Dependency Injection And Code Maintainability?
Oct 30, 2010
I am working on a (vb.net/asp.net) project that is using interfaces to provide dependency injection. But to me, it feels like the maintainability of the code has been killed. When I want to read through the code, I can't simply jump to the code of a related class that is used. All I see are the interfaces, and so I have to hunt through the project to figure out what classes are doing the implementation. This really hurts my productivity.
Yes, I know I now can implement the interfaces with a wide variety of replacement classes. But for example, I know I'm not changing my data source any time soon--there is no need for me to enable the ability to swap that out. All of this dependency injection seems like overkill to me (in fact, the only real reason it is there is to support mock classes for unit testing). I've actually read several places that state DI is actually better for maintainability. But that assumes you already know where everything is and you know which class you need to update. Finding out where to look is the part that is killing me. So, my question is: Is there a better way to traverse through the code? Is there a better way to make the code more maintainable? Are we just doing it wrong? Or is this par for the course?
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Jul 20, 2010
I have a page using an injected BLL service: a simple service returning a set of objects with a function like this:
public IMyService { List<Foo> All(); }
There is a default implementation for normal users.Now, i need that users in administrative role can view more objects, with another implementation of the service.Where can i configure my page to use the second implementation?
My first solution is to put the dependency to the IUnityContainer in the page, and use it to resolve the dependency:
[Dependency]
public IUnityContainer Container { get; set;}
Page_Init(..) [code].....
it's a ServiceLocator and it's neither scalable neither testable.
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Jan 3, 2011
During the design of a new generic authentication framework for some of our products, I have come across an architectural issue I cannot seem to find a good solution for.I have tried to simplify the problem in order to easily explain it.
The library has two classes:
Manager Is responsible for storing currently authenticated users.Module It is the responsibility for the module to validate each request according to security policies. The Module must ask the manager to determine whether a user is currently authenticated.
Now the manager is supplied an implementation of an interface which allows the manager to load users from a repository. The specific implementation is not contained in this library. Because of this, I cannot directly instantiate an instance of the repository within the library.
I have no way of modifying properties or supplying arguments for the module constructor. So my question is this, how can I give the module a reference to an instance of the Manager?
namespace Demo
{
public interface IRepository
{[code].....
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Apr 2, 2010
as i've read Ninject is the best one so how to use it and why i cannot see good examples.
Lately i have begun learning MVC and as i've seen every one use DI in the MVC, i have a couple doesn question but i will ask a few lol...
1. Why use and what is going to do for me?
2. How to use it in WebForms Appliction ?
3. IoC is the same if not what is it and what's it doing?
4. I want to use a Ninject FrameWork 2.0 but i cannot find good examples for WebForm App.
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Jul 20, 2010
I have a custom constraint that queries a value against a repository. Is it possible to replicate the dependency injection available to controller constructors?
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Jan 25, 2011
This project is pretty far away and I'm not in the position to go make changes all over the place (If I could, deleting the lot would be what I'd do!)
I want to create a modelbinder that would resolve any dependencies my View Models might have (using StructureMap).
It should not require me to implement a specific interface (so many developers, so many interfaces..I rather keep things clean) and hopefully not require one to go register each model binder individually (Now I'm asking too much,taking the first requirment
in consideration).
Probably will get it right tonight, but figured I'd ask.
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Apr 8, 2010
Recently I was asked to express the DI in colloquial explanation.
I answered :
1)I am going to a hotel.I ordered food.The hotel management asks me to clean the plates and
clean the tables.So here i am a client,I am responsible for managing the service (Instantiating,executing,disposing).But DI decouples such tasks so the service consumer no need not worry about controlling the life cycle of the service.
2)He also asked is there any microsoft API follows DI ?.I answered (This was my guess) In WCF you can create a Proxy using ChannelFactory that controls the life time of your factory.
for item (1) he said only 10% is correct
for item(2) he said that is factory pattern not dependency injection.
Actually what went wrong in my explanation (apart from my bad English) ? What is the real answers for those?
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Nov 27, 2010
I have been looking at learning dependency injections (i think i have now grasped the basics) and am looking to implement it into a webform application. My question is, what dependency injection framework should i use for a webforms project, or is it a question of what works best for you?
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Most of the information i come across relates to dependency injection whilst in a MVC environment. And have also read that some frameworks such as Structure Map only work with webforms using version 2.0 or earlier. So the kind of things i need to consider are whether webforms will be continuous support, and the ease of configuration for someone relatively new to the pattern.
