Kata example for IoC

Container.cs

   public class Container
    {
        private readonly Dictionary<Type, Type> _simpleMappings = new Dictionary<Type, Type>();

        public T Create<T>()
        {
            return (T) Create(typeof (T));
        }

        public object Create(Type t)
        {
            var ctors = t.GetConstructors();
            var biggestCtor = ctors.First();
            var max = 0;
            foreach (var ctor in ctors.Where(ctor => ctor.GetParameters().Length > max))
            {
                biggestCtor = ctor;
            }

            var dependencies = new List<object>();

            foreach (var dep in biggestCtor.GetParameters())
            {
                var typeToCreate = SelectType(dep.ParameterType);
                var depInstance = Create(typeToCreate);
                dependencies.Add(depInstance);
            }

            return biggestCtor.Invoke(dependencies.ToArray());
        }

        private Type SelectType(Type parameterType)
        {
            if (!parameterType.IsInterface)
            {
                return parameterType;
            }

            var candidateImplementations = parameterType.Assembly.GetTypes()
                .Where(x => !x.IsInterface && x.GetInterfaces().Contains(parameterType))
                .ToList();

            if (candidateImplementations.Count == 0)
            {
                throw new NotEnoughCandidatesException();
            }

            if (candidateImplementations.Count == 1)
            {
                return candidateImplementations.First();
            }

            if (_simpleMappings.ContainsKey(parameterType))
            {
                return _simpleMappings[parameterType];
            }

            throw new TooManyCandidatesException();
        }

        public Container For<TIface, TInstance>()
        {
            _simpleMappings.Add(typeof(TIface), typeof(TInstance));
            return this;
        }
    }
   
   public class TooManyCandidatesException : Exception
    {
    }
    
    public class NotEnoughCandidatesException : Exception
    {
    }