输入输出

int num;
num = Convert.ToInt32(Console.ReadLine());

Convert.ToInt32() 把用户输入的数据转换为 int 数据类型，因为 Console.ReadLine() 只接受字符串格式的数据。

// See https://aka.ms/new-console-template for more information
using System;
namespace HelloWorld
{
    class Program
    { 
        static void Main()
        {
            string characterName = "yulin";
            int age = 20;
            Console.WriteLine("There was a person named " + characterName);
            Console.WriteLine("Hello, World!");
            Console.WriteLine("age is  "+ age);
            int num = Convert.ToInt16(Console.ReadLine());
            Console.WriteLine("num is " + num);
        }
    }
}