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.