Which Dependency Injection Tool Should I Use?

Question

I am thinking about using Microsoft Unity for my Dependency Injection tool in our User Interface.

Our Middle Tier already uses Castle Windsor, but I am thinking I should stick with Microsoft.

Does anyone have any thoughts about what the best Dependency Injection tool is?

• Autofac
• Castle MicroKernel/Windsor
• PicoContainer.NET
• Puzzle.NFactory
• Spring.NET
• StructureMap
• Ninject
• Unity
• Simple Injector
• NauckIT.MicroKernel
• WINTER4NET
• ObjectBuilder

Answer 1

Having recently spiked the use of 6 of these (Windsor, Unity, Spring.Net, Autofac, Ninject, StructureMap) I can offer a quick summary of each, our selection criteria and our final choice.

Note: we did not look at PicoContainer.Net as one of our team considered the .Net port to be quite poor from the Java version. We also did not look at ObjectBuilder, as Unity is built on top of ObjectBuilder2 and was considered to be a superior choice by default.

Firstly, I can say that more or less all of them are all pretty similar and it really comes down to what really works best for you, and your specific requirements. Our requirements included:

Requirements

• Constructor based injection (we intend not to use property, field or method injection)
• Programmable configuration (not XML)
• container hierarchies (one per application, per request and per session to more implicitly bind component lifetimes scope to container)
• component lifetime management (for more granular scoping eg transient / singleton)
• injection from interface to type or concrete instance (eg ILogger -> typeof(FileLogger) or ILogger -> new FileLogger() )
• advanced component creation / "creaton event mechanism" for pre/post initialisation
• correct disposal of IDisposable components on container tear down

• well documented and/or online information readily available

  Note: whilst performance was a requirement it was not factored in the selection as it seemed that all containers reviewed were similar according to this benchmark

Test

Each container was used in a typical Asp.Net webforms project (as this was our target application type). We used a single simple page with with a single simple user control, each inheriting from a base page / base control respectively. We used 1 container on the BasePage for a "per request" scope container and 1 on the global.asax for an "application" scope and attempted to chain them together so dependencies could be resolved from both containers.

Each web application shared a contrived set of domain objects simulating multi-levels of dependency, scope type (singleton/transient) and also of managed and unmanaged classes (IDisposable required). The "top level" dependency components were manually injected from the methods on the BasePage.

Results

Windsor - Satisfied all the criteria and has a good case history, blogger community and online documentation. Easy to use and probably the defacto choice. Advanced component creation through Factory facility. Also allowed chaining of individually created containers.

Spring.Net - Verbose and unhelpful documentation and no-obvious / easy for programmable configuration. Did not support generics. Not chosen

Ninject - Easy to use with good clear documentation. Powerful feature set fulfilling all our requirements except container hierarchies so unfortunately was not chosen.

StructureMap - Poorly documented, although had quite an advanced feature set that met all of our requirements, however there was no built-in mechanism for container hierarchies although could be hacked together using for loops see here The lambda expression fluent interface did seem a little over complicated at first, although could be encapsulated away.

Unity - Well documented, easy to use and met all our selection criteria and has an easy extension mechanism to add the pre/post creation eventing mechanism we required. Child containers had to be created from a parent container.

Autofac - Well documented and relatively easy to use, although lambda expression configuration does seem a little over complicated however, again, can be easily encapsulated away. Component scoping is achieved through a "tagging" mechanism and all components are configured up front using a builder which was a little inconvenient. Child containers were created from a parent and assigned components from a "tag". Allowed generic injection.

Conclusion

Our final choice was between Windsor and Unity, and this time around we chose Unity due to its ease of use, documentation, extension system and with it being in "production" status.