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Aug 12, 2010
I am sure that I am somewhat lost in this area... my understanding is that Dependency Injection means initializing something that is required by a class..so for instance. If my controller is going to need a service and I want to be able to test it then I should define two Constructor methods for it... so, my question is.
public class CompaniesController : Controller
{
private ICompaniesService _service;
public CompaniesController()
{.......
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May 27, 2010
My general understanding of the MVC pattern is that the model is reponsible for persisting itself. Though I also see other opionions that models should be dumb data objects and that controllers should persist them via a data access layer.
Per http://en.wikipedia.org/wiki/Model_view_controller: "Many applications use a persistent storage mechanism such as a database to store data. MVC does not specifically mention the data access layer because it is understood to be underneath or encapsulated by the model." Though it does also mention "Models are not data access objects."
Per http://www.asp.net/mvc/tutorials/asp-net-mvc-overview--cs, "Models. Model objects are the parts of the application that implement the logic for the applications data domain. Often, model objects retrieve and store model state in a database. For example, a Product object might retrieve information from a database, operate on it, and then write updated information back to a Products table in SQL Server."
First, am I misguided in believing that models should persist themselves? Or, is this just a matter of opinion?
Second, if I follow the pattern where controllers manage the persistence of the model, I find it fairly easy to use dependency injection to inject a data access component into my controller using a custom controller factory (implementing the IControllerFactory
interface). If I follow the pattern where my model saves itself, I'd want to inject my data access component into the model. Is there a way to provide a custom factory for models? Otherwise, I don't think using DI with models is possible.
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Nov 11, 2010
private IGetData _getData;
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Jul 21, 2010
i'm just starting with asp.net mvc and specifically the repository pattern. I've read as much as i can but there doesn't appear to be a great article on dependency injection (ioc) as lots of people are doing it different. I found one article
http://weblogs.asp.net/cibrax/archive/2008/08/21/dependency-injection-made-easy-for-the-asp-net-mvc.aspx and it looks simple for setting up my data context (IDataContext) against a controller. However i have my own custom DataAnnotation attribute which
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{
public override bool IsValid(object value)
{
string str = (string)value;
if (string.IsNullOrEmpty(str))
return true;
using (IDataContext context = new LinqToSqlDataContext())
{
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}
}
}
As you can see there's a hard coded dependency on my linq to sql data context. This means i can't test but i also can't see what else i can do.I'd really appreciate it if someone could point me in the right direction and recommend the best dependency injection library to use (such as StructureMap, Unity, Autofac...).
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Dec 17, 2010
I've created a base page type that derives from WebViewPage<T>.
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Whilst this works fine on a normal view page, my services are not injected on a Layout page.
Are the base types for a standard view page and layout page the same?
If I call IDependencyResolver directly in the base page type then it works fine but I would prefer not to do this.
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Feb 21, 2011
I am sort of new to Entities Framework however I have successfully built a complete CMS website with the Entities Framework 4.0 in MVC 2.0 following the design patterns and examples laid out in nerddinner and MusicStore.
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I know I might sound silly to some however I need a few pointers on creating this ASP.NET web application to use Entity Framework and use something like the design pattern of Dependency Injection etc... and still able to bind to GridViews programmatically in code behind.
I like the seperation of using a ntiers design but also would like to have full code control and not be forced to use ObjectDataSources in my aspx page.
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Aug 16, 2010
Does anyone have a list of link(s) on the www for a good list of DI gotchas?I have been trying to inject controls using DI, in an asp.net webforms app and found that on recursive build up that ViewState is lost.
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Jan 6, 2011
Here's what I want to do:
UI layer: An ASP.NET webforms website.
BLL: Business logic layer which calls the repositories on DAL.
DAL: .EDMX file (Entity Model) and ObjectContext with Repository classes which abstract the CRUD operations for each entity.
Entities: The POCO Entities. Persistence Ignorant. Generated by Microsoft's ADO.Net POCO Entity Generator.
I'd like to create an obejctcontext per HttpContext in my repositories to prevent performance/thread [un]safety issues.
public MyDBEntities ctx
{
get
{
string ocKey = "ctx_" + HttpContext.Current.GetHashCode().ToString("x");
if (!HttpContext.Current.Items.Contains(ocKey))
HttpContext.Current.Items.Add(ocKey, new MyDBEntities ());
return HttpContext.Current.Items[ocKey] as MyDBEntities ;
}
}
I don't want to access HttpContext in my DAL (Where the repositories are located). But I have to somehow pass HttpContext to DAL. based on the answer to my question here, I have to use IoC pattern.
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May 2, 2010
I have an ASP.NET MVC web application that implements a custom membership provider. The custom membership provider takes a UserRepository to its constructor that provides an interface between the membership provider and NHibernate. The UserRepository is provided by the Ninject IoC container.
