Getting started with unity-container

Installation

In order to get started, you just need to install the Unity nuget package. Run the following command from the package manager console:

PM> Install-Package Unity

Alternatively, you can use Visual Studio to install Unity on a particular project using the Manage NuGet Packages for Solution option under Tools -> NuGet Package Manager.

Hello World 

interface IGreeter
{
    void Greet();
}

class Greeter : IGreeter
{
    public void Greet()
    {
        Console.WriteLine("Hello World");
    }
}

class SpanishGreeter : IGreeter
{
    public void Greet()
    {
        Console.WriteLine("Hola Mundo");
    }
}

class FrenchGreeter : IGreeter
{
    public void Greet()
    {
        Console.WriteLine("Bonjour le Monde");
    }
}

class Program
{
    static void Main(string[] args)
    {
        var container = new UnityContainer()
            .RegisterType<IGreeter, SpanishGreeter>("spanish")
            .RegisterType<IGreeter, FrenchGreeter>("french")
            .RegisterType<IGreeter, Greeter>();

        //Get default registration. Outputs "Hello World"
        var greeter = container.Resolve<IGreeter>();
        greeter.Greet();

        //Get specific named registration. Outputs "Hola Mundo"
        greeter = container.Resolve<IGreeter>("spanish");
        greeter.Greet();

        //Get all named registrations (excludes the default one)
        //Outputs "Hola Mundo" and "Bonjour le Monde"
        foreach (var g in container.ResolveAll<IGreeter>())
        {
            g.Greet();
        }

        Console.ReadLine();
    }
}

Constructor Injection 

interface IService
{
    void ProcessRequest();
}

interface IRepository
{
    IEnumerable<string> GetData();
}

class HelloWorldRepository : IRepository
{
    public IEnumerable<string> GetData()
    {
        return new[] { "Hello", "World" };
    }
}

class HelloWorldService : IService
{
    private readonly IRepository repo;
    public HelloWorldService(IRepository repo)
    {
        this.repo = repo;
    }
    public void ProcessRequest()
    {
        Console.WriteLine(String.Join(" ", this.repo.GetData()));
    }
}

class Program
{
    static void Main(string[] args)
    {
        var container = new UnityContainer()
            .RegisterType<IRepository, HelloWorldRepository>()
            .RegisterType<IService, HelloWorldService>();

        //Unity automatically resolves constructor parameters that knows about.
        //It will return a HelloWorldService with a HelloWorldRepository
        var greeter = container.Resolve<IService>();
        //Outputs "Hello World"
        greeter.ProcessRequest();            

        Console.ReadLine();
    }
}
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