I'm new to ASP.NET MVC and inherited a project that uses the technology.
Such Web project contains three folders: Views, Controllers and Model. As I understand it, the Model contains in fact your domain / business logic and is called by your controllers. The controllers themselves act as delegators between Views and Model.
Now, in a typical layered architecture, there should be no references in any project to the Web/UI project.
I find this quite confusing:
-> The UI contains the Model, which is - in an ideal world - based on "Domain Driven Design"-principles.
-> The layers on top of the UI (Services and DataAccess) cannot have a reference to the UI
How can you write efficient services and dataaccess layers if they do not know your model?
What am I missing here? Is the Web.Model different from "DDD" and should I still have a separate BL project? If that is the case, then what is the Web.Model supposed to contain?
I view the Model as a concept. You can have a completely separate project containing your Domain (your entities, your services etc.) and reference that in your "UI" project. In this scenario this will be your "Model".
This is what I typically do, In my Models folder I keep "ViewModels", which I use for Binding/Validation (for the UI).
For example, If I have an Employee but I don't necessary want to use all its properties (or for that matter different properties), I will create an EmployeeViewModel adjust it the way I want, I'll add validation (if required) and I'll pass it to my View.
This is by no means, "the right way"/"only way", but It worked for me in the past, and I thought I'll share (also, I'm pretty terrible in explanations, so I really hope this post makes sense, in case it doesn't or clarifications are needed - please let me know).
You necessarily do not need to have your model in the same project. You can ofcourse have those in different layers.
This is how i usually setup my projects
1) UI Project - This is an MVC Web application type project where i will have my controllers and it's views and other UI related stuff
2) Business Entities - This will be a class library type project where i will define my domain objects ( Ex : Customer). This mostly looks similar to how my DB schema looks like. These are usually just POCO's which represent my domain modal ( I use this for the CodeFirst Database generation).
3) Data Access - This will be another class library type project which has the data access classes. Usually my repository class/interfaces, my DBContext class and other data access classes will be in this project.
4) Tests - Unit tests for the project
Business Entities project has been added as a reference to the Data Access Project so that i can use those classes in my Data access code.
Business Entities and Data Access Projects are added as references in UI Project. I would call the data access methods from my Controllers/ Service classes.
You may also add a Service/Business logic layer between your controller's and Data access layer as needed.
I have few ViewModel classes also inside my UI project ViewModels folder. I use this for some screens where i have to show data from multiple domain objects. I have a mapping/service class which maps the domain object to view model object. If your project is bifg, you may keep this as a serperate project under the same solution
Views Contain your HTML Layouts
Controllers do the heavy lifting of getting data from the models or the models themselves and passing them to the Views.
Models are used to do actions for your BL or fetch data.
Tip : You can use a EntityFramework ( i'm recommending it because it's easy to get started with ) to fetch your data and it's dead simple to setup thus eliminating your DAL and saving you time from writing everything yourself.
Services : you can have controllers that return XML/JSON (other format?) by converting the data you have got from the DB to XML/JSON and returning that instead of a view.
Take a look at MVC 4 WebApi for more details,Note that you can pretty much the same thing with mvc 3 too
Also refer to asp.net/mvc site for tutorials to get you started, they are really useful.
Related
In older web projects that I worked on, we used to create models in DAL, add reference of DAL in Business Logic Layer (and reuse models from DAL as they would be available with reference of DAL), Add reference of BL in Service (again reuse models). Entities were available transitively in all successive layers.
In a MVC project with multiple layers, Models are often added in a separate class library project and referenced across all layers like DAL, Business Logic, Service, FrontEnd etc; Even though they are transitively available.
Is there any specific reason to do this? Why shouldn't we bind Models available through service in frontend like below
#model List<TestSolution.TestServiceRef.Employee>
instead of
#model List<TestSolution.Models.Employee>
What is the advantage of referring models separately in all layers over using it from the reference of another/previous layer?
I don't have a lot of MVC experience (as far as ASP.Net MVC), but as I understand it the Model in MVC is just a representation of the data structures as the coded understands it (i.e. at runtime) - and isn't necessarily the underlying data itself (i.e. database).
If you have a concept that you want to represent in the UI, then obviously the UI needs to know what that concept is - hence referencing it at that level (and other such as the business logic, etc). Pre MVC there was an approach / architecture I followed where the "model" was just a bunch of POCO's (plain old class objects - .e. really simple dumb classes or structs).
These POCO's could go into a an assemply/project like MyApp.Common from where you could safely reference them in any other project / layer of the architecture (UI, Logic, DAL, etc). This allows all layers of the application to "talk the same language", so to speak.
I did a proper write up of this architectural style (which is not MVC, but shares some concepts), here: https://morphological.wordpress.com/2011/08/29/5-layer-architecture/
I am fairly new to ASP.NET MVC. I am really confused about the architecture of my project. Let me explain my confusion to you guys:
In my project I have three parts which are know to all of us. These are: controllers, models and views.
Controllers reside inside Controllers folder, views go inside Views folder and models are inside Models folder.
