Create Instance for a generic type with arguments for constructor

ActivatorExt.cs

public static class ActivatorExt

    {

        private static ObjectActivator<T> GetActivator<T>(ConstructorInfo ctor)

        {

            var paramsInfo = ctor.GetParameters();



            var param = Expression.Parameter(typeof(object[]), "args");



            var argsExp = new Expression[paramsInfo.Length];



            for (var i = 0; i < paramsInfo.Length; i++)

            {

                Expression index = Expression.Constant(i);

                var paramType = paramsInfo[i].ParameterType;



                Expression paramAccessorExp = Expression.ArrayIndex(param, index);



                Expression paramCastExp = Expression.Convert(paramAccessorExp, paramType);



                argsExp[i] = paramCastExp;

            }



            var newExp = Expression.New(ctor, argsExp);



            var lambda = Expression.Lambda(typeof(ObjectActivator<T>), newExp, param);



            var compiled = (ObjectActivator<T>) lambda.Compile();

            return compiled;

        }



        public static T CreateInstance<T>(params object[] args)

        {

            var ctor = typeof(T).GetConstructors().First();

            var createdActivator = GetActivator<T>(ctor);

            return createdActivator(args);

        }



        private delegate T ObjectActivator<out T>(params object[] args);

    }