I'm trying to sort out this issue but as I'm learning a lot of this stuff as I go along I'd really appreciate it if someone could explain where I'm going wrong and/or some good resources where I can read up.
So, I have a model based on my Entity Framework model of my database and a viewmodel representing properties in that model. I've built a Kendo grid to display the data (defined in a js file) and the method in the contoller returns a Json result set. Trouble is, when I try to display a value in a joined db table, if there hasn't been a key value set, I get a nullreferenceexception error. Obviously I'm missing part of the puzzle here as there must be a way of coding this to stop it happening. Any help would be gratefully received!
My model is like this:
namespace TrainingKendoUI.Models
{
using System;
using System.Collections.Generic;
public partial class TRAINING_EMPLOYEE_COURSES
{
public int EMP_COURSE_ID { get; set; }
public int EMPLOYEE_ID { get; set; }
public int COURSE_ID { get; set; }
public Nullable<System.DateTime> DATE_ATTENDED { get; set; }
public Nullable<decimal> COURSE_COST { get; set; }
public string COURSE_RESITS { get; set; }
public Nullable<int> PROVIDER_ID { get; set; }
public Nullable<int> EMP_COURSE_STATUS_ID { get; set; }
public Nullable<int> VENUE_ID { get; set; }
public virtual TRAINING_COURSES TRAINING_COURSES { get; set; }
public virtual TRAINING_EMPLOYEE_COURSE_STATUS TRAINING_EMPLOYEE_COURSE_STATUS { get; set; }
public virtual TRAINING_EMPLOYEES TRAINING_EMPLOYEES { get; set; }
public virtual TRAINING_PROVIDERS TRAINING_PROVIDERS { get; set; }
public virtual TRAINING_VENUES TRAINING_VENUES { get; set; }
}
}
My controller method looks like this:
public JsonResult EmployeeCourses_Read()
{
var model = db.TRAINING_EMPLOYEE_COURSES;
var ViewModel = new List<EmployeeCoursesIntersectionViewModel>();
foreach (var employee in model)
{
ViewModel.Add(new EmployeeCoursesIntersectionViewModel(employee));
}
return Json(ViewModel, JsonRequestBehavior.AllowGet);
}
and my view model lilke this:
namespace TrainingKendoUI.ViewModels
{
public class EmployeeCoursesIntersectionViewModel
{
#region Constructors
public EmployeeCoursesIntersectionViewModel()
{
}
public EmployeeCoursesIntersectionViewModel(TRAINING_EMPLOYEE_COURSES model)
{
this.empCourseId = model.EMP_COURSE_ID;
this.employee = model.TRAINING_EMPLOYEES.FIRST_NAME;
this.course = model.TRAINING_COURSES.COURSE_NAME;
this.dateAttended = model.DATE_ATTENDED;
this.cost = model.COURSE_COST;
this.resits = model.COURSE_RESITS;
//These lines will produce a NullReference error if not set through the front end...
this.provider = model.TRAINING_PROVIDERS.PROVIDER_NAME;
this.status = model.TRAINING_EMPLOYEE_COURSE_STATUS.EMP_COURSE_STATUS;
this.venue = model.TRAINING_VENUES.VENUE_NAME;
}
#endregion
#region Properties
public int empCourseId { get; set; }
public string employee { get; set; }
public string course { get; set; }
public Nullable<System.DateTime> dateAttended { get; set; }
public Nullable<decimal> cost { get; set; }
public string resits { get; set; }
public string provider { get; set; }
public string status { get; set; }
public string venue { get; set; }
#endregion
}
}
Do a null check on the object before setting it, i.e.
