I have been scouring forums and repository pattern blogs for some clear direction on how I should be coding my project and I'm stuck. Any help or guidance from you guys would be much approciated :)
I started my project as EF5 MVC4 Razor Code First and decided to use MVCScaffolding to generate all my controllers, views and repositories. This was my first project with these technologies, I was just told that this was how the team was doing it now (but the previous developers did model first and hand coded their contexts).
SO, all is great, we're coding a bunch of screens, but one of our screens is a complex one that involves many models/sub modlels (ie/ Object model has FKs to Responses, Attachments, Reviewers, etc...). The user adds a bunch of data, selects one or more reviewers, adds 0 or more attachments. Then they hit Save!
Now my big problem is that I want to save all this data as one transaction, and if something fails on one of the children models (ie/ attachments) the transaction will roll back. However, the way the MVCScaffolding repositories are created, each model has it's own instance of DB Context and it's own Save. And the controllers accept each unique repository as parameters for loading the screen data. Another thing to note is for this screen we are using a ViewModel to load the data, and then wrote custom mappers to map back to the different models for saving. We can save each piece separately, and possibly the solution is just to wrap TransactionScope around my save, but I also want to reduce the number of calls to the db, as each repository save does a call.
I thought I could add code to the parent repository for a UnitsOfWork type save that would add/edit all the child obejcts in one context object, but that seems like a hack more than anything, and I want to code this properly.
One of the other projects here just made a custom DB context and all Save methods were in that class, is that the best way to do it? Another dev did code first but hand coded all his Save methods. None of them are in a standard place and he is using TransactionScope with a DBContext inside (is that overkill or does DBContext not handle transactions)?
Since I'm so new to this, I need help and no one I work with seems to agree on a proper method. I'm not sure if my model is wrong for an "MVC App" since I'm such a database heavy thinker.
Below is a sample of my models, any guidance is appreciated. Thanks :)
public class Anomaly
{
[Key]
public int AnomalyId { get; set; }
public string Subject { get; set; }
public int PlantId { get; set; }
[ForeignKey("PlantId")]
public virtual Plant Plant { get; set; }
public DateTime? ReviewByDate { get; set; }
public virtual ICollection<AnomalyReviewer> AnomolyReviewers { get; set; }
public virtual ICollection<AnomalyAttachment> AnomalyAttachments { get; set; }
}
public class AnomalyAttachment
{
[Key]
public int AnomalyAttachmentId { get; set; }
public int AnomalyId { get; set; }
[ForeignKey("AnomalyId")]
public virtual Anomaly Anomaly { get; set; }
public string FilePath { get; set; }
public string FileName { get; set; }
public string FileExtension { get; set; }
public string Notes { get; set; }
}
ps. that is just a sample... thanks!
Just create a class 'Master' that inherits from Controller.
Then write all your queries there as in public User GetUserById(Int32 id)
Finally create a function that does a call to the private!! implementation of DbContext.
I would usually give that function a enum of SystemEvents so i've got a reference of whats happening if something would fail... of course you would need to write your own notificator or model to record your own errors into the database for personal testing...
ive done all this because I can write all my code and found out that Repository Pattern is overkill most of the time if you actually think about it.
Related
I'm working with Entity Framework with a database-first approach. I already defined the model inside my application. Now I'm working with controllers and views. I used scaffolding in order to create controllers. Now I want to create rows.
Let's say I want to create employees, and let's say the DBA and EF made this possible:
public partial class TBL_EMPLOYEE
{
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
public TBL_EMPLOYEE()
{
this.TBL_EMPLOYEE = new HashSet<TBL_EMPLOYEE>();
}
public int EMPLOYEE_ID { get; set; }
public String CO_WORKER_NUMBER { get; set; }
public string NAME { get; set; }
public string LAST_NAME { get; set; }
public string SALARY { get; set; }
public string PHONE_NUMBER { get; set; }
public string EMAIL { get; set; }
public string { get; set; }
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
}
Now, I need a view to create an employee, let's call this view VIEW 1
In this view, the user only needs to specify name and last name values. Both are required.
