I am using MVC3 for my application and I have a question about validation. I have a Business Logic layer that is separate from my web layer where I will have a function like CreateUser, which creates a new user for the application to use. I want this function to be accessible in two places: 1) Somewhere in a controller that makes use of it and 2) in a "Setup Data" program that inserts data into the system.
I want to make use of things like ModelState.IsValid to check for all basic validation, but this won't help me for my Setup Data mode (or any other mode that doesn't go through MVC). Is there any way I can still leverage this code, but to contain all validation in my BusinessLogic layer instead of in the controller without having the BusinessLogic layer rely on MVC?
Thanks.
It looks like this article about Service Layers has what I need. Other suggestions are still welcome. Thanks.
Note that the article on service layers still means that you need a dependency on the MVC assembly. After wrestling a bit with this myself recently, I'm now of the opinion that keeping things as separate as possible is a good design. In my model assembly, I have a services folder wherein from, say, a Create() routine, I validate and throw custom exceptions.
The service layer doesn't care who or how these exceptions are consumed. In your MVC app, map them into model state errors collections or whatever. Your design is all the more solid because your model assembly doesn't depend on some validation runner making appropriate use of MVC validation attributes, collections, etc.
I also noticed the article mentions a repository. I know it's all the rage these days but if you're already using an ORM like Entity Framework, a repository is really just a DAO. Reposity is the new Singleton.
Related
I'm trying to learn dependency injection. The book/example I am following seems to be using an MVC project as just the UI layer within a broader architecture. The example includes a separate project for the domain layer and yet another project for the data access layer.
When I first learned MVC I came away thinking MVC was the entire architecture. V for view for UI layer, C for controller for domain layer, and M for model for data access layer.
So is using an MVC project as only the UI layer a proper and/or commonly accepted application of the MVC framework?
So is using an MVC project as only the UI layer a proper and/or commonly accepted application of the MVC framework?
Yes.
While it is possible to make an application entirely within the context of ASP.NET MVC, doing so means that the application will have to be written from scratch to use a different UI framework. Isolating the business logic into a separate set of services that are not coupled to ASP.NET MVC means that only the top layer would need to be replaced to move to a different UI framework, which also means that the application's lifecycle may extend beyond the end of ASP.NET MVC and/or it can be made into an application with a different UI framework (WebApi, WPF, etc) without too much trouble.
The purpose of dependency injection is to decouple your services from all other parts of the application, including each other. So by extension, it is only natural to build the business layer separately from the UI layer. Whether you physically have them in one assembly or multiple is really just a matter of preference.
Applying SRP to the MVC design pattern will lead you there. Same goes for MVVM. You are extracting logic from Model to other classes like Interactors, Services, Repositories etc.
From any point of view this is perfectly normal(and desirable). Your Model is just an abstraction of Several different layers.
I would suggest you to take a look at VIPER (not a car) - https://www.objc.io/issues/13-architecture/viper/ and you will see something that is occuring to you right now.
I have been jumping between articles and questions but i can't seem to find the information i want.
When i started learning about MVC, tutorials and articles pointed out that:
*Models: is where you business logic goes
*Controller: is where data-access and handling request/respond happens.
I have been working with MVC for a while now and I wanted to migrate an old simple project to MVC. In the project i have a business and data access layers.
After reading about N-Tier MVC architecture, my understanding changed.
The model in which i usually presumed to be the business domain has now changed to be more of a presentation depending on views. Its true that models reflects the business entities but it acts as another layer over it.
So my question here is the following: Assume that i have an MVC project and i have another two projects, business and data-access. Is the relation in this manner right ?
*A model, will mostly have the same properties as in its corresponding business entity.
*The controller will call the DataAccess-Layer to retrieve data, the data will be returned as business object which will be mapped into a model and then returned into a view.
Model not always corresponds to business entities. Because models in MVC used to reflect entities that will be sent to view. So they may be little bit sipmlier than domain business entities. It is correct that your domain model will be mapped to mvc model.
Second statement I agree 100%.
Is the relation in this manner right ?
My answer is that depends on your project scale and team size, But let me explain you my projects architecture.
MVC: A presentation layer, It is the startup project of the application.
Common: This is a class library which contains a set of core classes, such as helpers, base classes, ... This project is referenced to all other projects.
