Castle Windsor: How to specify a constructor parameter from code?

Question

Say I have the following class

MyComponent : IMyComponent {
  public MyComponent(int start_at) {...}
}

I can register an instance of it wit

Answer 1

You need to pass in an IDictionary when you ask the container for the instance.

You'd use this Resolve overload of the IWindsorContainer:

T Resolve<T>(IDictionary arguments)

or the non generic one:

object Resolve(Type service, IDictionary arguments)

So, for example: (assuming container is an IWindsorContainer)

IDictionary<string, object> values = new Dictionary<string, object>();
values["start_at"] = 1;
container.Resolve<IMyComponent>(values);

Note that the key values in the dictionary are case sensitive.

Answer 2

You can use the AddComponentWithProperties method of the IWindsorContainer interface to register a service with extended properties.

Below is a 'working' sample of doing this with an NUnit Unit Test.

namespace WindsorSample
{
    public class MyComponent : IMyComponent
    {
        public MyComponent(int start_at)
        {
            this.Value = start_at;
        }

        public int Value { get; private set; }
    }

    public interface IMyComponent
    {
        int Value { get; }
    }

    [TestFixture]
    public class ConcreteImplFixture
    {
        [Test]
        void ResolvingConcreteImplShouldInitialiseValue()
        {
            IWindsorContainer container = new WindsorContainer();
            IDictionary parameters = new Hashtable {{"start_at", 1}};

            container.AddComponentWithProperties("concrete", typeof(IMyComponent), typeof(MyComponent), parameters);

            IMyComponent resolvedComp = container.Resolve<IMyComponent>();

            Assert.That(resolvedComp.Value, Is.EqualTo(1));
        }

    }
}

Answer 3

Have you considered using Binsor to configure your container? Rather than verbose and clumsy XML you can configure Windsor using a Boo based DSL. Here's what your config will look like:

component IMyComponent, MyComponent:
   start_at = 1

The advantage is that you have a malleable config file but avoid the problems with XML. Also you don't have to recompile to change your config as you would if you configured the container in code.

There's also plenty of helper methods that enable zero friction configuration:

  for type in Assembly.Load("MyApp").GetTypes():
    continue unless type.NameSpace == "MyApp.Services"
    continue if type.IsInterface or type.IsAbstract or type.GetInterfaces().Length == 0
    component type.GetInterfaces()[0], type

You can get started with it here.

Answer 4

You could use a configuration class to read the app.config. Then register that and get windsor to use it for its dependency. Ideally my MyConfiguration would use an interface.

public class MyConfiguration
{
    public long CacheSize { get; }

    public MyConfiguration()
    {
        CacheSize = ConfigurationManager.AppSettings["cachesize"].ToLong();
    }
}



container.Register(Component.For<MyConfiguration>().ImplementedBy<MyConfiguration>());

container.Register(Component.For<MostRecentlyUsedSet<long>>()
.ImplementedBy<MostRecentlyUsedSet<long>>().
DependsOn(Dependency.OnValue("size", container.Resolve<MyConfiguration>().CacheSize))
.LifestyleSingleton());

Answer 5

Edit: Used the answers below code with the Fluent Interface :)

namespace WindsorSample
{
    using Castle.MicroKernel.Registration;
    using Castle.Windsor;
    using NUnit.Framework;
    using NUnit.Framework.SyntaxHelpers;

    public class MyComponent : IMyComponent
    {
        public MyComponent(int start_at)
        {
            this.Value = start_at;
        }

        public int Value { get; private set; }
    }

    public interface IMyComponent
    {
        int Value { get; }
    }

    [TestFixture]
    public class ConcreteImplFixture
    {
        [Test]
        void ResolvingConcreteImplShouldInitialiseValue()
        {
            IWindsorContainer container = new WindsorContainer();

            container.Register(
                Component.For<IMyComponent>()
                .ImplementedBy<MyComponent>()
                .Parameters(Parameter.ForKey("start_at").Eq("1")));

            Assert.That(container.Resolve<IMyComponent>().Value, Is.EqualTo(1));
        }

    }
}

Answer 6

Try this

int start_at = 1; 
container.Register(Component.For().DependsOn(dependency: Dependency.OnValue(start_at)));