I am using Web->Service->Data layer architecture and in order to do some logging with log4net I would need to install to all these three projects. Also I want to decouple the concrete logger in case I would want to change it later in the process. I am using Autofac IOC for injection. Is there a way to add log4net package once and use it between the layers? I found some blog posts about this but there was not much code so I could not get a good grasp on it, you can either give some directions or an explanation of how to achieve this.
Thanks for your time
There's a really small assembly which only contains a logging interface, no implementation, that you can use to decouple your assemblies from your logging implementation. It's called "Common Logging" and is available in NuGet.
You add a reference to Common.Logging in all your projects that need logging, and then through XML configuration or in your bootstrap code you can inject a concrete logging implementation, such as Log4Net. It also supports other logging frameworks.
Related
i've been trying to get my head around on EntLib 5.1 Unity and it's confusing me a lot http://msdn.microsoft.com/en-us/library/ff660864%28v=PandP.20%29.aspx.
Could anyone please tell me on what type of scenario I can use Unity?
I've a requirement to load the specific dll based on request type. Can Unity be used on this scenario?
Thanks a lot.
For dynamically loading DLLs, you may want to take a look at MEF.
Unity is for decoupling dependencies among classes to make it easier to write testable, reusable code.
It is an Inversion of Control (IoC) container library that makes it easier to do Dependency Injection. There are numerous examples on Stack Overflow. Note that you can configure Unity in code (my preference) or with a configuration file.
I'm starting a new personal Prism 4 project. The Reference Implementation currently uses Unity.
I'd like to know if I should use MEF instead, or just keep to Unity.
I know a few discussions have mentioned that these two are different, and they do overlap, but will I be missing out if I simply choose Unity all the way?
Also check out the documentation:
Key Decision: Choosing a Dependency Injection Container
The Prism Library provides two options
for dependency injection containers:
Unity or MEF. Prism is extensible,
thereby allowing other containers to
be used instead with a little bit of
work. Both Unity and MEF provide the
same basic functionality for
dependency injection, even though they
work very differently.
Some of the capabilities provided by both containers include the following:
They both register types with the container.
They both register instances with the container.
They both imperatively create instances of registered types.
They both inject instances of registered types into constructors.
They both inject instances of registered types into properties.
They both have declarative attributes for marking types and dependencies that need to be managed.
They both resolve dependencies in an object graph.
Unity provides several
capabilities that MEF does not:
It resolves concrete types without registration.
It resolves open generics.
It uses interception to capture calls to objects and add additional functionality to the target object.
MEF provides several
capabilities that Unity does not:
It discovers assemblies in a directory.
It uses XAP file download and assembly discovery.
It recomposes properties and collections as new types are discovered.
It automatically exports derived types.
It is deployed with the .NET Framework.
I am currently doing the same investigation. I was last week attending the p&p symposium at Redmond. I had the chance to chat with some of the p&p people on that.
MEF
+Part of .net, no need for extra libraries
+Very powerful in extensibility, modularity scenarios
-More generic approach, less flexible for DI scenarios
-You need to decorate with attributes, your code is glued to MEF
Unity
+Very flexible for DI scenarios
+If you stick with ctor injection and avoid using named instances then you
don't need to use any attributes. Most
of your system doesn't rely on Unity
-No out of the box support for extensibility, modularity scenarios
-Need to deploy the 3rdparty libraries
What I think is a good idea is to use MEF for extensibility (manage the modules of your app, localize registrations) and use Unity for DI.
Well this has to be clear that MEF implements Inversion of control but it is not a part of it, so this means that they are not same, there is a difference, that we use unity when we have static dependency and MEF provides us with dynamic dependency.
MEF also provides us with extensibility, by which we can induce a port type mechanism and can also specigy the type of component which can interact via that port.
more can be understood from: MSDN Document
I'm working on an ASP.Net website along with a supporting Class Library for my Business Logic, Data Access code, etc.
I'm EXTREMELY new and unfamiliar with the Unity Framework and Dependency Injection as a whole. However, I've managed to get it working by following the source code for the ASP.NET 3.5 Portal Starter Kit on codeplex. But herein lies the problem:
The Class Library is setup with Unity and several of my classes have [Dependency] attributes on their properties (I'm exclusively using property setter injections for this). However, the Global.asax is telling Unity how to handle the injections....in the Class Library.
Is this best practice or should the Class Library be handle it's own injections so that I can re-use the library with other websites, webapps or applications? If that is indeed the case, where would the injection code go in this instance?
I'm not sure how clear the question is. Please let me know if I need to explain more.
