I am developing an MVC3 "movie list" application containing several "sites" depending on the request hostname.
I am trying to use a strongly typed ViewModel like this (examples are simplified to get to the essence of the question):
class ViewModelBase
{
public int siteId { get; private set; }
public ViewModelBase(DbContext db)
{
siteId = <here I want to make a db-lookup based on the request hostname> <== This is my problem
}
}
class MoviesIndexViewModel : ViewModelBase
{
public List<Movie> movies { get; private set; }
public MoviesIndexViewModel(DbContext db) : base(db)
{
movies = db.Movies.where(m => m.SiteId == siteId).ToList();
}
}
An my controller would then just do this:
public class MoviesController : Controller
{
public ActionResult Index()
{
var model = new MoviesIndexViewModel(new MySpecialDbContext());
return View(model);
}
}
Question is: How will I get the "request host header" into the code line shown above? I know how to make the actual DB-lookup, but can I just access any request parameters here? Or should I supply something through parameters to the constructor?
I would not use Dbcontext in my view models. Read about Separation of concerns
Instead, use OnResultExecuting in your BaseController to add the common data:
protected override void OnResultExecuting(ResultExecutingContext filterContext)
{
var baseModel = filterContext.Controller.ViewData.Model as YourCustomModel;
if (baseModel != null)
{
// call a repository or whatever to add information to the model.
}
base.OnResultExecuting(filterContext);
}
Update
yes. The controller is the glue between the "model" (repositores, webservices or any other data source) and the view. The ViewModel is just an abstraction to move away logic from the view.
Here is the three main reasons you should use a view model:
http://blog.gauffin.org/2011/07/three-reasons-to-why-you-should-use-view-models/
And an alternative approach to handle common view data: http://blog.gauffin.org/2011/09/getting-information-into-the-layout-without-using-viewbag/
Related
From what I can tell, ASP.Net Core performs model state validation before calling the relevant controller action method. This means that code in the action method isn't given an opportunity to add data to the model before it is validated.
What is the ASP.Net Core way of giving a view model access to additional, non-user-submitted data prior to validation?
Example
What I'm trying to do (doesn't work).
The view model's Validate method expects data to be in ValidOptions. However, since validation occurs before the controller can set this property, validation causes the view model to throw an ArgumentNullException.
// From the Controller
[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Process([Bind("SelectedId")]ViewModels.Import details)
{
// data needed for validation
details.ValidOptions = await service.ImportTypes.ToListAsync();
if (ModelState.ValidationState != ModelValidationState.Valid) {
// ...
}
}
// From ViewModels.Import
public IEnumerable<Option> ValidOptions { get; set; }
public int SelectdId {get; set; }
public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
{
// throws ArgumentNullException because ValidOptions hasn't been set when this is executed
var option = ValidOptions.Single(t => t.Id == SelectdId);
//...
}
Probably many ways to skin a cat here. But the easiest for you is probably custom model binders. It's a way to "supplement" or change the binding of your model before it hits the controller. I will say that some see it as extremely bad practice to call an external service/repository at the point of model binding, but it does work and can come in handy.
You need to implement a class that inherits from IModelBinder.
public class MyViewModelBinder : IModelBinder
{
public Task BindModelAsync(ModelBindingContext bindingContext)
{
//Bind here. Including calling external services if you want.
}
}
Then you need to implement a provider, this essentially says "when" to bind.
public class MyViewModelBinderProvider : IModelBinderProvider
{
public IModelBinder GetBinder(ModelBinderProviderContext context)
{
if (context.Metadata.ModelType == typeof(MyViewModel))
return new MyViewModelBinder();
return null;
}
}
In your configure method of your startup.cs, you need to add the provider to the ModelBinderProviders list.
public void ConfigureServices(IServiceCollection services)
{
// Add framework services.
services.AddMvc(config =>
config.ModelBinderProviders.Add(new MyViewModelBinderProvider())
);
}
Further Documentation :
http://dotnetcoretutorials.com/2016/12/28/custom-model-binders-asp-net-core/
http://intellitect.com/custom-model-binding-in-asp-net-core-1-0/
I don't think the official documentation has an article on custom model binders yet unfortunately.
Is it possible to pass an ViewModel object to WebApi controller action instead of separate params?