Obviously, however, this doesn't work when the provider is instantiated by .NET: the parameterless constructor does not have a UserRepository and cannot create one (the UserRepository requires an NHibernate session be passed to its constructor), which then means that the provider cannot access its data store. How can I resolve my object dependency?
It's probably worth noting that this is an existing application that has been retrofitted with Ninject. Previously I used parameterless constructors that were able to create their required dependencies in conjunction with the parametered constructors to assist unit testing.
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May 12, 2010
I've just started wokring with Asp.Net mvc and i relay love it. One thing I don't know how to do it yet is:
If I want to develope a new user control (e. g. PeoplePicker) how I get the data? I don't want to use allways ajax requests, some controls should be initialized when the page is loaded. So I could use the Html Helpers and create own extension. So far this is exactly what i want and it's working. But now to the real problem. I can't use dependency injection in extension methods (I'm using spring.net, but the problem should be in all di frameworks).
So which approche is the most common to use this problem? Must I realy pass in the data from my controller? But then the controller must know how my user controls works, I don't want that!
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Mar 8, 2010
Im faced with an impending upgrade to an ASP.NET site and I am thinking of introducing DI using Unity. I have researched the ASP.NET DI side of things and have 2 options (Global.asax or IHttpModule). Im happy to use either. As always, there is a legacy object model in place that I would like to upgrade/change. I would like to go down the route of Constructor injection (passing in the DAO) however, each object has a mix of static and instance methods that both currently call into the DB using SqlCommand objects themselves. I want this removed to provide DB independence, therefore can anyone suggest the best way to do the DI in this case? Im open to drastic changes if they are needed.
public class ExampleClass
{
public ExampleClass(int test)
{
TestProperty = test;
}
public int TestProperty {get; set;}
public int Save()
{
// Call DB and Save
[Code]....
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Aug 6, 2010
I will like to add Rhino Service Bus to my ASP.NET web application but using Ninject as the DI Container. So far all examples I keep seeing use Castle Windsor which I don't want to use since we already use Ninject.Are there any tutorials out there which show how to add Rhino Service Bus to an ASP.NET web application without a direct dependency on Castle Windsor (e.g. using Ninject)?
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Sep 7, 2010
I have a [BeastAuthenticate] attribute on my controller. The following code works fine but I would like to use Contructor (Dependency) Injection with Unity. The problem is that the attribute will run the contructor with no parameters. terfaces ITMSLogger and IADGroups are setup to use Dependency Injection with TMSLogger and ADGroups respectively. The following code works fine but doesn't use dependency injection for class ADGroups.
[Code]....
I tried the following but I'm getting an error ("Object reference is required...") with "this (adGroups).
[Code]....
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Dec 14, 2012
I have a class User as ahown bellow.
Public class User {
public string userName { get; set ; }
public string userId { get; set; }
}
Once user logins i am populating userName, userId
And storing user class object in to session.
session["User"] = objUser
I have another Class Consumer as shown Bellow.
Public Class Consumer {
//constructors
public Consumer(User user) {
// some code goes Here.
}
}
I am Using spring frame work To initialize the class using dependency injection.
So my question is how can i pass stored user session to constructor using springs.
same config is given below.
<object id="objConsumer" type ="Namesapce.consumer, consumer"> <constructor-arg Value="User"/> </object>
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Jul 23, 2010
how to complete my implementation of the Repository pattern in an ASP.NET web application.
At the moment, I have a repository interface per domain class defining methods for e.g. loading and saving instances of that class.
Each repository interface is implemented by a class which does the NHibernate stuff. Castle Windsor sorts out the DI of the class into the interface according to web.config. An example of an implemented class is provided below:
[code].....
As pointed out in a previous thread, the repository class needs to accept an unit of work container (i.e. ISession) rather than instantiating it in every method.
I anticipate that the unit of work container will be created by each aspx page when needed (for example, in a property).
How do I then specify that this unit of work container instance is to be passed into the constructor of StoredWillRepository when Windsor is creating it for me?
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Jun 2, 2010
How can i restrict sql injection in my code. How can i test that one whether SQL injections are applicable or not
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Jan 18, 2011
I'm working on a C# web app and I've to handle some javascript code.
I can do it both using javascript injection from my .cs file, which I'm doing now or choose to include my code into an external js file.
I would like to know when you would prefer to choose one way over the other.
According to me, it can be more clear to put code in external .js file and it can ease debugging.
Code injection from code-behind would however keep together all the necessary code for my component.
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