Static helper class for invoking handling methods on AR and AR state.

RedirectToWhen.cs

// snippet is for http://abdullin.com/journal/2011/6/26/event-sourcing-a-la-lokad.html

// simple helper, that looks up and calls the proper overload of
// When(SpecificEventType event). Reflection information is cached statically
// once per type. 
public static class RedirectToWhen
{
    static class Cache<T>
    {
        public static readonly IDictionary<Type, MethodInfo> Dict = typeof(T)
        .GetMethods()
        .Where(m => m.Name == "When")
        .Where(m => m.GetParameters().Length == 1)
        .ToDictionary(m => m.GetParameters().First().ParameterType, m => m);
    }
    public static void InvokeEvent<T>(T instance, IEvent command)
    {
         MethodInfo info;
        var type = command.GetType();
        if (!Cache<T>.Dict.TryGetValue(type, out info))
        {
            var s = string.Format("Failed to locate {0}.When({1})", typeof(T).Name, type.Name);
            throw new InvalidOperationException(s);
        }
        info.Invoke(instance, new[] { command });
    
    }

    public static void InvokeCommand<T>(T instance, ICommand command)
    {
        MethodInfo info;
        var type = command.GetType();
        if (!Cache<T>.Dict.TryGetValue(type, out info))
        {
            var s = string.Format("Failed to locate {0}.When({1})", typeof(T).Name, type.Name);
            throw new InvalidOperationException(s);
        }
        info.Invoke(instance, new[] { command });
    }
}