I have many multiple select dropdowns in my asp.net mvc application and am wondering what is the best way to handle transferring those values from my viewmodel to my model. The model is then saved to the database using ef6 (I'm using db first by the way to create my entities).
Currently one of my viewmodels looks something like this:
public class someviewmodel{
public string[] selectedIds
public IEnumerable<SelectListItem> SelectValues
//other properties
}
I decided to create a partial model class and add the selectedIds to it like:
public partial class somemodel{
public string[] selectedIds
//other properties
}
My model is then passed to my service layer:
public class someservicelayer{
public int InsertSomething(somemodel model){
//do stuff
if (model.selectedIds.Length != 0){
model.SelectValues = _context.SelectValues
.Where(b => model.selectedIds.Contains(b.Id.ToString())).ToList();
}
}
}
It feels wrong that I have to add a custom property in a partial class to my model. Is there a better way of handling this?
Related
I have various viewmodels that have properties that must be populated. For example, imagine a database table full of countries. I have a create user page, and one of the properties on the viewmodel is List<string> Countries.
Originally I populated this in a parameterless constructor, ie.
public CreateUserViewModel()
{
this.Countries = new CountryManager().GetCountries();
}
But I read this is a bad practice, and I should pass them in.
public CreateUserViewModel(IEnumerable<string> countries)
{
this.Countries = countries;
}
But in my post, this data is lost, and if validation fails it redirects to the view, but then the countries property is null.
I am wondering how I should be repopulating this value. Manually putting some code into the controller post method seems bad, eg.
[HttpPost]
public ActionResult CreateUser(CreateUserViewModel vm)
{
if (Model.IsValid)
{
new UserManager().CreateUser(vm);
}
else
{
vm.Countries = new CountryManager().GetCountries();
return View(vm);
}
}
I am struggling to google what is probably a very common question. Any ideas?
The rationale behind avoiding parameterless constructors is for inversion of control. The logic in this case would be that Countries is a dependency and by externalizing that dependency (so that it is inject into the class, instead), you make your class less brittle and more open to extension.
However, I would argue that doesn't apply actually in your scenario, because Countries is not really a dependency of your class, but rather of your view. The view model is there to serve the view and is somewhat closed and unextensible anyways as a result. In other words, do follow inversion of control for things like services, repositories, utility classes, etc., but for view models, it's not really necessary or important.
Anyways, here's how I handle this type of thing:
public class FooViewModel
{
...
// Countries is not initialize by a constructor
public IEnumerable<SelectListItem> Countries { get; set; }
}
Then in your controller:
public class FooController : Controller
{
internal void PopulateCountryChoices(FooViewModel model)
{
// fetch countries
model.Countries = countries.Select(m => new SelectListItem
{
Text = m.Name,
Value = m.Id.ToString()
});
}
public ActionResult Bar()
{
var model = new FooViewModel();
PopulateCountryChoices(model);
return View(model);
}
[HttpPost]
public ActionResult Bar(FooViewModel model)
{
if (ModelState.IsValid)
{
// save and redirect
}
PopulateCountryChoices(model);
return View(model);
}
}
Instead of populating this static data in model, We can populate Dropdownlist values in the view itself -
#Html.DropDownListFor(model => model.State,
new SelectList(Utils.GetCountries()),
"value",
"text",
2)
Where Utils is a Helper class which returns all the countries.
This way of populating all the static data (I mean all options of Dropdownlist or Listbox etc) will be taken over by the View, which makes model to be free from holding this data.
Hi I have model class which is written in MVC.I am using Ef database first approach. In model class I have some queries which deals with database. I have following questions :
1) Is it right way to use database related queries in Model and call that in controller or view?
2)If yes where I should call this model? In Controller or in view ??
3)How I should call this model? Say for example I have class called class1.cs in model.How I should call this model?
Your model contains classes that define the different objects troughout your project. This includes properties with their basic information and methods to perform actions on this object.