As we all know there are two types of models: data model and business model. The data model has all the data types to be used in the project and the business models do have additional logic related to the project. In addition to it there is going to be a data layer of the application which talks to the database.
I am going to create a class library project for this data layer which will talk to database. Also, Models folder of my MVC project is going to have data models only and I am going to create a different library for business model classes as well.
Now the problem I am facing is this:
Lets say the name of my MVC project is MVCProj, name of data layer project is DataProj and that of business layer project is BusinessProj.
If I define the data types inside Models folder of MVCProj, I have to include its reference in both BusinessProj and DataProj projects. Also, I then have to use BusinesProj classes in my MVCProj. Thus I have to add reference of BusinessProj in MVCProj which results in circular dependency.
I am not sure if the architecture I am envisioning is correct or not. Please help me sort it out.
Arsen's answer already explained very well, but I just wanted to post my own experiences (and that's too long for a comment.)
Your idea of separating Business logic and DataAcess is good. Most projects I worked on are organized in a similar manner.
What I would do in your case is:
1 - Create a project for DataAcess: MVCProj.DataAcess
2 - Create another project only to contain your database Entities: MVCProj.Entities
3 - Add a reference of MVCProj.Entities in your MVCProj.DataAcessproject
4 - Create a project for your business layer: MVCProj.Business:
5 - Add a reference of MVCProj.Entities and MVCProj.DataAcess in your MVCProj.Business project (I'm assuming business layer will call database)
6 - Add a reference of MVCProj.Entities and MVCProj.Business to your MVC project.
See the logic? Each layer is responsible for doing "its job". Now MVC controllers may call business, wich call the database to save the records. All projects share the same Entities.
The "Models" folder on the MVC project is just an example the team provided. In most examples in the web you see people calling the database (Mainly using Entity Framework) directly inside the controllers. This works, but in the long run is very bad to maintain.
Another thing most people do is: You usually don't want to return your database entities in your controllers. Perhaps they include more properties than you will need and etc. In this case you can create what is called a ViewModel. Think of a ViewModel of something like a copy of your Entity class but only with fields relevant to the View. The ViewModels are specific to the MVC project, so they will stay in a folder inside the MVC project. You may call it Models, or ViewModels, your choice.
Not going much further, but with the separation of projects I showed above you can definetly look for a Dependency Injection framework to handle all the creation of instances of the classes for you. :)
Note: It was implied but all projects except the MVC one are just plain old class libraries.
Hope this helps clarify your ideas.
There is no silver bullet in Architecture, all of this is not a must, but depends from the project...
The amount of layers in your application strongly depends on the requirements.
On the one hand additional layer separate the concerns(example: from DataAccess to Business Logic) on the other hand with each level you increase the amount of work, and decrease performance
Regarding your question, it is ok, when one layer depends to another, it is not ok that the third layer depends on the first one...
In your case you choose 3 level, ideally it should look like this
DataAccess, with its data classes in separate project
BusinessLogic, another project, which call data access, and convert result to its data classes
And finally on the model reference BusinessLogic only
I did a write up that I think my help some of your confusion: Entities are not Models.
TL;DR The main source of your confusion here seems to be that you think you need your "data models" (entities) in the Models folder of your MVC project. That's incorrect on two fronts. First, the Models folder is pretty meaningless. You can rename it, remove it, whatever. It doesn't effect your application at all. Second, and as the post I mentioned details, entities are not models. They are, and should be, merely representations of a table structure to give your ORM (Entity Framework, likely) some place to stuff the data it retrieves from the database.
That said, the typical approach is something like the following:
"DAL" class library containing your context and entities. This is where your migrations will go.
A "business" class library that essentially wraps your DAL and provides basically an API that your MVC project can use to get at the data. Depending on the complexity of your app, this is the layer that's most fungible, as you'll often need to draw a fine line between what is "business logic" that might be universally applicable to any application your organization develops vs. "business logic" that is related to the specific application you're developing.
Your MVC project, which will utilize the DAL/Business layer.
In your MVC project then, your Model folder can basically go away, or you can use it for storing view models, instead. It's common, though, to actually create a ViewModels folder for those specifically. However, it's entirely up to you.
One final note. The "business layer", could also just as well be composed of multiple different class libraries. In my organization, for example, we have a library specifically for working with our POS system, a library for connecting to an API we utilize for email lists, a library for working with Elasticsearch, etc. Our web projects just include whatever libraries they need to utilize.
I'm currently developing business logic in a Controller's ActionResult function, and I've noticed it's becoming unwieldy... large... involves a lot of page ups/downs.
Code includes populating lists for dropdownlists assigned to ViewBag properties, but most of the size is taken up EF (linq to entities) and in memory processing of this.
And finally sent to a view model via Auto Mapper.
Where is the best place to move this code? In another class in the Controllers folder? Or in another class in another folder, i.e. a Business layer?
Separate you project to :
WebUI(View, Controller-A MVC Project)
Business Layer(Holds Business Logic - A class Library Project )
Data Access Layer(Holds Entity Model(May be EDMX) - A class Library Project)
A controller of WebUI project call method of business layer.