this.provider = model.TRAINING_PROVIDERS == null ? ""
: model.TRAINING_PROVIDERS.PROVIDER_NAME;
and you'll have to do similar for status and venue
this.status = model.TRAINING_EMPLOYEE_COURSE_STATUS== null ? ""
model.TRAINING_EMPLOYEE_COURSE_STATUS.EMP_COURSE_STATUS;
this.venue = model.TRAINING_VENUES== null ? ""
model.TRAINING_VENUES.VENUE_NAME;
Related
Code without AutoMapper:
List<CountryDM> countryDMList = _countryRepo.GetCountry();
List<CountryVM> countryVMList = new List<CountryVM>();
foreach (CountryDM countryDM in countryDMList)
{
countryVMList.Add(CountryVM.ToViewModel(countryDM));
}
return countryVMList;
I used AutoMapper for the above task. But it returns a NULL list. Please refer the below code:
List<CountryDM> countryDMList = _countryRepo.GetCountry();
Mapper.CreateMap<List<CountryDM>, List<CountryVM>>();
List<CountryVM> countryVMList = new List<CountryVM>();
return Mapper.Map<List<CountryVM>>(countryDMList);
public class CountryDM
{
public int ID { get; set; }
public string CountryCode { get; set; }
public string Description { get; set; }
}
public class CountryVM
{
public int ID { get; set; }
public string CountryCode { get; set; }
public string Description { get; set; }
}
You don't need to define a mapping between lists, just between objects, AutoMapper will know how to extrapolate that:
Mapper.CreateMap<CountryDM, CountryVM>();
the rest stays the same
This a simple project where users can search for job postings by area of expertise. The relationship between Areas and Postings are Many-to-many. I seem to be able to get to the very last part of retrieving the correctly filtered list, but getting back into the view model keeps giving me different errors:
ViewModel:
public class AreaOfertasViewModel
{
public Oferta UnaOferta { get; set; }
public SelectList AreasTrabajo { get; set; }
public IEnumerable<Oferta> Ofertas { get; set; }
public int idArea { get; set; }
public AreaOfertasViewModel()
{
this.UnaOferta = UnaOferta;
this.Ofertas = new List<Oferta>();
cargarAreas();
}
private void cargarAreas()
{
PostulaOfertaContext db = new PostulaOfertaContext();
this.AreasTrabajo = new SelectList(db.Areas, "areaId", "Area");
}
}
}
Controller:
public ActionResult SearchXArea()
{
return View(new AreaOfertasViewModel());
}
[HttpPost]
public ActionResult SearchXArea(AreaOfertasViewModel aovm)
{
int id = aovm.idArea;
PostulaOfertaContext db = new PostulaOfertaContext();
var area = db.Areas.Where(c => c.areaId == id);
var ofertas = from c in db.Ofertas.Where(r => r.AreaTrabajo == area)
select c;
aovm.Ofertas = (IEnumerable<Oferta>)ofertas.ToList();
return View(aovm);
}
The line giving me issues is
aovm.Ofertas = (IEnumerable)ofertas.ToList();
I've tried List<> for Ofertas, and I've tried leaving it as .ToList() without casting, and casting it as different things, but it gives me errors about not being able to cast it, and "Cannot compare elements of type 'System.Collections.Generic.List`1'. Only primitive types, enumeration types and entity types are supported."
What's the solution here?
Model for AreaTrabajo:
public class AreaTrabajo
{
[Key]
public int areaId { get; set; }
public string Area { get; set; }
public virtual List<Oferta> oferta { get; set; }
}
Model for Oferta:
public class Oferta
{
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
[Required]
public string Titulo { get; set; }
[Required]
public DateTime Vencimiento { get; set; }
[Required]
public string Cargo { get; set; }
[Required]
public int HorarioComienzo { get; set; }
[Required]
public int HorarioFin { get; set; }
[Required]
public string DescripcionTareas { get; set; }
public int Remuneracion { get; set; }
[Required]
public int RangoEdadMin { get; set; }
[Required]
public int RangoEdadMax { get; set; }
public string TipoFormacion { get; set; }
public string Idiomas { get; set; }
public string Competencias { get; set; }
public string OtrosEstudios { get; set; }
public string Estado { get; set; }
public virtual List<AreaTrabajo> AreaTrabajo { get; set; }
public virtual TipoContrato TipoContrato { get; set; }
public virtual Empresa Empresa { get; set; }
public virtual List<Postulante> Postulantes { get; set; }
}
Answer
[HttpPost]
public ActionResult SearchXArea(AreaOfertasViewModel aovm)
{
int id = aovm.idArea;
PostulaOfertaContext db = new PostulaOfertaContext();
var area = db.Areas.Where(c => c.areaId == id).FirstOrDefault();
var ofertas = db.Ofertas.Where(s => s.AreaTrabajo.All(e => e.areaId == area.areaId)).ToList();
aovm.Ofertas = ofertas;
return View(aovm);
}
Sorry if my question wasn't clear enough. I needed to filter out from the many-to-many relationship, and this solved it.
