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Simplified autofac registrations

, 28 Oct 2010
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Simplified autofac registrations

I'm building an application which will monitor other applications (memory using, start them if they crash, etc). I'm trying to stop re-inventing the wheel (ohhh, it’s fun to do everything yourself) and start using other components. This time I needed an IoC container and autofac seemed like a good match for me.

To simplify IoC registration, I created an attribute which I use on all my components. In this way, I don't have to remember to register each component, it’s done with the help of the attribute.

Using the attribute without constructor parameters will register the component with all interfaces.

[Component]
class MyComponent : IConsumer<MonitorEvent>, ISomeService
{
    //[....]
}

While using the constructor will only register one interface.

[Component(typeof(ISomeService)]
class MyComponent : IConsumer<MonitorEvent>, ISomeService
{
    //[....]
}

The autofac registration looks like this:

internal class Program
{
    public static IContainer Components { get; private set; }

    private static void Main(string[] args)
    {
        var builder = new ContainerBuilder();

        //i = interface type, c = concrete type
        Assembly[] assemblies = AppDomain.CurrentDomain.GetAssemblies();
        assemblies.Each(assembly => assembly.FindComponents((i, c) => 
			builder.RegisterType(c).As(i).SingleInstance()));

        Components = builder.Build();
    }
}

Quite smooth, huh?

Extension methods making it possible:

public static class ComponentFinder
    {
        public static void Each<T>(this IEnumerable<T> enumerable, Action<T> action)
        {
            foreach (T item in enumerable)
                action(item);
        }

        public static void FindComponents
		(this Assembly assembly, Action<Type, Type> action)
        {
            Type componentAttribute = typeof (ComponentAttribute);
            foreach (Type type in assembly.GetTypes())
            {
                object[] attributes = type.GetCustomAttributes(componentAttribute, false);
                if (attributes.Length == 0)
                {
                    type.GetInterfaces().Each(i => action(i, type));
                    continue;
                }

                foreach (object attribute in attributes)
                {
                    Type interfaceType = 
			((ComponentAttribute) attribute).InterfaceType ?? type;
                    action(interfaceType, type);
                }
            }
        }
    }

Getting components is done by the resolve method:

Program.Components.Resolve<IMyService>.SendMessage("Hello world");

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License

This article, along with any associated source code and files, is licensed under The GNU Lesser General Public License (LGPLv3)

About the Author

jgauffin
Founder Gauffin Interactive AB
Sweden Sweden
Founder of OneTrueError, a .NET service which captures, analyzes and provide possible solutions for exceptions.
 
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Comments and Discussions

 
GeneralMy vote of 5 PinmemberMichał Zalewski28-Oct-10 15:41 

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