Now, in this VIEW 1 case I could use the following data annotations attributes in the same class, that'd be:
[Required]
public string NAME { get; set; }
[Required]
public string LAST_NAME { get; set; }
Now, let's go to the next case. I need another View, let's call this VIEW 2
In this one, the user needs to specify all values for all attributes. All of them are required except for name and last name.
THE REAL QUESTION
How can I use the same model class for both views? The example above here might seem a bit silly and trivial validations but I've been in bigger projects where entities are bigger and the idea of having different ViewModel classes is just so much work.
I've stumbled upon this in my .NET developments, to the point I had to create a ViewModel class per view in order to be specific with what the user needs to input and their validation. Is this the only way?
To avoid duplicating models with minor variations, try this:
https://stackoverflow.com/a/18898112/6850962
Basically, create a base model with data annotations that apply in all situations (eg: DisplayName) and then extend the model for variations (eg: Required attribute).
If you are trying to use your Entity Framework entities approach, I wouldn't put validation attributes on those entities. I would either:
create separate distinct classes and then copy data from the EF entities to the models, and vice versa on update (either by writing the code explicitly, or using a tool like AutoMapper or many others). Then you can define the validation rules anyway you want. Unfortunately this approach does tightly couple validation to the model and thus model reuse may not be as possible.
Use a more fluid validation framework like FluentValidation (https://github.com/JeremySkinner/FluentValidation). The benefit to this is that you define an external class with the rules internal, which can be applied differently depending on the situation. The model may still need some indicator on the model itself to figure out which rules apply, but this is another functional approach to handling the scenario you describe.
For example: I need to display comments from Comments table in database.
So in DAL project I have POCO class:
public class Comments
{
public int CommentId { get; set; }
public string Author { get; set; }
public string Content { get; set; }
}
In BLL project I have class (DTO - data transfer object):
public class CommentsDTO
{
public int CommentId { get; set; }
public string Author { get; set; }
public string Content { get; set; }
}
So I get IEnumerable from DAL, convert to IEnumerable and return it to Web project.
In Web project I have class:
public class CommentsViewModel
{
public int CommentId { get; set; }
public string Author { get; set; }
public string Content { get; set; }
}
So in Web project I get IEnumerable from BLL, convert to IEnumerable and return it to view.
Is it correct? Because these classes have only different names.
It is certainly incorrect and you should not do this generally ad this just duplicates the code. You need different classes only when they differ. Suppose that you want to display a Comment in your web application and Comment is associated with User entity. Then, instead of sending 2 object separately you just create DTO class that combines properties of the two (like comment text and user name). Then sometimes you need to change the model in your web application to display data properly. For instance you want to display them in grid, and to do that properly you need to assign some attributes over properties and this is a good reason to create separate model in your web application. If you do not need to change your classes you should reuse existing ones. However even in your case changing CommentsViewModel a bit might be beneficial - usually you do not want user to see CommentId value (this is db internal thing) - so you can this field in [HiddenInput(DisplayValue = false)] so you could use Html.EditorForModel just to display editor panel. But this is your choice.
Creating each class for every layer is certainly beneficial for large projects. When I say large, I mean exceeding 5 developers with a application lifetime of 10 years. On large projects, the disadvantage of duplication becomes small compare to the benefit it provides.
For small projects, it is certainly overkill. The extra weight will slow you down with little or no benefit. Its like packing 7-day clothes on a 2 day hiking trip.
The larger the project, the more formal is your architecture.
With that said, here is my advice:
The Comment should be shared by the DAL and Business Layer.
If you don't have a "service layer", loose the DTO classes and map the Comment straight to the CommentViewModel. More about the service layer
I say Comment without "s" because only classes that represents collections should be named plural.
