How to Locate a Service in Unity

Introduction

I spent a considerable amount of time to find a simple example of a Unity service locator implementation on the level of the article written by Josh Smith and finally found it after a long time of searching in a blog post back in 2009. I re-post this content here with some hopefully helpful comments. Please be sure to read Josh's article if you are new to the service location pattern.

Using the Code

Just create a Console Type project and add the Unity package via Nuget. Next, you should be able to copy/paste the code below to inspect how things work on a simple object registration/resolution level in Unity.

    using Microsoft.Practices.ServiceLocation;
    using Microsoft.Practices.Unity;
    using System;

    /// <summary>
    /// Implements an interface for testing
    /// </summary>
    interface IFoo
    {
    }

    /// <summary>
    /// Implements a test class based on the <seealso cref="IFoo"/> interface.
    /// This code requires the Unity package to be installed (e.g.: via Nuget).
    /// </summary>
    public class Foo : IFoo
    { }

    /// <summary>
    /// Source: https://blogs.msdn.microsoft.com/miah/2009/05/12/servicelocator-and-unity-be-careful/
    /// </summary>
    class Program
    {
        static void Main(string[] args)
        {
            UnityServiceLocator locator = new UnityServiceLocator(ConfigureUnityContainer());
            ServiceLocator.SetLocatorProvider(() => locator);

            Console.WriteLine(Resolve());
            Console.ReadKey();
        }

        /// <summary>
        /// Asks the Unity ServiceLocator to resolve two registered instances
        /// and determines whether they are equal or not.
        /// </summary>
        /// <returns>True if all resolved instances are the same, otherwise false</returns>
        private static bool Resolve()
        {
            var a = ServiceLocator.Current.GetInstance<IFoo>();
            var b = ServiceLocator.Current.GetInstance<IFoo>();

            return a.Equals(b);
        }

        /// <summary>
        /// Constructs and configures a <seealso cref="IUnityContainer"/> and returns it.
        /// </summary>
        /// <returns></returns>
        private static IUnityContainer ConfigureUnityContainer()
        {
            UnityContainer container = new UnityContainer();

            //container.RegisterType<IFoo, Foo>(new ContainerControlledLifetimeManager());
            container.RegisterInstance<IFoo>(new Foo());

            return container;
        }
    }

Points of Interest

Service Location is a must have pattern when it comes to architecturing large applications. Be sure to understand and apply this pattern whenever a service seems to be rightfully used in any application, be it Windows Form, WPF, UWP, or any other framework, or type of application.