Though not familiar with Unity (StructureMap user) The final mappings should live in the consuming application. You can have the dll you are using define those mappings, but you also want to be able to override them when needed. Like say you need an instance of IFoo, and you have one mapped in your Class Library, but you've added a new one to use that just lives in the website. Having the mappings defined in the site allows you to keep things loosely coupled, or else why are you using a DI container?
Personally I try and code things to facilitate an IOC container but never will try and force an IOC container into a project.
My solution breakdown goes roughly:
(Each one of these are projects).
Project.Domain
Project.Persistence.Implementation
Project.Services.Implementation
Project.DIInjectionRegistration
Project.ASPNetMVCFrontEnd (I use MVC, but it doesn't matter).
I try to maintain strict boundaries about projects references. The actual frontend project cannot contain any *.Implementation projects directly. (The *.implementation projects contain the actual implementations of the interfaces in domain in this case). So the ASPNetMVCFrontEnd has references to the Domain and the DIInjectionWhatever and to my DI container.
In the Project.DIInjectionWhatever I tie all the pieces together. So this project has all the references to the implementations and to the DI framework. It contains the code that does the registering of components. Autofac lets me breakdown component registration easily, so that's why I took this approach.
In the example here I don't have any references to the container in my implementation projects. There's nothing wrong with it, and if your implementation requires it, then go ahead.
I want to isolate all my code from the IoC container library that I have chosen (Unity). To do so, I created an IContainer interface that exposes Register() and Resolve(). I created a class called UnityContainerAdapter that implements IContainer and that wraps the real container. So only the assembly where UnityContainerAdapter is defined knows about the Unity library.
I have a leak in my isolation thought. Unity searches for attributes on a type's members to know where to inject the dependencies. Most IoC libraries I have seen also support that. The problem I have is that I want to use that feature but I don’t want my classes to have a dependency on the Unity specific attribute.
Do you have any suggestions on how to resolve this issue?
Ideally I would create my own [Dependency] attribute and use that one in my code. But I would need to tell the real container the search for my attribute instead of its own.
Check out the Common Service Locator project:
The Common Service Locator library
contains a shared interface for
service location which application and
framework developers can reference.
The library provides an abstraction
over IoC containers and service
locators. Using the library allows an
application to indirectly access the
capabilities without relying on hard
references. The hope is that using
this library, third-party applications
and frameworks can begin to leverage
IoC/Service Location without tying
themselves down to a specific
implementation.
Edit: This doesn't appear to solve your desire to use attribute-based declaration of dependency injection. You can either choose not to use it, or find a way to abstract the attributes to multiple injection libraries (like you mentioned).
That is the basic problem with declarative interfaces -- they are tied to a particular implementation.
Personally, I stick to constructor injection so I don't run into this issue.
I found the answer: Unity uses an extension to configure what they call "selector policies". To replace the attributes used by Unity, you just code your own version of the UnityDefaultStrategiesExtension class and register you own "selector policies" that use your own attributes.
See this post on the Unity codeplex site for details on how to do that.
I'm not sure that it's going to be easy to do the same if I switch to another IoC library but that solves my problem for now.
Couldn´t you just setup your configuration without the attributes, in xml. That makes it a bit more "unclear" I know, personally I use a combination of xml and attributes, but at least it "solves" your dependency on unity thing.
I have been building web sites with ASP.NET for a while now. At first I avoided learning the intricacies of the ASP.NET Provider Model. Instead I used the canned providers where necessary, and leaned heavily on Dependency Injection frameworks for all my other needs.
Recently however, I have been writing pluggable components for ASP.NET and of course writing lots of custom provider based solutions in order to make that happen. It has become quickly apparent to me however, that a lot of initialization code is being duplicated, which is a bad thing.
So...
Are there any best practices that have emerged on how to avoid the configuration spaghetti code?
Have you built, or have any examples (base/helper classes, custom attributes, reflection) to share of abstracting the basic initialization code out so building custom providers is easier?
NOTE:
Please do not try and send me to the Provider Toolkit site. I have already exhausted that resource, which is why I am turning to the SO Community :)
I just did a rough implementation of rather basic implementation of the membership and role providers, and I don't have any code duplication at all!
I have divided everything into three projects (plus tests):
Application - asp.net mvc app. models, controllers etc.
Infrastructure - IoC and Interfaces
Infrastructure.Web - Providers
The model for User and Role implement interfaces from Infrastructure and those classes get registered to the IoC on application startup. The providers then asks the IoC to resolve the classes and does it's thing. This way I can add things to the model and user interface yet using the same providers. The one problem I've noticed, is that the web being launched by the "ASP.NET Configuration"-button can't use the providers, as the setup is being done in Application_Start and the "ASP.NET Configuration" is another web. I don't see this as a problem though.