You are getting an error because the actual sql is executed when you call tolist(). The error is in your sql because you are comparing AreaTrabago to a list.
[HttpPost]
public ActionResult SearchXArea(AreaOfertasViewModel aovm)
{
int id = aovm.idArea;
PostulaOfertaContext db = new PostulaOfertaContext();
var area = db.Areas.Where(c => c.areaId == id).FirstOrDefault();
var ofertas = db.Ofertas.Where(s => s.AreaTrabajo.All(e => e.areaId == area.areaId)).ToList();
aovm.Ofertas = ofertas;
return View(aovm);
}
Sorry if my question wasn't clear enough. I couldn't get the many-to-many relationship, and this solved the filtering problem perfectly.
I have two tables in my database that have similar data but not same.
I'd like to show these tables in the same view. Looking in internet the most suggested practice is to use a ViewModel class.
So... These are my class tables:
iCareIndoorAlert.cs
[Table("iCareIndoorAlerts")]
public class iCareIndoorAlert
{
[Key]
[DisplayName("ID Allarme iCare indoor")]
public long AlertID { get; set; }
[DisplayName("ID Messaggio")]
public long MessageID { get; set; }
public string UUID { get; set; }
public int MAG { get; set; }
public int MIN { get; set; }
[DisplayName("Distanza")]
public float Dist { get; set; }
[DisplayName("Data ora")]
public DateTime DateTime { get; set; }
public virtual HttpPop3 HttpPop3 { get; set; }
}
iCareOutdoorAlert.cs
[Table("iCareOutdoorAlerts")]
public class iCareOutdoorAlert
{
[Key]
[DisplayName("ID Allarme iCare outdoor")]
public long AlertID { get; set; }
[DisplayName("ID Messaggio")]
public long MessageID { get; set; }
[DisplayName("Latitudine")]
public float Lat { get; set; }
[DisplayName("Longitudine")]
public float Lon { get; set; }
[DisplayName("Accuracy")]
public float Acc { get; set; }
[DisplayName("Data ora")]
public DateTime DateTime { get; set; }
}
After I created a ViewModel folder with a iCareAlertViewModel.cs class:
public List<iCareIndoorAlert> iCareIndoorAlert { get; set; }
public List<iCareOutdoorAlert> iCareOutdoorAlert { get; set; }
And added there rows in the iCareEntities.cs:
public DbSet<iCareIndoorAlert> iCareIndoorAlerts { get; set; }
public DbSet<iCareOutdoorAlert> iCareOutdoorAlerts { get; set; }
public DbSet<iCareAlertViewModel> iCareAlertsViewModels { get; set; }
After I generated the iCareAlertController.cs and run the view Index.cshtml but I get the error "Key not found". So in the ViewModel I added a dummy variable with [Key] attribute and now a get an error that says that can't find the iCareAlertViewModel table...
What am I doing wrong?
Thank you
First, don't create a DbSet for your view model, that's not necessary. A view model is a POCO that sits between your data models (i.e. your entities) and your user interface.
What you probably need to do is define an interface that has the properties that are common to your two entities, so something like this:
public interface IAlert
{
long AlertID { get; set; }
long MessageID { get; set; }
//etc...
}
Now each entity can implement that interface:
public class iCareIndoorAlert : IAlert
{
//snip
}
Now your viewmodel:
public class AlertViewModel : IAlert
{
public long AlertID { get; set; }
public long MessageID { get; set; }
//snip
}
So your view will now be something like this:
#model IEnumerable<My.Assembly.AlertViewModel>
#foreach(var alert in Model)
{
#Html.DisplayFor(m => m.AlertID)
//etc
}
Finally you need something to map your entities to your view model, you can use a library like Automapper but manually, it's something like this (including the action method and return):
public ActionResult Index()
{
List<IAlert> alerts = GetOutdoorAlerts(); //for example
List<AlertViewModel> alertViewModels = alert
.Select(a => new AlertViewModel
{
AlertID = a.AlertID,
MessageID = a.MessageID,
//etc...