If business need data from database then, it will call Data Access Layer.
Funnily enough I answered a very similar question yesterday. In a nutshell, limit your controller to just the minimum logic to link your models with your views. Business logic, data access etc. is better placed in a separate repository.
Bappi Datta is right. Let me just explain it from my point of view.
My best practice with the libs AutoMapper, EF is:
Web - includes logic of rendering, some validation, bootstrap configuration. Calls Business layer methods and classes.
Web.Models - web models with validation attributes
BusinessLogic - business layer. Includes mappings EF Entities <---> Web.Models. Uses Data classes.
Data - Here I always put EF Models and context. Also implementation of Repository pattern could be placed there.
You need to have Repository Layer (which you mentioned you already have) and then you need to have a Service Layer which will hold all your necessary business logic probably using patterns like Command Factory and Facades. Then in order for you to have a flexible and easily pluggable architecture, you need to use Dependency Injection between all layers.
Read about MVC architecture in my perspective
There can be different If's and But's in the theoretical discussion of overall MVC architecture itself. But generally your controller actions needs to be thin, you business logic needs to be in a different layer other than repository.
I'm starting from a point very similar to: Domain Entities, DTO, and View Models.
The advised use of DTOs to map between the domain model and the MVC's ViewModel seems consistent expectations. I seek details of how to bridge the domain model (Entity Framework-based project) to the WebAPI mvc project.
I'm starting with a project of simple POCOs (generated by EF PowerTools to reverse engineer my existent db) that I want to connect to an MVC4 WebAPI project.
I expect I'll be adding business logic to the baseline POCO project as my solution evolves and perhaps this is the crux of this issue. The business logic that transforms the POCOs into something that can be mapped to the MVC project.
Exactly how do I wire these projects together so i can start creating controllers in the MVC project that knows about the entities of the EF project? Automapper? Can we point to posts/docs where this specific feature of Automapper is employed?
You don't want controllers that knows about the EF entities - that's the whole point of this. :)
You yourself say that the DTOs should be used to map your domain to your view model, and then you ask "how can I bridge my domain model with the mvc controllers?". You've already answered this - with DTOs!
The DTO serves as a transport layer between complex business objects and models used to display a certain view. Both of these have special requirements that don't strictly relate to "just data" - hence using DTOs will give you a greater decoupling and separation of concerns.
If you don't decouple domain from view model, you will be forced to directly reference your EF objects in your view model code, which exposes unnecessary data and functions "up the chain".
Now, if you use WebAPI as a way to ship data then I think you could usually get away with sending the DTOs, since WebAPI data usually wouldn't be implementing view model logic. But YMMV of course, depending on how you plan to use your controllers.
For AutoMapper I'd say it's best to start with their own docs (they even use DTO examples in them): http://github.com/AutoMapper/AutoMapper/wiki/Getting-started
In my first ASP.NET MVC applications, the model was a simple O/R mapping between a table and the classes, managed by the Entity Framework.
Now I would like to add some meat to this skeleton, and introduce business methods for the generated classes. What is the recommended approch to this in ASP.NET MVC (with Entity Framework)? My favorite would be solution which also can be used in a service layer, with no ASP.NET MVC references, so that the same domain logic also could be reused in a desktop client.
Technically, I think it should be possible to extend the generated classes in a way which preserves the additional business logic even if the O/R classes need to be refreshed. (This is more a question related to the Entity Framework however.)
Edit: Many thanks for the contributions, and the information about the next version of Entity Framework (4.0). Building two sets of classes, one auto-generated to represent the data in the persistency layer and one for the actual business logic sounds interesting.
Within MVC.Net, the model is the least clearly defined part. In my opinion, it's basically the rest of your application (i.e. anything not related to the View or the Controller). The O/R Mapping part of your application should probably be outside of the "Model" also, as this is more of a data layer. The Model, should really deal in business objects and create views of your data to pass to the View.
There are lots of differing opinions on this, but I think it's best not to think of MVC.Net as traditional MVC Architecture.
If you are using EF v1.0 right now, the Entity Framework is very intrusive into your application, which means that you cannot create POCO very easily. The way you can extend your model is by using the partial class. So when you refresh your model, the partial class you did will still be valid. The Entity Framework team realizes this is a problem , and have improved this in next version (EF V4.0).
NHibernate is much more friendly and allow you easily extend your business logic.
I really think this blog post by Jeremy D. Miller is very good at pointing out the problem.
Abstract your Business Layer out into another project, then pass an instance of it onto your mvc controller using something like structure map. You can then call this Business Layer from your controller to retrieve your business entities (Model) and pass them on to the UI. This will allow you to resuse your Business Layer in your desktop application.
Not only meat but also some clothes and a style could be added to this project to make it seem chic. It depends on the time you have for the project. If you have time, I could suggest you to get a look to TDD and the frameworks that could be used with TDD such as Castle, NUnit, Moq etc.
As you mentioned a service layer is a must for any project but with these kinds of frameworks you could design your architecture more robust.