Dependency Injection with Autofac: Registration Ordering

This post will be part of on going series for Dependency Injection with Autofac. If you have not gone through my previous post I would encourage you to go through it. Followings are links for that.

Dependency Injection with Autofac – Getting Started
Dependency Injection with Autofac – Constructor Injection
Dependency Injection with Autofac- Modules Feature

In this this blog we are going to learn about Registration ordering in Autofac.  If you register same interface multiple times then by default the last registration will be preserved. So when you resolve things it will be resolved by last registration. You can also prevent that via “PreserveExistingDefaults” method which is a second behaviour where first registration will be preserved. We will look both in details in this post.

Registration Ordering:

To demonstrate registration ordering, We are going to create a simple Employee class like below.

After creating a Employee class following is a code for my console application.

If you see code carefully, The important thing is two functions “DefaultBehaviour” and “AnotherBehaviour”. First function I’ve register two employee object one by one then. I tried to resolve employee object and with the help of "PrintEmployee" method I have printed Employee object.  Here I’ve used default behaviour so it will print secondEmployee as last registration will be resolved.

While in “AnotherBehaviour” function, I have used “PreserveExistingDefaults” function while registering secondEmployee object. So it will preserve first registration. So when you resolve object it will resolve first registration. So when you print employee object with “PrintEmployee” method it will print firstEmployee object.

When you run this console application. Following will be output as expected.



That’s it. Hope you like it. Stay tuned for more!.

You can find complete source code this Autofac series on Github at - https://github.com/dotnetjalps/AutofacSamples

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Dependency Injection with Autofac : Modules feature

I’m having fun with Autofac as IOC containers and this is third post in series. In this blog post we are going to learn about Autofac modules. If you have not gone through first two blog posts then I would encourage you to go through it. Followings are link for that.

Dependency Injection with Autofac- Getting Started
Dependency Injection with Autofac – Constructor Injection

What is Autofac Modules?

Autofac modules provides greater flexibility  for structuring large application. Register all the component in single class will work for small applications. But for larger applications that will be quite difficult class. In this situation Autofac modules can help.  Autofac modules allow us to break registrations of component in different classes. Then later all you can load all the modules at single places.

So what we are waiting for, Let’s write some code to demonstrate the power of Autofac Modules. For that I’ve created a simple console application called “AutofacModules” and added Autofac nuget package to get reference of application. In this application we are going to create two separate module for “Student” and “Teachers”. So lets start by creating student model class like following.


Following is a student repository interface which contains a "Print" Method to print Student.
 And here is the implementation for Student Repository Inteface.

Now it's time to create Teacher model class like following.

Following is a interface created for Teacher repository which contains "Print" Method to print Teacher.
And here is the implementation of Teacher repository interface.
Now we are done with creating basic classes and interfaces for Student and Teacher It's time to create a modules for them. To created a module for them we need to create a separate class for Teacher and Student Module which got inherited from the Autofac module class. Following is a code of Student module.
And same for teacher module.
 If you see code of both classes carefully then you will realize that it is inherited from the Module classes and It's got a Load method override where we have done registration of repositories. Now our modules are also ready so It's time to write our main console application code. Following is a code for that.
If you see above code carefully the important thing is "BuildContainer" method where I've registered our module with RegisterModule method.Rest I have created teacher and student object and created object with Autofac Container and print respective objects. When you run application following is a output as expected.



That’s it. Hope you like it. Stay tuned for more post about Autofac features.

You can find whole source code of this Autofac series at Github on following location -https://github.com/dotnetjalps/AutofacSamples

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Dependency Injection with Autofac : Constructor Injection

Recently I’m playing with Autofac and I’m having fun with it. This blog post a part of same series. In this blog post we are going to look into how we can do constructor injection with Autofac. If you are not familiar with Autofac you can go through my introductory blog at following location.

Dependency Injection with Autofac: Getting Started

In this blog, We are going to see how we can do constructor injection with Autofac. So for that I’ve created a small console application. After creating a application, first thing you need to do is to add reference of Autofac via Nuget Package. You can do that via following nuget package.



Now it’s time to write some code. I’ve created a sample basic “Employee” model class like following.



After that I’ve created a interface “IEmployeeRepository” which has one method to print employee and expects Employee object parameter.


And following is a implementation class for Employee Repository.


Now it’s time to write Employee Service class code like following.


If you see above class carefully, You can see that it’s expect a constructor parameter of Employee Repository parameter and there we need to constructor injection.  So let’s write some Autofac code for constructor injection like following.


Here in the above code, You can see I have “BuildContainer” static method. Which created a Container Builder object and It’s register type of employee repository and employee service and it’s return a container object. In main method code I’ve resolve employee service class object with container and it’s automatically inject our constructor requirement of employee service class. Then I’ve created a employee class object and print it with print method. Once you run the application. You will get following output as expected.



That’s it. You can see it’s very easy to do constructor injection with Autofac. In future post we are going to look at some other features provided by Autofac. Stay tuned for more.

You can find complete example of above blog post at following location on github- https://github.com/dotnetjalps/AutofacSamples

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