Question

Looking to cast an Object to a known type at runtime. I have a class (call it Item for ease) which is the base class for Box. Box has it’s own properties as well as the ones from Item (obviously).

Basically I create an instance of Box using the CreateInstance method, this creates an Object of type object but the true type (as witnessed when doing ‘typeof’) is of type Box. I need to cast this Object back to Box without hard coding any switch / if etc. The code I have to test this is below and I’m running out of ideas.

//Base Class
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;
using System.IO;
using System.Xml;
using System.Xml.Serialization;

namespace Test11
{
    public class Item
    {
       public int property1 { get; set; }
       public int property2 { get; set; }
       public int property3 { get; set; }

    public Item()
    {
        property1 = 1;
        property2 = 2;
        property3 = 3;
    }
}

//Box Class - Inherits from Item
namespace Test11
{
    public class Box : Item
    {
        public int property4 { get; set; }

        public Box()
        {
            property4 = 4;
        }
    }
}

//Application Class
namespace Test11
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Item> BaseList = new List<Item>();
            object obj = Assembly.GetExecutingAssembly().CreateInstance("Test11.Box");
            Type t = Type.GetType("Test11.Box");

            //The following line does not work, need to make it work :)
            //BaseList.Add(obj as t); 
            Console.WriteLine(t.ToString());
            Console.ReadLine();
        }
    }
}

I’ve tried many different ways now, the one featured above is one of many. Any ideas or help out there?

Answer 1

Your BaseList is expecting Item objects. You have to cast:

if (obj is Item)
    BaseList.Add((Item)obj);

Or:

if (typeof(Item).IsAssignableFrom(t))
    BaseList.Add((Item)obj);