;          public efrepository(ntierapplicationsdatacontext dbcontext)         {             _dbcontext = dbcontext;             _dbset = _dbcontext.set<tentity>();         }  

here find method object:

public tentity getbyid(int id)         {             return _dbset.find(id);         } 

i think must update employee self after editing skills below

private void updateskills(employee employee, ienumerable<int> updatedskills) {     if (employee.skills != null)     {         var updatedskillslist = updatedskills ilist<int> ?? updatedskills.tolist();         var addedskills = updatedskillslist.except(employee.skills.select(x => x.id));         var removedskills = employee.skills.select(x => x.id).except(updatedskillslist);          addedskills.foreach(x => employee.skills.add(_skillservice.getbyid(x)));         removedskills.foreach(x => employee.skills.remove(_skillservice.getbyid(x)));           // here           _employeeservice.update(employee);     }     else     {         employee.skills = new list<skill>();         newskills.foreach(x => employee.skills.add(_skillservice.getbyid(x)));     } } 

edit: check mapping

edit:

i think mapping entities has problem, can approach

public actionresult edit(int id, employeeeditviewmodel viewmodel) {    try    {     if (!modelstate.isvalid)     {         viewmodel.skillslist = _skillservice.getall().tolist();         return view(viewmodel);     }      //here mapper not attaching employee context     //var employee = mapper.map<employee>(viewmodel);      can      var employee = _employeeservice.getbyid(viewmodel.id);     // after ... update user did view model except id id won't change     employee = mapper.map<employee>(viewmodel, employee);     // think mapping have overload map destination. can set setup mappnig in startup ignore updating ids              updateskills(viewmodel.newskills);      _employeeservice.update(employee);      return redirecttoaction("index"); } catch(exception e) {     modelstate.addmodelerror("", e.message);     viewmodel.skillslist = _skillservice.getall().tolist();     return view(viewmodel); } 

}