1)
Do you really need queries? Why not use the Entity Framework to do it for you? Create the mapping for your domain classes (either trough annotations or fluent api) and use the DbContext to retrieve and save the data stored in your database
2)
Ideally people create repositories that are injected into your controllers (Dependency Injection). These repositories can for example contain something like GetPersonById(int id). Inside this method there would be two things:
Perform an action on the domain object
Save it to the DbContext
For example:
public void Subscribe(int userID, Show show) {
var user = GetUserByID(userID);
if (!user.IsSubscribedTo(show.ShowID)) {
user.Subscribe(show);
_dbContext.SaveChanges();
}
}
Controller -> Method call in repository -> Perform action on corresponding domain object -> Save changes to the database
If you need something that doesn't require an object mutation, it's even more simple:
public User GetUserByID(int id) {
return _dbContext.Users.FirstOrDefault(x => x.ID == id);
}
3)
Trough repositories (see above). Your DbContext will have a bunch of DbSets that contain objects that correspond with every data entry in your database. Trough repositories you can work with these objects and manipulate them. When you call the DbContext.SaveChanges() method, it will look at what has changed in these lists and commit the changes to your database.
Repository example:
class User {
public int ID { get; set; }
public string Name { get; set; }
}
class DatabaseContext : DbContext {
public DbSet<User> Users { get; set; }
}
public interface IUserRepository {
User GetUserByID (int id);
bool UsernameExists (string name);
}
public class UserRepository : IUserRepository {
private DatabaseContext _db;
public UserRepository(DatabaseContext db){
_db = db;
}
public User GetUserByID(int id) {
return _db.Users.FirstOrDefault(x => x.ID == id);
}
public User GetUserByUsername(string username) {
return _db.Users.FirstOrDefault(x => x.Name == username);
}
}
public class UserController : Controller {
private IUserRepository _userRepository;
public UserController(IUserRepository userRepository) {
_userRepository = userRepository;
}
public ActionResult Details(int id){
return View(_userRepository.GetUserByID(id);
}
}
// Ninject settings (install this extension, you want it):
private void AddBindings(){
kernel.Bind<DatabaseContext>().ToSelf().InSingletonScope();
kernel.Bind<IUserRepository>().To<UserRepository>().InRequestScope();
}
You could use some sort of Unit Of Work pattern which you inject in your controller constructor using an inversion of control container (IOC), for instance autofac.
Your unit of work class could hold a reference to repositories, where you would query/insert your data.
Roughly;
public class BackendController : Controller
{
private UnitOfWork _worker;
public BackendController(UnitOfWork worker)
{
this._worker = worker;
}
public ActionResult Admin()
{
var items = _worker.MyRepository.GetAll();
return View(items);
}
}
public class UnitOfWork
{
private ContentRepository _contentRepository;
public UnitOfWork()
{
}
public ContentRepository MyRepository
{
get
{
if (_contentRepository != null)
return _contentRepository;
else
return _contentRepository = new ContentRepository();
}
}
}
public class ContentRepository
{
// holds an object context and methods to retrieve and put data (EF or similar)
}
You would have to register your instance with the IOC container in global.asax, application_start for example, something like this (Using autofac as IOC):
UnitOfWork worker = new UnitOfWork();
var builder = new ContainerBuilder();
builder.RegisterControllers(Assembly.GetExecutingAssembly());
builder.RegisterInstance(worker).SingleInstance();
var container = builder.Build();
...
1) Is it right way to use database related queries in Model and call that in controller or view?
I would recommend not directly accessing the database in your model classes, as you have to remember that MVC is strictly a presentation layer pattern. If you do put your database access logic in your model classes, then you will not be able to have any other client use this functionality, such as a web service. Instead have logic that translates your business objects, defined outside of your ASP.NET MVC project, into your ASP.NET MVC model classes.
This is where the power of n-tier architecture shines, if you create a business and data-access layer, then I could write an ASP.NET MVC front-end, WebForms front-end, WPF front-end, WinForms front-end and all of them could access data using the same service. By putting the logic into the ASP.NET MVC model classes, then you are effectively forcing any other client to duplicate that logic again in their classes.