Instead of using:
public class ContactsController : ApiController
{
public IEnumerable<Contact> GetContacts(string p1, string p2)
{
// some logic
}
}
I would like to use:
public class ContactsController : ApiController
{
public IEnumerable<Contact> GetContacts(TestVM testVM)
{
// some logic
}
}
public class TestVM
{
public string P1 { get; set; }
public string P2 { get; set; }
}
This doesn't seem to work for me. When I call /api/contacts/?P1=aaa&P2=bbb the testVM object doesn't get populated (null).
Also, I would like the TestVM to have valdiation attribtues defined and use ModelState.IsValid in my API controller.
Unless told otherwise WebApi will deserialise complex models using the content/body of the request. To tell WebApi to use the Url to construct the model you need to specify the [FromUri] attribute:
public IEnumerable<Contact> GetContacts([FromUri]TestVM testVM)
{
// some logic
}
I know it's kind of late to post another answer but I thought it could be useful for anyone who uses .net core as a web API service
public IEnumerable<Contact> GetContacts([FromQuery]TestVM testVM)
I want to create a wrapper class so that all queries should not be in controller. Currently select queries are placed in Controller. But I want to create another layer for abstraction.
I already created a viewmodel class. But wrapper class is something else.
How do I do that?
I don't do any queries directly in my controllers. I have a service layer which my controller would call, and each service layer would do a call to the repository to insert, update or delete data or bring back data.
The sample code below uses ASP.NET MVC3 and Entity Framework code first. Lets assume you want to bring back all the countries and use it for whatever reason in your controller/view:
My database context class:
public class DatabaseContext : DbContext
{
public DbSet<Country> Countries { get; set; }
}
My country repository class:
public class CountryRepository : ICountryRepository
{
DatabaseContext db = new DatabaseContext();
public IEnumerable<Country> GetAll()
{
return db.Countries;
}
}
My service layer that calls my repository:
public class CountryService : ICountryService
{
private readonly ICountryRepository countryRepository;
public CountryService(ICountryRepository countryRepository)
{
// Check for nulls on countryRepository
this.countryRepository = countryRepository;
}
public IEnumerable<Country> GetAll()
{
// Do whatever else needs to be done
return countryRepository.GetAll();
}
}
My controller that would call my service layer:
public class CountryController : Controller
{
private readonly ICountryService countryService;
public CountryController(ICountryService countryService)
{
// Check for nulls on countryService
this.countryService = countryService;
}
public ActionResult List()
{
// Get all the countries
IEnumerable<Country> countries = countryService.GetAll();
// Do whatever you need to do
return View();
}
}
There are lots of info on the internet on how to get you data and display it, inserting, editing, etc. A good place to start is at http://www.asp.net/mvc. Work through their tutorials, it will do you good. All the best.
I am creating an ASP.NET MVC3 restful web service to allow reports to be uploaded from a set of servers. When a new report is created, I want the client app to do a PUT to
http://MyApp/Servers/[ServerName]/Reports/[ReportTime]
passing the content of the report as XML in the body of the request.
My question is: how do I access the content of the report in my controller? I would imagine that it is available somewhere in the HttpContext.Request object but I am reluctant to access that from my controller as it is not possible(?) to unit test that. Is it possible to tweak the routing to allow the content to be passed as one or more parameters into the controller method? The outcome needs to be RESTful, i.e. it has to PUT or POST to a URL like the one above.
Currently my routing is:
routes.MapRoute(
"SaveReport",
"Servers/{serverName}/Reports/{reportTime",
new { controller = "Reports", action = "Put" },
new { httpMethod = new HttpMethodConstraint("PUT") });
Is there any way to modify this to pass content from the HTTP request body into the controller method?
The controller method is currently:
public class ReportsController : Controller
{
[HttpPut]
public ActionResult Put(string serverName, string reportTime)
{
// Code here to decode and save the report
}
}
The object I am trying to PUT to the URL is:
public class Report
{
public int SuccessCount { get; set; }
public int FailureOneCount { get; set; }
public int FailureTwoCount { get; set; }
// Other stuff
}
This question looks similar but doesn't have any answer.