});
return View(alertViewModels);
}
I have a Model like this
public class Challenge
{
public int ID { get; set; }
public string Name { get; set; }
public string Blurb { get; set; }
public int Points { get; set; }
public string Category { get; set; }
public string Flag { get; set; }
public List<string> SolvedBy { get; set; }
}
public class ChallengeDBContext : DbContext
{
public DbSet<Challenge> Challenges { get; set; }
}
and then Controller like this. But I cannot update the List "SolvedBy", the next time I step through with the debugger, the list is still empty.
[HttpPost]
public string Index(string flag = "", int id=0)
{
Challenge challenge = db.Challenges.Find(id);
if (flag == challenge.Flag)
{
var chall = db.Challenges.Find(id);
if (chall.SolvedBy == null)
{
chall.SolvedBy = new List<string>();
}
chall.SolvedBy.Add(User.Identity.Name);
db.Entry(chall).State = EntityState.Modified;
db.SaveChanges();
//congrats, you solved the puzzle
return "got it";
}
else
{
return "fail";
}
}
is there any way around it to make a list of strings kept in the database?
EF don't know how to store an array in database table so it just ignore it. You can create another table/entity or use XML/JSON to store the list. You can serialize the list before saving and deserialize it after loading from database
A List<T> in a model would normally map to a second table, but in your DbContext you only have a single table. Try adding a second table.
public class ChallengeDBContext : DbContext
{
public DbSet<Challenge> Challenges { get; set; }
public DbSet<Solution> Solutions {get; set;}
}
public class Challenge
{
public int ID { get; set; }
public string Name { get; set; }
public string Blurb { get; set; }
public int Points { get; set; }
public string Category { get; set; }
public string Flag { get; set; }
public List<Solution> SolvedBy { get; set; }
}
public class Solution
{
public int ID { get; set; }
public string Name { get; set; }
}
Then your controller can use code along the lines of...
var chall = db.Challenges.Find(id);
if (chall.SolvedBy == null)
{
chall.SolvedBy = new List<Solution>();
}
chall.SolvedBy.Add(new Solution {Name=User.Identity.Name});
None of the above has been tested and I may have made some mistakes there, but the general principle I want to illustrate is the fact that you need another table. The List<T> represents a JOIN in SQL.
I have two models, a code model and a tag model which are linked by a many to many relationship. I am trying to add a code entry that includes a possible selection of many tags using a view model (using check boxes for the tags in my view). I am getting the error:
The model item passed into the dictionary is of type 'System.Collections.Generic.List'1[StoRed.Models.Code]', but this dictionary requires a model item of type 'System.Collections.Generic.IEnumerable`1[StoRed.Models.CodeTagViewModel]'.
It feels like I need to somehow convert my data to the acceptable format before trying to save it into the table but I'm new to MVC and I am having trouble finding any useful information on the internet about my specific problem. Any help would be greatly appreciated.