My understanding is that only one model can be passed to the view at a time. The problem with this that I see is that I am being forced to pass the Entity Framework model, and not any model that will manage housekeeping in the view. Here is what I mean:
You need to make a page that allows someone to submit Cars to the database. Along with the form fields (e.g. CarName, CarMake, CarYear) you also need a checkbox at the bottom of the page called "Remember Values" which when checked will "remember" the form values when the user clicks the Submit button at the bottom, so when they return all of their form data is still in the form fields. Needless to say, this Remember Values variable is not part of the Entity Framework model- it is just a housekeeping variable for use in the view.
How would you guys handle adding this checkbox? It feels like it should be part of the model, but I can't send two models to the view. Am I just looking at this issue wrong? What would you recommend?
.NET 4.5/MVC 5/EntityFramework 6
This is a good situation to be using ViewModels.
Build your ViewModels with all properties that you'd want to send/retrieve to/from your view. For example:
EF Entity
public class Car {
public virtual Guid Id { get; set; }
public virtual string Name { get; set; }
public virtual string Make { get; set; }
public virtual string Year { get; set; }
}
View Model
public class AddCarViewModel {
public Car Car { get; set; }
public bool RememberValues { get; set; }
}
Controller
public class CarController : Controller {
// Constructor....
public ActionResult Add() {
var vm = new AddCarViewModel();
return View(vm);
}
[HttpPost]
public ActionResult Add(AddCarViewModel vm) {
if (ModelState.IsValid) {
_carService.Save(vm.Car);
}
return View(vm);
}
}
Another good approach is to create Domain Transfer Objects, which are POCO classes to hold data that is transferred through the pipes. For example, in your business layer you may want to audit any changes to your Car model. So you may have properties like CreatedBy, CreatedDate, UpdatedBy, UpdatedDate, etc. (These properties are generally never displayed to the end-user but are important to store).
So you'd create the following classes:
public class Car {
public virtual Guid Id { get; set; }
public virtual string Name { get; set; }
public virtual string Make { get; set; }
public virtual string Year { get; set; }
public virtual User CreatedBy { get; set; }
public virtual User UpdatedBy { get; set; }
public virtual DateTime CreatedDate { get; set; }
public virtual DateTime UpdatedDate { get; set; }
}
public class CarDTO {
public Guid Id { get; set; }
public string Name { get; set; }
public string Make { get; set; }
public string Year { get; set; }
}
and you can use a library such as AutoMapper to map properties from Car -> CarDTO:
var car = _carService.GetCarById(id);
var carDTO = Mapper.Map<Car, CarDTO>(car);
This way, you can choose which properties you want exposed to your views by utilizing DTO's.
I always create an additional model that I can convert to and from between the EF model.
This additional model gets passed to the View and holds al the neccesary properties like CarName, Carmake, CarYear, Remember and probably most importantly, the Id of that particular object.
So when the user submits, this model gets passed to the Post method where you can extract all the required properties. You fetch the database model using the Id from your DbContext and update the properties with the values that were just passed through.
Technically you can send two models to the view, if the model is actually something like a Tuple:
#model Tuple<SomeEFModel, SomeViewModel>
Though that's kind of ugly. And if you're creating a view model anyway you might as well just make it a composite of the Entity Framework model. Something like:
public class SomeViewModel
{
public SomeEFModel EFModel { get; set; }
public string SomeOtherProperty { get; set; }
// other stuff...
}
Then just build an instance of that in the controller and send it to the model:
#model SomeViewModel
You could even just de-couple the EF model and the view model entirely, creating a custom view model that has everything for that view and then translating to/from that and the EF model at the controller level. Ultimately it comes down to what implementation looks cleaner and is easier to maintain, which can differ from one context to another.