Repositories: For reading from and writing to a database, I've created a project and named it repositories. This project is a combination of repository and the Unit of Work pattern. Implementing these patterns can help insulate your application from changes in the data store.
Test: Unit tests are written in this project.
Hope this will help you.
I've started using EF and LINQ in a project and I'm trying to decide on the best approach/pattern to use. Until now I've been using a custom persistence framework that was based on DataSets and XML configuration. Basically it was a VS Custom Tool that would read the XML configuration file and the DataSets and would generate Object Oriented classes with all the necessary properties/associations/methods. This auto-generated classes then were used from the UI and I had the flexibility to expose only what the UI would need.
Now with EF and LINQ, I'm not comfortable with the idea that the UI can use directly the auto-generated classes and all the LINQ stuff. It seems that this approach would have a very tight integration between UI and the database.
So I'm looking for some pattern that would "hide" all the EF and LINQ goodies and basically limit what the UI can do. Is there any standard way to do this?
What you're looking for is an n-tier application. It's not so much a pattern as an architecture. You break your app up into 2 or more pieces, typically 3 composed of UI, business and Data. You might implement this through other patterns such as the Facade or Repository patterns to keep a strong seperation of concerns.
You might also use a Service Layer, which could be implemented by a facade or as a web service.
You would, ideally, pass data through objects called DTO's or Data Transfer Objects, and you might adapt those DTO's by using a view model in your UI (not to be confused with MVVM which another poster erroneously mentioned.)
Beyond that, much of it depends on the type of app you're buiding. Desktop app, server app, web app, etc..
The pattern you're looking for is, in general, Model-View-ViewModel, or MVVM.
Here's a tutorial that seems to hit on the high points of the design pattern: http://csharperimage.jeremylikness.com/2010/04/model-view-viewmodel-mvvm-explained.html
I've been using ASP.net MVC for about two years now and I'm still learning the best way to structure an application.
I wanted to throw out these ideas that I've gathered and see if they are "acceptable" ways in the community to design MVC applications.
Here is my basic layout:
DataAccess Project - Contains all repository classes, LINQ-to-SQL data contexts, Filters, and custom business objects for non-MS SQL db repositories (that LINQ-to-SQL doesn't create). The repositories typically only have basic CRUD for the object they're managing.
Service Project - Contains service classes that perform business logic. They take orders from the Controllers and tell the repositories what to do.
UI Project - Contains view models and some wrappers around things like the ConfigurationManager (for unit testing).
Main MVC Project - Contains controllers and views, along with javascript and css.
Does this seem like a good way to structure ASP.NET MVC 2 applications? Any other ideas or suggestions?
Are view models used for all output to views and input from views?
I'm leaning down the path of making view models for each business object that needs to display data in the view and making them basic classes with a bunch of properties that are all strings. This makes dealing with the views pretty easy. The service layer then needs to manage mapping properties from the view model to the business object. This is a source of some of my confusion because most of the examples I've seen on MVC/MVC2 do not use a view model unless you need something like a combo box.
If you use MVC 2's new model validation, would you then validate the viewmodel object and not have to worry about putting the validation attributes on the business objects?
How do you unit test this type of validation or should I not unit test that validation messages are returned?
Thanks!
Interesting.
One thing I do differently is that I split off my DataAccess project from my Domain project. The domain project still contains all the interfaces for my repositories but my DataAccess project contains all the concrete implementations of them.
You don't want stuff like DataContext leaking into your domain project. Following the onion architecture your domain shouldn't have any dependencies on external infrastructure... I would consider DataAccess to have that because it's directly tied to a database.
Splitting them off means that my domain doesn't have a dependency on any ORM or database, so I can swap them out easily if need be.
Cheers,
Charles
Ps. What does your project dependency look like? I've been wondering where to put my ViewModels. Maybe a separate UI project is a good idea, but I'm not entirely sure how that would work. How do they flow through the different project tiers of your application?
I know that an MVC framework allows you to separate business logic, data base access and presentation, but why do we need a framework to do this.
Can't we just keep our classes separated, perhaps using different packages/folders for the model, view and controller classes?
In my opinion the thing you are talking about is the MVC pattern and not a specific framework. Of course you can go and keep all your classes within one project and still use the MVC pattern, as you have all your UI code in the views, the logic in the controllers, ...
