Simple Behavior Graph

BehaviorGraph.cs

public interface IBehavior
{
    void Execute<T>(T data);
}

public class BehaviorGraph
{
    private readonly IList<Type> _behaviors = new List<Type>();

    public T Execute<T>()
    {
        return Execute(default(T));
    }

    public T Execute<T>(Func<IBehavior, Type, IBehavior> factory)
    {
        return Execute(default(T), factory);
    }

    public T Execute<T>(T data)
    {
        return Execute(data, (b, t) => (IBehavior)Activator.CreateInstance(t, new object[] {b}));
    }

    public T Execute<T>(T data, Func<IBehavior, Type, IBehavior> factory)
    {
        var result = new ResultBehavior();
        _behaviors.Aggregate(result, factory).Execute(data);
        return (T)result.Data;
    }

    public BehaviorGraph WrapBehavior<TBehavior>() where TBehavior : IBehavior
    {
        _behaviors.Add(typeof(TBehavior));
        return this;
    }

    private class ResultBehavior : IBehavior
    {
        public object Data { get; private set; }
        public void Execute<T>(T data)
        {
            Data = data;
        }
    }
}

BehaviorGraphTests.cs

[TestFixture]
public class BehaviorGraphTests
{
    private class Behavior : IBehavior
    {
        private readonly IBehavior _innerBehavior;
        private readonly string _value;

        public Behavior(IBehavior innerBehavior, string value)
        { _innerBehavior = innerBehavior; _value = value; }

        public void Execute<T>(T data) { _innerBehavior.Execute(data + _value); }
    }

    private class Behavior1 : Behavior
    { public Behavior1(IBehavior innerBehavior) : base(innerBehavior, "1") { } }

    private class Behavior2 : Behavior
    { public Behavior2(IBehavior innerBehavior) : base(innerBehavior, "2") { } }

    private class Behavior3 : Behavior
    { public Behavior3(IBehavior innerBehavior) : base(innerBehavior, "3") { } }

    [Test]
    public void should_execute_behaviors_in_order()
    {
        new BehaviorGraph()
            .WrapBehavior<Behavior2>()
            .WrapBehavior<Behavior1>()
            .WrapBehavior<Behavior3>()
            .Execute("hai")
            .ShouldEqual("hai312");
    }
}