Edit: Another option, if the models get unwieldy for whatever bits of the framework you're relying on, could be to separate your outgoing and incoming models. For pushing data to the view, you can use the composite view model above. But then when the data comes back from the view just use a normal Entity Framework model and a couple of additional parameters for your additional fields:
public ActionResult Edit(int id)
{
// build the view model with the EF model as a property
return View(someViewModel);
}
[HttpPost]
public ActionResult Edit(SomeEFModel model, string someOtherProperty)
{
// here you have an EF model from the view like normal
// plus the additional property (however many you need)
// you can even create a separate view model to collect the other properties
// as long as the names are well defined, the model binder should build both
}
First, you absolutely should NOT be passing your EF models directly to your view, and you should certainly NOT be posting directly to your EF models. This is essentially taking untrusted, unsanitized input and directly writing it to your data model with only bare minimal validation.
While this may work with simple models with no security or other ramifications, imagine a situation where you allowed a user to edit his profile information. Further, imagine that in his profile you also stored information relating to his subscription information. A specially crafted submit could alter his subscription information and give himself free access to your site, or worse...
Instead, you use view models. Apart from the security aspects, view models are good because other than in very simple CRUD style sites, your views requirements are typically different from your data models requirements. For instance, a particular field might be nullable in your data model, but you might want to make it required in your view. If you pass your model directly, then you can't do that easily.
Finally, Aggregate view models aggregate many different submodels to provide an overall model for the view, which is what you are getting at. You would then use a service layer, repository, or business logic layer to translate your view model to your data model, massaging data or applying logic as needed.
Here is the situation I am struggling with.
I have an Object Model:
public class MyModel
{
public string Prop1 {get; set;}
public string Prop2 {get; set;}
//etc
}
Then I have Object ModelView
public class MyModelView
{
public MyModel MyModelObject;
public SelectList PropToBeSelected1 {get; set;}
public SelectList PropTobeSelected2 {get; set;}
//etc
}
I have the MyModelRepository class as well that does the delete, update operations for MyModel.
All good and clear so far.
Question:
PropToBeSelected1 and PropTobeSelected2 are drop down lists whose contents come from the database. Should the methods retrieving these contents be put in my MyModelRepository? Or should I create another repository for ViewModel?
Thank you.
First you really don't want domian-ish objects in your viewModel. Your viewModel should be clean with only primitives (like strings, ints... etc). So I'd suggest using a AutoMapper to map your two string props to your viewModel.
With the select list, there are many ways to go about this but I can imagine if they are lists of properties then they are not actual entities, but value objects instead. In this case creating a repository for them is over kill and boarders bad design.
I'd put the 'get' of the property lists in your MyModelRepository. Something like
_myModelRepository.getProperties1For(myModel);
Then AutoMap again on to get your select list.
Edit:
Like #M.Radwan pointed out for complex domain models I'll make viewModels insdie viewModels for easy of mapping.
Domain Model--
public class User : Entity
{
public Address Address { get; set; }
}
public class Address
{
public string Street { get; set; }
public string Zip { get; set; }
}
would map to
public class DetailsViewModel
{
public int Id { get; set; }
public string Name { get; set; }
public AddressViewModel Address { get; set; }
public class AddressViewModel
{
public string Street { get; set; }
public string Zip { get; set; }
}
}
which in our experience has been the only reason to add any complexity to your viewModel. We will put SelectLists in our viewModel though but lately we've been using IEnumerables of inner viewModels and calling custom EditorFor or DisplayFor to turn them into a dropdown / list of checkboxes / radio buttons.