I've been using the repository pattern described in Bob Cravens blog to create my application, but I'm a bit new and still finding my way around it. I want to inject my DataService object into the constructor of my ViewModel so I can create a SelectList object, and create a drop down box in my view. However I can't seem to get the bindings to work, every time I create the ViewModel it looks for / executes the parameterless constructor! I've tried various ways using answers here on SO but to no avail. Help would be greatly appreciated.
ViewModel:
public class ServerCreateViewModel
{
public SelectList Companies { get; private set; }
public ServerCreateViewModel()
{
}
public ServerCreateViewModel(DataService _dataService)
{
Companies = new SelectList(_dataService.Companies.All(), "Id", "CompanyName");
}
Ninject module:
Bind<DataService>().ToSelf()
.InRequestScope();
var _dataService = Kernel.Get<DataService>();
Bind<ServerCreateViewModel>()
.ToSelf()
.WithConstructorArgument("_dataService", _dataService);
//Bind<ServerCreateViewModel>()
// .ToSelf()
// .WithConstructorArgument("_dataService", ctx => ctx.Kernel.Get<DataService>());
Controller:
public ActionResult Create(ServerCreateViewModel viewModel)
{
return View(viewModel);
}
You shouldn't be doing that!
View Models (all models, in fact) should be just buckets with some data. They should not depend on any business logic, services, etc.
It is controller's responsibility to populate models and pass them to views.
public class ServerCreateViewModel
{
public SelectList Companies { get; private set; }
}
public ActionResult Create()
{
var viewModel = new ServerCreateViewModel
{
Companies = new SelectList(_dataService.Companies.All(), "Id", "CompanyName")
};
return View(viewModel);
}
DataService should be injected into the controller, not view model.
I want a way to separate the loading of reference data into a view model from the controller. At the moment I have a view model with a property for the selected value and the reference data:
public IEnumerable<SelectListItem> DayTypes { get; set; }
public int DayTypeId { get; set; }
and the data is populated from the relevant repository in the controller action:
model.DayTypes = _dayTypeRepository.GetAll().ToSelectList(d => d.Description, d => d.Identifier.ToString());
I would like to change this because it pollutes the controller with lots of repositories and code that is not core to its concerns. All of these dependencies make unit testing the controller a pain.
One possible approach to solving this would be to make the view model class do the loading which would require a custom model binder to instantiate them using the IoC container to provide the repository dependency. Is this a good option?
Another approach that I think would be good is hinted at in CodeCampServer but is incomplete and commented out involving attributes on the field in the view model:
[SelectListProvided(typeof(AllDaysSelectListProvider))]
public IEnumerable<SelectListItem> DayTypes { get; set; }
however I am struggling to figure out how this could be implemented in a way that would not require some major replumbing of the MVC framework.
How do you solve this problem?
EDIT: I want to keep with strongly typed views and avoid stuffing the data into view data.
FURTHER EDIT: I would also like a solution that is ideally model independent, by which I mean if the same reference data is needed by multiple view models this can be achieved with a single piece of code. Matt's approach is interesting but is tightly coupled to the view model.
I would use a service layer which would return me a POCO object that I would map to a view model. So my controller action would look like this:
public ActionResult Index(int id)
{
var model = _service.GetModel(id);
var viewModel = Mapper.Map<Model, ViewModel>(model);
return View();
}
I also like using action filters to avoid the mapping code all over again so:
[AutoMap(typeof(Model), typeof(ViewModel))]
public ActionResult Index(int id)
{
var model = _service.GetModel(id);
return View(model);
}
This way only the service talks with the CRUD repositories and the controller talks to the service and the mapping layer.
You could write a new ActionFilter that you can decorate an action method with; this action filter will load the reference data into the viewdata, which you can access from your view.
There is more on action filters here.
EDIT: Based on the users comments, this now includes a strongly typed option.
