Question

I have this library to compiled to calc.dll.

namespace MyClass
{
    public class Calculator
    {
        public int Value1 {get; set;}
        public int Value2 {get; set;}
        public Calculator()
        {
            Value1 = 100;
            Value2 = 200;
        }

        public int Add(int val1, int val2)
        {
            Value1 = val1; Value2 = val2;
            return Value1 + Value2;
        }
    }
}

I want to instantiate the Calculate class without linking to the calc.dll. Can C# do that? I came up with this code, but I don’t know how to instantiate the Calculator class.

using System;
using System.IO;
using System.Reflection;
using System.Diagnostics;
using System.Collections.Generic;

namespace EX
{
    public class Code
    {
        public static void Test()
        {
            string path = Directory.GetCurrentDirectory();
            string target = Path.Combine(path, @"./myclass.dll");
            Assembly asm = Assembly.LoadFrom(target);

            Calculator h = new Calculator(); // <-- ???
            Type type = h.GetType();
            MethodInfo m = type.GetMethod("Add");

            int res = (int) m.Invoke(h, param);
            Console.WriteLine("{0}", res);
        }

        public static void Main()
        {
            Test();
        }
    }
}

ADDED

I have two solutions, one is from Bala R

        var param = new object[] {100, 200};
        string path = Directory.GetCurrentDirectory();
        string target = Path.Combine(path, @"./myclass.dll");            
        Assembly asm = Assembly.LoadFrom(target);            
        Type calc = asm.GetType("MyClass.Calculator");
        object h  = Activator.CreateInstance(calc);         

        MethodInfo m = calc.GetMethod("Add");            
        int res = (int) m.Invoke(h, param);            
        Console.WriteLine("{0}", res); 

And this one is from agent-j

        string path = Directory.GetCurrentDirectory();
        string target = Path.Combine(path, @"./myclass.dll");
        Assembly asm = Assembly.LoadFrom(target);
        Type type = asm.GetType("MyClass.Calculator");
        ConstructorInfo ctor = type.GetConstructor(Type.EmptyTypes);
        object calc = ctor.Invoke(null);
        MethodInfo m = type.GetMethod("Add");

        var param = new object[] {100, 200};

        int res = (int) m.Invoke(calc, param);
        Console.WriteLine("{0}", res);

Both of them are working, but I kinda prefer Bala’s solution as it’s shorter and getting object h through CreateInstance is more intutive than getting constructor to get object h(calc).

Answer 1

object h = Activator.CreateInstance(asm.FullName, "MyClass.Calculator");

EDIT:

See if this works

Type calc = asm.GetType("MyClass.Calculator)";
object h  = Activator.CreateInstance(calc);