Reflection C#Activator返回null值

Question

请我不知道我做错了,当我运行此代码,我得到一个异常:值不能为空....当我在调试模式下运行它,我看到"calculatorInstance"变量为空.请帮帮我.

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

namespace ReflectionWithLateBinding
{
    public class Program
    {
        static void Main()
        {
            //load the current executing assembly
            Assembly executingAssembly = Assembly.GetExecutingAssembly();

            //load and instantiate the class dynamically at runtime - "Calculator class"
            Type calculatorType = executingAssembly.GetType("ReflectionWithLateBinding.Calculator");


            //Create an instance of the type --"Calculator class"
            object calculatorInstance = Activator.CreateInstance(calculatorType);

            //Get the info of the method to be executed in the class
            MethodInfo sumArrayMethod = calculatorType.GetMethod("SumNumbers");

            object[] arrayParams = new object[2];

            arrayParams[0] = 5;
            arrayParams[1] = 8;
            int sum;
            sum = (int)sumArrayMethod.Invoke(calculatorInstance, arrayParams);

            Console.WriteLine("Sum = {0}",  sum);

            Console.ReadLine();

        }



        public class Calculator
        {
            public int SumNumbers(int input1, int input2)
            {
                return input1 + input2;
            }
        }
    }
}

Answer 1

我很确定它实际上GetType是返回的方法null- 因为没有具有完全限定名称的类型ReflectionWithLateBinding.Calculator.你的Calculator班级嵌套在你的Program班级里.

它的调用Activator.CreateInstance是抛出一个异常,因此calculatorInstance永远不会进行赋值- 它不是变量的值null,而是它的声明语句(包括初始化程序)永远不会完成.

选项(不要两者兼得!):

• 移动类,以便它不是在内部Program类(即所以它直接声明的命名空间)
• 将您的GetType通话更改为executingAssembly.GetType("ReflectionWithLateBinding.Program+Calculator")