请问为什么简单计算器，无法实现数字相加？

Question

     class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("please input a string");
            string a = Convert.ToString(Console.ReadLine());
            string b = Convert.ToString(Console.ReadLine());
            int i = 0;
          try
           {
                    Console.WriteLine("a+b= {0} + {1}={2}", a, b, a+b);
                }
                catch (FormatException)
                {
                    Console.WriteLine("输入不是整数");
                }
                catch (DivideByZeroException)
                {
                    Console.WriteLine("捕获到了除错误");
                }
                Console.WriteLine("继续");
                Console.ReadKey();
            }
        }

Answer 1

错误 2 无法将类型“System.ConsoleKeyInfo”隐式转换为“int”
 怎么转int？我想实现，ab两数相加，如果ab两个整数非整数，否则捕获该异常

Answer 2

你的a和b都是字符串，改成整数            int a = Convert.ToInt32(Console.ReadLine());
            int b = Convert.ToInt32(Console.ReadLine());