C#常用的对象实例化有以下几种方式：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text;

namespace Demo
{
    class Program
    {
        static void Main(string[] args)
        {
            //通过new实例化
            Calculate calc = new Calculate();
            Console.WriteLine(calc.AddOne(0));

            //通过Activator实例化
            ICalculate calc2 = Activator.CreateInstance<Calculate>();
            Console.WriteLine(calc2.AddOne(1));
            ICalculate calc3 = (Calculate)Activator.CreateInstance(Type.GetType("Demo.Calculate"));  
            Console.WriteLine(calc3.AddOne(2));

            //通过Assembly实例化
            ICalculate calc4 = (Calculate)Assembly.GetAssembly(Type.GetType("Demo.Calculate")).CreateInstance("Demo.Calculate");
            Console.WriteLine(calc4.AddOne(3));

            //Type.GetType("Demo.Calculate")也可以写成typeof(Calculate)
        }
    }

    public class Calculate : ICalculate
    {
        public int AddOne(int a)
        {
            return a + 1;
        }
    }

    public interface ICalculate
    {
         int AddOne(int a);
    }
}