The answer is NO, you should not make any repository for them if you really need them with this view. so they probably are value objects as #jasonhooten said and they should connected to the main aggregate object that used by the repository
Finally I don't decide the ViewModel structure until I finish the view and make it working first and this why I founder and create DevMagicFake, by using DevMagicFake you will delay all decisions of the design regarding the structure of the ViewModel or the repository or how you will use service layer, all this will be delayed after full complete your view and make it working first as BDD (Behavior Driven Development) and TDD (Test Driven Development) so you can take the right decisions of the design and the object model itself
So I just create the action method as the following
public ActionResult List(MyModelView myModelView)
{
FakeRepository<MyModelView> repository = new FakeRepository<MyModelView>();
repository.Add(myModelView);
}
This fake repository will enable me to save and retrieve my whole model even it's a complex model until I finish and complete the whole view and make it working first, and then I start thanking on how the real design and the real repository should looks like, and do on
For more information about DevMagicFake and this approach see this link
DevMagicFake on CodePlex
I am creating a Web application using ASP.NET MVC, and I'm trying to use domain-driven design. I have an architecture question.
I have a WebControl table to store keys and values for lists so they can be editable. I've incorporated this into my business model, but it is resulting in a lot of redundant code and I'm not sure it belongs there. For example, in my Request class I have a property called NeedType. Because this comes from a list, I created a NeedType class to provide the values for the radio buttons. I'm showing just one example here, but the form is going to have probably a dozen or so lists that need to come from the database.
[edit, to clarify question] What's a better way to do this? Are these list objects really part of my domain or do they exist only for the UI? If not part of the domain, then they don't belong in my Core project, so where do they go?
public class Request : DomainObject
{
public virtual int RequestId { get; set; }
public virtual DateTime SubmissionDate { get; set; }
public virtual string NeedType { get; set; }
public virtual string NeedDescription { get; set; }
// etc.
}
public class NeedType : DomainObject
{
public virtual int NeedTypeId { get; set; }
public virtual string NeedTypeCode { get; set; }
public virtual string NeedTypeName { get; set; }
public virtual int DisplayOrder { get; set; }
public virtual bool Active { get; set; }
}
public class RequestController : Controller
{
private readonly IRequestRepository repository;
public RequestController()
{
repository = new RequestRepository(new HybridSessionBuilder());
}
public RequestController(IRequestRepository repository)
{
this.repository = repository;
}
public ViewResult Index(RequestForm form)
{
ViewData.Add("NeedTypes", GetNeedTypes());
if (form == null)
{
form = new RequestForm();
form.BindTo(repository.GetById(125));
}
}
private NeedType[] GetNeedTypes()
{
INeedTypeRepository repo = new NeedTypeRepository(new HybridSessionBuilder());
return repo.GetAll();
}
}
Create a seperate viewmodel with the data you need in your view. The Model in the M of MVC is not the same as the domainmodel. MVC viewmodels are dumb DTO's without behaviour, properties only. A domain model has as much behaviour as possible. A domain model with get;set; properties only is considered an anti-pattern called "anemic domain model". There are 2 places where most people put the viewmodels: in the web layer, close to the views and controllers, or in a application service layer.
Edit:
When you only need to display a list of all needtypes in the database and one request in your view, I would indeed create one viewmodel with the request and the list of needtypes as properties. I don't think a call to multiple repositories in a controller is a smell, unless you have a larger application and you might want a seperate application service layer that returns the whole viewmodel with one method call.
I think it might also be a good idea to follow the advise of Todd Smith about value object.
When the needtypes can be added or edited by users at runtime, needtype should be an entity. When the needtypes are hardcoded and only changed with new releases of the project, needtype should be a value object and the list of needtypes could be populated by something like NeedType.GetAll() and stored in the database by adding a column to the request table instead of a seperate needtype table.
If it comes from a list, then I'm betting this is a foreign key. Don't think about your UI at all when designing your domain model. This is simply a case where NeedType is a foreign key. Replace the string NeedType with a reference to an actual NeedType object. In your database, this would be a reference to an id.
When you're building your list of NeedType choices, you simply need to pull every NeedType. Perhaps keeping it cached would be a good idea if it doesn't change much.
Your NeedType looks like a value object to me. If it's read-only data then it should be treated as a value object in a DDD architecture and are part of your domain.
A lot of people run into the "omg so much redundancy" issue when dealing with DDD since you're no longer using the old Database -> DataTable -> UI approach.