Skip to main content

Injecting AutoMapper with IoC

Update - 14th February 2016:
Looking in my blog stats, this continues to be one of my most popular articles, so it is most definitely worth an update. As of v4.2.0 Automapper has been updated to remove the static implementation. I've not had chance to play with the new version yet but I would imagine this version will now work with any IoC container you wish to use it with.

Original Article:
The main “Mapper” class of the AutoMapper framework is a static class which does make the initial testing and usage really easy but quickly causes problems if you’re using an Inversion of Control framework such as a Castle Windsor.  Also being static it is far harder to abstract the AutoMapper framework out of any unit tests using mocking frame such as MOQ.  As a final point for all these reasons using AutoMapper directly could cause problems in the future if it was decided to switch to another mapping framework.
The following code handles all of the above concerns / issues by wrapping the AutoMapper static instance up into a single bespoke mapping class.  At a first glance this would appear to be a step backwards as it requires each object to object mapping to be defined as a method in the interface and implementing class.   However for very little overhead or extra coding this comes with a benefit of abstracting the “how” of the mapping from the calling code.  It would be easy to add another mapping framework into the Mapper class below and then update individual methods to use that new mapping framework.  It also helps prevent any premature optimisations as the code can be deployed with new methods using mappings that provide the maximum automation and minimal manual configuration.  If performance issues then arise during testing or live usage, individual methods/mappings can be tackled to provide better performance – which for maximum throughput if the situation required it could result in the mapping framework(s) being by-passed completely and all initialisation of the target class performed directly within the mapping method.

using am = Automapper;

namespace Tools


public interface IMapper


CustomerEntity MapCustomer(CreateCustomerMsg msg);

CustomerEntity MapCustomer(UpdateCustomerMsg msg);

public class Mapper : IMapper


static Mapper()


// All creation code in the static constructor
am.Mapper.CreateMap<CreateCustomerMsg, CustomerEntity>();
am.Mapper.CreateMap<UpdateCustomerMsg, CustomerEntity> ();
public CustomerEntity MapCustomer(CreateCustomerMsg msg)
return am.Mapper.Map<CreateCustomerMsg,CustomerEntity>(msg);
public CustomerEntity MapCustomer(UpdateCustomerMsg msg);
return am.Mapper.Map<(UpdateCustomerMsg,CustomerEntity>(msg);
} Tags: ,,


Popular posts from this blog

Mocking HttpCookieCollection in HttpRequestBase

When unit testing ASP.NET MVC2 projects the issue of injecting HttpContext is quickly encountered.  There seem to be many different ways / recommendations for mocking HttpContextBase to improve the testability of controllers and their actions.  My investigations into that will probably be a separate blog post in the near future but for now I want to cover something that had me stuck for longer than it probably should have.  That is how to mock non abstract/interfaced classes within HttpRequestBase and HttpResponseBase – namely the HttpCookieCollection class.   The code sample below illustrates how it can be used within a mocked instance of HttpRequestBase.  Cookies can be added / modified within the unit test code prior to being passed into the code being tested.   After it’s been called, using a combination of MOQ’s Verify and NUnit’s Assert it is possible to check how many times the collection is accessed (but you have to include the set up calls) and that the relevant cookies have …

Injecting HttpContextBase into an MVC Controller

It is a shame that when the ASP.NET MVC framework was released they did not think to build IoC support into the infrastructure. All the major components of the MVC engine appear to magically inherit instances of HttpContext and it’s related objects – which can cause no end of problems if you are trying to utilise Unit Testing and IoC. Reading around various articles on the subject just to get around this one problem requires the implementation of several different concepts and you are still left with a work around. The code below, along with the other links referenced in this article is my stab at resolving the issue. There’s probably nothing new here, but it does attempt to relate all the information needed to do this for Castle Windsor. The overview is that all controllers will need to inherit from a base controller, which takes an instance of HttpContext into it’s constructor. It then overrides the property HttpContext in the main controller class, supplying it’s own version…

Unit Testing Workflow Code Activities - Part 1

When I first started looking into Windows Workflow one of the first things that I liked about it was how it separated responsibilities. The workflow was responsible for handling the procedural logic with all it's conditional statements, etc. Whilst individual code activities could be written to handle the business logic processing; created in small easily re-usable components. To try and realise my original perception this series of blog posts will cover the unit testing of bespoke code activities; broken down into: Part One: Unit testing a code activity with a (generic) cast return type (this post)Part Two: Unit testing a code activity that assigns it's (multiple) output to "OutArguments" (Not yet written)So to make a start consider the following really basic code activity; it expects an InArgument<string> of "Input" and returns a string containing the processed output; in this case a reverse copy of the value held in "Input".namespace Ex…