I am developing an ASP.NET MVC app and I've been looking into using Data Annotations on my POCO's which are defined in my Service Layer. As long as I have a reference to System.ComponentModel & System.ComponentModel.DataAnnotations this is no problem and what I like about this is that it allows me to reuse my Service Layer in a Win Forms app.
I'm now looking to do some Remote Validation using Data Annotations and have taken a look at this article: http://msdn.microsoft.com/en-us/library/ff398048(VS.100).aspx
However, to use the Data Annotations in this context I need to reference System.Web.MVC,
System.Web and System.Web.Routing. This introduces a dependency on the Web DLL's, which
limits me somewhat.
Can anyone recommend a good clean way to implement Remote Data Validation using Data Annotations that isn't coupled with ASP.NET MVC or maybe suggest a better alternative.
Thanks for the help !
I resolved this in the end by backing away from putting DataAnnotations on my POCO's and instead I put them on my ViewModels and use AutoMapper to Map between my ViewModel and POCO (which saves me some time doing tedious mapping). There's a great video on Automapper here http://perseus.franklins.net/dnrtvplayer/player.aspx?ShowNum=0155
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Folks,
I am brand new to asp.net web APIs and need your help, I am using mvc4 Empty webapi project, I have a single controller called recordsController.
I have data that I need to persist in memory, and would like to use dependency injection to access this data model in my controller when a request arrives.
Is there any built in dependency injection that I can use ? if not, what is the best quick and dirty to accomplish this ?
Thanks in advance
DO you want DI or data persistence, they are not the same thing at all.
If you want to use shared memory between all requests without using some kind of backend (Database,file and so on) then check MemoryCache -> https://msdn.microsoft.com/en-us/library/system.runtime.caching.memorycache(v=vs.110).aspx
DI is used for runtime type resolution and has nothing to do with data persistence.
https://en.wikipedia.org/wiki/Dependency_injection
I will start to code a new Web application soon. The application will be built using ASP.Net MVC 3 and Entity Framework 4.1 (Database First approach). Instead of using the default EntityObject classes, I will create POCO classes using the ADO.NET POCO Entity Generator.
When I create POCOs using this tool, it automatically adds the Virtual keyword to all properties for change tracking and navigation properties for lazy loading.
I have however read and seen from demonstrations, that Julie Lerman (EF Guru!) seems to turn off lazy loading and also modifies her POCO template so that the Virtual keyword is removed from her POCO classes. Julie states the reason why she does this is because she is writing applications for WCF services and using the Virtual keyword with this causes a Serialization issue. She says, as an object is getting serialized, the serializer is touching the navigation properties which then triggers lazy loading, and before you know it you are pulling the whole database across the wire.
I think Julie was perhaps exagarating when she said this could pull the whole database across the wire, however, even so, this thought scares me!
My question is (finally), should I also remove the Virtual keyword from my POCO classes for my MVC application and use DectectChanges for my change tracking and Eager Loading to request navigation properties.
Your help with this would be greatly appreciated.
Thanks as ever.
Serialization can indeed trigger lazy loading because the getter of the navigation property doesn't have a way to detect if the caller is the serializer or user code.
This is not the only issue: whether you have virtual navigation properties or all properties as virtual EF will create a proxy type at runtime for your entities, therefore entity instances the serializer will have to deal with at runtime will typically be of a type different from the one you defined.
Julie's recommendations are the simplest and most reasonable way to deal with the issues, but if you still want to work with the capabilities of proxies most of the time and only sometimes serialize them with WCF, there are other workarounds available:
You can use a DataContractResolver to map the proxy types to be serialized as the original types
You can also turn off lazy loading only when you are about to serialize a graph
More details are contained in this blog post: http://blogs.msdn.com/b/adonet/archive/2010/01/05/poco-proxies-part-2-serializing-poco-proxies.aspx
Besides this, my recommendation would be that you use the DbContext template and not the POCO template. DbContext is the new API we released as part of EF 4.1 with the goal of providing greater productivity. It has several advantages like the fact that it will automatically perform DetectChanges so that you won't need in general to care about calling the method yourself. Also the POCO entities we generate for DbContext are simpler than the ones that we generate with the POCO templates. You should be able to find lots of MVC exampels using DbContext.
Well it depends on your need, if you are going to serialize your POCO classes than yes you should remove them (For example: when using WCF services or basically anything that will serialize your entire object). But if you are just building a web app that needs to access your classes than I would leave them in your classes as you control the objects that you will access in your classes through your code.
I have an MVC3 project with a requirement to use LDAP to fill in several personnel properties on one of my Model classes. I have done this before in .Net 3.5 but wasn't sure how to approach it in MVC3. Would I take the same approach or is there an HTML helper or some other mechanism in MVC3 that I could/should use?
Keep doing what you have been doing. When building your ViewModel (preferably in a repository layer), you can use LDAP as your data source for the necessary properties.
You do not want to do this in a view, as the view should not have any logic other than presentation logic.
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.
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?