Dynamic Type Conversion in C#

Question

I have a lot of lists of different types, and a dictionary that stores for each type the according list. I would like to add an item to the list of its type:

    class Demo
    {
        [Serializable] class A{}
        [Serializable] class B{}
        [Serializable] class Z{}

        List<A> a = new List<A>();
        List<B> b = new List<B>();
        List<Z> z = new List<Z>();

        Dictionary<Type, object> dict;

        Demo()
        {
            dict = new Dictionary<Type, object>
            {
                {typeof(List<A>), a},
                {typeof(List<B>), b},
                {typeof(List<Z>), z},
            };
        }

        void Add(dynamic items)
        {
            var type = items.GetType();         
            dynamic list = dict[type];          
            list.AddRange( items );
        }
        
        

        static void Main()
        {
            var demo = new Demo();
            var json = JsonConvert.SerializeObject(new List<B>(){new B()});
            var type = typeof(List<B>);

            //compiler has no information of the type of item
            //the type used for deserialization is not known at compile time
            var item = JsonConvert.DeserializeObject(json, type );
            demo.Add(item);                     
        }
    }

This is working, but I wonder whether there is a solution without using the dynamic type - Is there a way to convert the entry in the dictionary to List<T>, or do you have another idea how to solve this problem dynamically without dynamic?

Please note that I cannot use

void Add<T>( T item ) {...}

Since the compile-time-type of the item is object, for instance from

object item = JsonConvert.DeserializeObject( json , item_type );

Answer 1

use reflection:

void Add(object items)
{
    var type = items.GetType();
    var method = type.GetMethod("AddRange");
    var list = dict[type];                                              
    var ret = method.Invoke(list, new object[]{items} );
}