Thanks in advance
Seems like you just need to use the standard ASP.NET MVC model binding capability with the slight wrinkle that you would doing an HTTP PUT instead of the more common HTTP POST. This article series has some good samples to see how model binding is used.
Your controller code would then look like:
public class ReportsController : Controller
{
[HttpPut]
public ActionResult Put(Report report, string serverName, string reportTime)
{
if (ModelState.IsValid)
{
// Do biz logic and return appropriate view
}
else
{
// Return invalid request handling "view"
}
}
}
EDIT: ====================>>>
Jon added this code to his comment as part of the fix so I added it to the answer for others:
Create a custom ModelBinder:
public class ReportModelBinder : IModelBinder
{
public object BindModel(
ControllerContext controllerContext,
ModelBindingContext bindingContext)
{
var xs = new XmlSerializer(typeof(Report));
return (Report)xs.Deserialize(
controllerContext.HttpContext.Request.InputStream);
}
}
Modify the Global.asax.cs to register this model binder against the Report type:
ModelBinders.Binders[typeof(Report)] = new Models.ReportModelBinder();
I just started using View & Domain model design in my MVC web app but got the question where to perform calculations and other View related actions. I will try to give example below.
My Domain Model (Linq2Sql)
public class Product
{
public int Id;
public string Name;
}
The View Model with new UserCount property which I would like to calculate.
public class ProductViewModel
{
public int Id;
public string Name;
public int UserCount;
}
My controller action looks like
public ActionResult _SelectionClientSide_Products()
{
IQueryable<Product> products = _repository.GetProducts(true);
var model = Mapper.Map<IEnumerable<Product>, IEnumerable<ProductViewModel>>(products);
return View(model);
}
I query for data using repository method and get IQueryable<Product> and map it to ProductViewModel list. But I also need to perform another query operation to count users for every queried product and assign all values to ProductViewModel. What design I should follow to achieve this?
The relationship between tables
Products -> Orders - > Users
EDIT
I have decided to remove AutoMapper because it gives more problems than benefits and created my own Builder which contain everything what I need. I make field assign and also add calculation.
public ActionResult _SelectionClientSide_Products()
{
Data = new ProductViewModelBuilder(_repository).Build();
return View(Data);
}
namespace PC.Models
{
public class ProductViewModel
{
public int Id { get; set; }
public string Name { get; set; }
public int UsersCount { get; set; }
}
public class ProductViewModelBuilder
{
private readonly IDataAccess _repository;
public ProductViewModelBuilder(IDataAccess repository)
{
_repository = repository;
}
public IQueryable<ProductViewModel> Build()
{
return _repository.GetProducts().Select(p=> new ProductViewModel
{
Id = p.Id,
Name = p.Name,
UsersCount = _repository.CountUsers(p.Id)
});
}
}
}
In my opinion, by the time your Controller has begun it's model setup, there should be no more "logic" or talking to the model. Having a "builder" which queries the model again is bad practice. Not really "breaking" the MVC pattern, but still bad practice. Your ViewModel has a dependency on your DAL. Bad bad boy. :)
If you have to run another query, well that should be encapsulated in the original query. Instead of calling _repository.GetProducts, call a different method which not only gets the products, but get's the count as well. Create a DTO if necessary.
Then your controller should look like:
public ActionResult _SelectionClientSide_Products()
{
var someDto = _repository.GetProductsAndUserCount(true);
var model = Mapper.Map<IEnumerable<SomeDto>, IEnumerable<ProductViewModel>>(someDto);
return View(model);
}
Personally i go for generic repositories over specialized ones, as i don't want a IProductRepository interface with 50 signatures. I opt for LINQ IEnumerable<T> extensions (aka "pipes and filters") which allows complex queries to be built and remain in my domain.
So my version of the above would be:
public ActionResult _SelectionClientSide_Products()
{
var someDto = _productRepository.Find().WithSomeCondition(true).ToSomeDto();
var model = Mapper.Map<IEnumerable<SomeDto>, IEnumerable<ProductViewModel>>(someDto);
return View(model);
}
On a side note, why do you say AutoMapper causes you more problems that benefits? AutoMapper has saved me tons and tons of repetitive code. If you know how to use it properly, it's your best friend. Hands down the most important NuGet package in my current application.