Firstly, you need to create the SharedViewModel to contain the shared data.
public class SharedViewModel
{
public List<string> Days { get; set; }
public List<string> Months { get; set; }
public List<string> Years { get; set; }
}
Next, we create the view model to be used by the Index view, which uses this shared view model.
public class HomeViewModel
{
public string ViewName { get; set; }
public SharedViewModel SharedViewModel { get; set; }
}
The next step is important, it implements an action filter called SharedData(), which will apply the shared data.
public class SharedDataActionFilter : ActionFilterAttribute
{
public override void OnActionExecuted(ActionExecutedContext filterContext)
{
var currentModel = ((HomeViewModel) filterContext.Controller.ViewData.Model);
currentModel.SharedViewModel = new SharedViewModel
{
Days = new List<string> {"Mon"},
Months = new List<string> {"Jan"},
Years = new List<string> {"2011"}
};
base.OnActionExecuted(filterContext);
}
}
At the moment, it just applies the whole shared data, but you can added parameters into the method to be selective.
When the action has been executed, this method takes the current model and adds the shared data.
Here is the controller action.
[SharedDataActionFilter]
public ActionResult Index()
{
return View("Index", new HomeViewModel { ViewName = "HomePage" });
}
You can access the data like any other strongly typed view, and the shared data wont affect the data already in the model (in this case "ViewName"). You can also use action filters across controllers, and globally across the site with mvc 3.
Hope this helps, Matt.
I am just getting into .NET MVC2 (.NET in general even) and I am having a hard time getting familiar with the "flow" of things. The MVC framework, I get.. for the most part. The part that I am getting tripped up on is applying standard programming practices to .NET MVC.
For example
public ActionResult Index()
{
var dataContext = new SiteContentDataContext();
var data = from c in dataContext.SiteContents where c.Slug == "home-page" select c;
// call/return getMainNav()
// call/return getSubNav()
return View(data);
}
public ActionResult SiteContent(string strSlug)
{
var dataContext = new SiteContentDataContext();
var data = from c in dataContext.SiteContents where c.Slug == strSlug select c;
// call/return getMainNav()
// call/return getSubNav()
return View(data);
}
private void getSubNav()
{
// get subnav records from db.
// return subnav records.
}
private void getMainNav()
{
// get main nav records from db.
// return main nav records.
}
The Index and SiteContent view are identical except for the fact that the Index view uses a different master page. Both views have a subnav and a main nav that will be dynamic content from a database.
The question, finally, is how would I go about populating the getSubNav and getMainNav functions and second, how would I return that data to the view properly?
Look into ViewModel objects, objects you create whose purpose in life is to carry data to and from your Views. The Models folder created for you by default in a new MVC project would hold exactly those classes.
You have options besides the ViewModel object methodology, but none are as clean. (The ViewData dictionary is around to help but it's not intended to be the primary means of providing data to your views.) Here's an example of how to set the Model property of the ViewData object to an instantiated, populated viewmodel instance:
public ActionResult SiteContent(string strSlug) {
SiteContentVM model = new SiteContentVM();
SiteService siteService = new SiteService();
model.Slug = siteService.GetALittleSlimyCreature(strSlug);
model.List1 = siteService.GetList1();
model.List2 = siteService.GetList2();
ViewData.Model = model;
return View();
}
You can now create a strongly typed view (complete with intellisense) to reference any properties of your ViewModel object instance from within your view simply through the Model property:
<% foreach (var item in Model.List1) { %>
<% Html.Encode(item.StringField) %> <!-- <= writing a property -->
<% Html.RenderPartial("PartialNameHere", item); %> <!-- <= the equivalent of a usercontrol -->
<% } %>
As you see above the process of getting data from the database does not change for MVC. You do it just as you would in a normal webforms project. (...usually this involves instantiating a business logic or service class of some sort rather than actually writing the code in the MVC project.)
Enjoy MVC!
You should look into DDD and TDD for ASP.NET MVC. For the looks of it you seem to be using Linq To Sql. I'm going to try to explain in a few words what I do to accomplish a good architecture.