The code model
public class Code
{
[Key]
public int CodeID { get; set; }
[Required]
[StringLength(30)]
public string Title { get; set; }
[Required]
[StringLength(150)]
public string Description { get; set; }
public DateTime DateAdded { get; set; }
public DateTime LastUpdated { get; set; }
[Required]
[StringLength(30)]
public string Project { get; set; }
[Required]
[StringLength(30)]
public string CMS { get; set; }
public int DotNetVersion { get; set; }
[Required]
[StringLength(150)]
public string Dependencies { get; set; }
[StringLength(30)]
public string Author { get; set; }
public string CodeFile { get; set; }
[Required]
[StringLength(100)]
public string TFSLocation { get; set; }
////Creates a relationship in the DB with Tag
//[ForeignKey("TagID")]
public virtual ICollection<Tag> Tags { get; set; }
////Purely for API
//[Required]
public int TagID { get; set; }
}
The Tag model
public class Tag
{
[Key]
public int TagID { get; set; }
[Required]
[StringLength(30)]
public string TagName { get; set; }
public virtual ICollection<Code> Code { get; set; }
}
The context
public class Context : DbContext
{
public DbSet<Code> Code { get; set; }
public DbSet<Tag> Tags { get; set; }
}
The view model
public class CodeTagViewModel
{
public Tag Tag { get; set; }
public Tag TagID { get; set; }
public List<Tag> Tags { get; set; }
public int CodeID { get; set; }
public string Title { get; set; }
public string Description { get; set; }
public DateTime DateAdded { get; set; }
public DateTime LastUpdated { get; set; }
public string Project { get; set; }
public string CMS { get; set; }
public int DotNetVersion { get; set; }
public string Dependencies { get; set; }
public string Author { get; set; }
public string CodeFile { get; set; }
public string TFSLocation { get; set; }
}
Relevant part of the code controller
[HttpPost]
public ActionResult Create(CodeTagViewModel codeTagViewModel)
{
if (ModelState.IsValid)
{
Code code = new Code();
Tag tag = new Tag();
var codeTag = new CodeTagViewModel();
code.Title = codeTagViewModel.Title;
code.Description = codeTagViewModel.Description;
code.DateAdded = codeTagViewModel.DateAdded;
code.LastUpdated = codeTagViewModel.LastUpdated;
code.Project = codeTagViewModel.Project;
code.CMS = codeTagViewModel.CMS;
code.DotNetVersion = codeTagViewModel.DotNetVersion;
code.Dependencies = codeTagViewModel.Dependencies;
code.Author = codeTagViewModel.Author;
code.CodeFile = codeTagViewModel.CodeFile;
code.TFSLocation = codeTagViewModel.TFSLocation;
code.Tags = codeTagViewModel.Tags;
db.Code.Add(code);
db.SaveChanges();
return RedirectToAction("Index");
}
return View(codeTagViewModel);
}
Your best bet is to create some kind of provider/manager/service/factory/handler - choose a name that makes most sense in terms of the job it is doing within the flow of data through your system - that is responsible for taking the ViewModel and mapping the properties of the ViewModel into an instance of the domain model before persisting the domain model to the data store, either itself or by passing the hydrated domain model to a repository layer. You can either do this manually or by using something like AutoMapper. Here's a quick manual example:
Create a CommandHandlers folder in your web project with the interface and dependant handler:
public interface ICodeCommandHandler
{
int Save(CodeTagViewModel input);
}
public class CodeCommandHandler : ICodeCommandHandler
{
private IRepository<Code> repository;
public CodeCommandHandler(IRepository<Code> repository)
{
this.repository = repository;
}
public int Save(CodeTagViewModel input)
{
Code code = new Code();
Tag tag = new Tag();
code.Title = input.Title;
code.Description = input.Description;
code.DateAdded = input.DateAdded;
code.LastUpdated = input.LastUpdated;
code.Project = input.Project;
code.CMS = input.CMS;
code.DotNetVersion = input.DotNetVersion;
code.Dependencies = input.Dependencies;
code.Author = input.Author;
code.CodeFile = input.CodeFile;
code.TFSLocation = input.TFSLocation;
code.Tags.Add(tag);
return repository.Save(code);
}
}
Then in your controller, inject the ICodeCommandHandler in via constructor injection, the same as you do with the repository in the CodeCommandHandler:
private readonly ICodeCommandHandler commandHandler;
public CodeController(ICodeCommandHandler commandHandler)
{
this.commandHandler = commandHandler;
}
[HttpPost]
public ActionResult Create(CodeTagViewModel codeTagViewModel)
{
if (!ModelState.IsValid)
{
return View(codeTagViewModel);
}
var id = codeCommandHandler.Save(codeTagViewModel);
// maybe do something useful with the document id after save
return RedirectToAction("Index");
}
To keep the Repository nice and simple, here's how that could look:
public interface IRepository<T>
{
int Save(T entity);
}
public class CodeRepository : IRepository<Code>
{
public int Save(Code entity)
{
using (var context = new Context())
{
context.Code.Add(entity);
context.SaveChanges();
}
}
}
I've not gone into detail about the dependency injection side of things as that wasn't part of the question but this should give you an idea of where to start