A MVC framework on the other hand makes it easier for you to use this pattern. It may provide some base classes for controllers and a mechanism for the communication between view and controller.
I don't know if you are familiar with ASP.NET MVC. The framework itself is very small, but it helps you developing an application with the MVC pattern, as you don't have do think about the previously decribed areas...
Hope this helps
An MVC framework is a framework written to split up the the business logic, database access and presentation.
This is very useful in most web applications, and now lately into software/desktop applications.
This is due to the fact that following the MVC model, your code will be much clearer, cleaner and you keep your application DRY (Do not Repeat Yourself).
You can write your own classes and separate them into Model, View and Control. But again, you will need a framework to help you in accomplishing certain tasks. Like a List control in ASP.NET, or PHP framework being able to help you translate text between languages and so on. (Oh why reinvent the wheel?!)
MVC and framework is a different thing. MVC is just an architectural pattern, which can be applied with any project, with or without framework.
So you don't need a framework to do this. You can separate them by yourself. :)
MVC stands for “MODEL” “VIEW” “CONTROLLER”. ASP.NET MVC is an architecture to develop ASP.NET web applications in a different manner than the traditional ASP.NET web development. Web applications developed with ASP.NET MVC are even more SEO (Search Engine) friendly.
Developing ASP.NET MVC application requires Microsoft .NET Framework 3.5 or higher.
Model:
MVC model is basically a C# or VB.NET class.
A model is accessible by both controller and view.
A model can be used to
pass data from Controller to view.
A view can use model to display
data in page.
View:
View is an ASPX page without having a code behind file.
All page specific HTML generation and formatting can be done inside view.
One can use Inline code (server tags ) to develop dynamic pages.
A request to view (ASPX page) can be made only from a controller’s action method
Controller:
Controller is basically a C# or VB.NET class which inherits system.mvc.controller.
Controller is a heart of the entire MVC architecture.
Inside Controller’s class action methods can be implemented which are responsible for responding to browser OR calling views.
Controller can access and use model class to pass data to views
Controller uses ViewData to pass any data to view.
MVC is a code organization architecture style to organize your code-logic in a meaningful way for web applications. As a programmer I have almost puked when I have inherited other people's code when their code logic is all over the place and following their web application code turns into following a rabbit down the gutter hole. Why MVC? hmm.. well why should I use a filing cabinet or folders to organize my plethora of paper and not just have my papers stashed in a large pile and have others figure how they connect to each other. It increases code readability. With MVC it becomes very easy to follow code logic since you are following standard structure for a web application. Business logic is separated out from UI. Easier to delegate work decouple work on a project.
You can of course approach it yourself by segregating your classes. A framework supplies common scaffolding that you wouldn't have to build yourself. But it will also impose some structure on your code. You'll have to evaluate whether the framework helps more than it hurts.
You are correct, there are strategies that you can implement to help with separation of concerns without using MVC.
Microsoft's ASP.NET MVC framework is one strategy that can be employed, and that is what I think you are asking about.
This MVC framework makes such separation of concerns easy.
The other major advantage of MVC is testability - (depends on whether you believe in unit testing - I do).
The MVC framework ensures that all orchestration logic is on your controllers and through the FormControls collection allows full unit testing of all aspects of your application except for how it is presented.
As the MS MVC framework encourages adherence to common rules and structure of the application which should lead to greater maintainability.
The major downside of MVC is the code-in-front code weaving required for presentation, but this can be easily overcome.
Perhaps this is just a linguistic thing. I've seen "frameworks" referring to themselves as a DSL -- Domain Specific Language.
And you don't need a framework But here's something to consider: You already know for a web app you're going to want to do a few common things... route URLs, render pages, etc. Why re-write it all? For other problem domains you'll have generic things to do as well.
Hai Friends There are somemany types of architecture frame work has been there,firstly i know 2tier and 3 tier frame work ,the 3 tier and mvc ,entity framework are same but in different name's,so study a good background in any one architecture there fore if you went to any multinational companies ,you can easly score/highlight to your carrer.
Model View Controller or MVC as it is popularly called, is a software design
pattern for developing web applications. A Model View Controller pattern is made
up of the following three parts:
**Model** - The lowest level of the pattern which is responsible for maintaining data.
**View** - This is responsible for displaying all or a portion of the data to the user.
**Controller** - Software Code that controls the interactions between the Model and View