Architecture
DB Context
Domain Model
Repository Pattern
It's good practice not to tie your Database Context with your Controllers. What you want to do is have your Controllers call your Repository, which in turn will return your Model. Now here's the tricky part you must convert the DB Context Objects into your Model Objects.
Imagine you have an Products table which Linq To SQL will give you as the Products Class.
That Products Class is part of the DB Context and what you want to do is alienate your context, in fact your Controllers won't even know it exists.
Why would I need a Model when I have Linq To SQL?
Well for starters LTS will regenerate all Objects everytime you change your Database meaning you wont have the ability to make change to the DB Context. And also you want to be able to use ASP.NET MVC 2 Annotations for validation and more.
Now create a Products Class for your Model
namespace MvcApplication.Models
{
public class Product
{
public int Id { get; set; }
[Required]
[StringLength(10)]
public string Name { get; set; }
[Required]
public string Description { get; set; }
[DisplayName("Price")]
[Required]
[RegularExpression(#"^\$?\d+(\.(\d{2}))?$")]
public decimal UnitPrice { get; set; }
}
}
Now you see this Class is part of the Model totally disconnected from the DB Context. Now what we do next is create our Repository Class.
namespace MvcApplication.Repository
{
public class AppRepository {
DbContext _context = new DbContext();
public IQueryable<Products> GetProducts()
{
return from p in _context.Products
select new Product {
Name = p.Name,
UnitPrice = p.UnitPrice
}
}
}
}
Now in your Controller you just call GetProducts();
public ActionResult SiteContent(string strSlug)
{
var repository = new AppRepository();
return View(repository.GetProducts());
}
Pretty isn't it.
You can use AutoMapper to map your DB Context objects to your Model objects.
http://automapper.codeplex.com/
Well ,,, i think what you are looking for here is Partial Views.
You can embed the MainNav & SubNav Views into your SiteContent View.
here's how this goes.
create your MainNav & SubNav as partial views.
in your SiteContent view use the Html.RendarPartial Method to include the other two views.
<%= Html.RenderPartial("MainNav", Model); %>
<%= Html.RenderPartial("SubNav", Model); %>
Now to the remaining part about how to get the data to the MainNav & SubNav views. Now is a good time to get familiar with ViewModels. View models are nothing but classes with some properties that you want to give to a view to display.
In your case i would create 3 view models.
SiteContentViewModel contains the content that will be displayed in your page.
MainNavViewModel contains the data that will be displayed insdie the MainNav.
SubNavVIewModel contains the data that will be displayed insdie the SubNav.
then i would include the MainNavViewModel & SubNavVIewModel inside the SiteContentViewModel.
(if you are sure that every SiteContent View will have a MainNav & a SubNav )
Now it's up to you to fill each view model with that data that you need.
here's how the code will look like.
public class SiteContentViewModel {
public MainNavViewModel MainNav { get; set;}
public SubNavVIewModel SubNav { get; set;}
// Any Other Data Needed In The SiteContent View (ex. PageTitle)
}
public class MainNavViewModel {
// Any Data Needed In The MainNav View
}
public class SubNavVIewModel {
// Any Data Needed In The SubNav View
}
Now back to the Partial Views ,,, using the View Models we created we can include the partials like this.
<%= Html.RenderPartial("MainNav", Model.MainNav); %>
<%= Html.RenderPartial("SubNav", Model.SubNav); %>
one important thing is to make our views strongly typed.
SiteContent view of type SiteContentViewModel
MainNav view of type MainNavViewModel
SubNav vIew of type SubNavViewModel
and in your SiteContent action method you will do something like this
// Initialize the ViewModels.
SiteContentViewModel model = new SiteContentViewModel();
model.MainNav = new MainNavViewModel();
model.SubNav = new SubNavVIewModel();
// Get Data From DB and set the properties that you created in your view models.
// examples.
model.PageTitle = // some data from db.
model.MainNav.(Some Property) = // some data from db.
model.SubNav.(Some Property ) = // some data from db.
return View(model);
hope that helps ... for more information you can see this link