Stencil Micro IoC Container

Stencil is a micro Inversion of Control container. It was written with the following design goals in mind:

• A single file with no dependencies outside the .NET 4.0 Client Profile
• Support for property injection via public interfaces
• For use in small projects without the need to take any dependencies

##Configuration

Using stencil is easy. Copy and paste the Stencil.cs file into your project. The container can be accessed via a built-in Singleton or by creating a new instance of the Stencil class.

// Using the Singleton
var foo = Stencil.Instance.Resolve<IFoo>();

// Creating a new instance
var stencil = new Stencil();
stencil.Initialize();

var bar = stencil.Resolve<IBar>();

By default, Stencil will scan the executing assembly for all interfaces. You can specify additional assemblies to search by adding them to the Assemblies collection in the Defaults class. A static Defaults class exists on the Stencil object for use by the Singleton, or in the event no parameters are supplied when calling the Initialize() method.

// Configuring assemblies to be scanned
Stencil.Defaults.Assemblies.Add(typeof(Foo).Assembly);
Stencil.Defaults.Assemblies.Add(typeof(Bar).Assembly);

// Configuring object resoluton options
var defaults = new Defaults
{
    UsePropertyInjection = true,
    UseSingletons = true
};

var stencil = new Stencil();
stencil.Initilize(defaults);

Setting flags for UsePropertyInjection and UseSingletons determine the behavior of objects that are resolved from the container.

##Usage

You can access items from the container by calling the Resolve() method.

public interface IFoo
{
    string SayFoo();
}

public class Foo : IFoo
{
    public string SayFoo()
    {
        return "foo";
    }
}
  	
var foo = Stencil.Instance.Resolve<IFoo>();

##Property Injection

If the object resolved from by the container has any public properties with interfaces known by the container, these are initialized.

public interface IBar
{
    string SayBar();
}

public class Bar : IBar
{
	// Set by container
    public IFoo Foo { get; set; }

    // Set to null
    public IBar RecursiveBar { get; set;}

    public string SayBar()
    {
        return Foo.SayFoo();
    }
}

var bar = Stencil.Instance.Resolve<IBar>();

Assert.AreEqual("foo", service.SayBar());

If a child object references a parent, the value of the parent is set to null.

##Generic Lists

Generic lists are supported for properties implementing an IList. The list is instantiated with all objects in the container matching the declared interface. This is useful for implementing Visitor and Chain-of-responsibility patterns.

public interface IFizzBuzz
{
    string SayFizzBuzz();
}

[Order(1)]
public class Fizz : IFizzBuzz
{
    public string SayFizzBuzz()
    {
        return "fizz";
    }
}

[Order(2)]
public class Buzz : IFizzBuzz
{
    public string SayFizzBuzz()
    {
        return "buzz";
    }
}

public class FizzBuzz
{
    public IList<IFizzBuzz> FizzBuzzers { get; set; }
}

var fizzbuzz = Stencil.Instance.Resolve<FizzBuzz>();

Assert.AreEqual(2, fizzbuzz.FizzBuzzers.Count);
Assert.AreEqual("fizz", fizzbuzz.FizzBuzzers[0].SayFizzBuzz());
Assert.AreEqual("buzz", fizzbuzz.FizzBuzzers[1].SayFizzBuzz());

If order is import when instantiating the list, an Order attribute allows you to specify the order of the list items. This is optional, and not required if order is unimportant.