using System;

namespace Lesson_One
{
    class Program
    {
        static void Main(string[] args)
        {
            // ========== 变量 ==========
            int age = 25;
            double height = 175.5;
            string name = "无言势字幕";
            char grade = 'A';
            bool isActive = true;

            Console.WriteLine("=== 变量 ===");
            Console.WriteLine($"姓名: {name}");
            Console.WriteLine($"年龄: {age}");
            Console.WriteLine($"身高: {height}cm");
            Console.WriteLine($"等级: {grade}");
            Console.WriteLine($"状态: {isActive}");

            // ========== var 自动推断 ==========
            Console.WriteLine("\n=== var 自动推断 ===");
            var message = "这是 string 类型";
            var number = 42;  // 推断为 int
            Console.WriteLine($"message 是: {message.GetType()}");
            Console.WriteLine($"number 是: {number.GetType()}");

            // ========== 常量 ==========
            Console.WriteLine("\n=== 常量 ===");
            const int MAX_RETRY = 3;
            const string VERSION = "v1.0";
            Console.WriteLine($"最大重试次数: {MAX_RETRY}");
            Console.WriteLine($"版本: {VERSION}");

            // ========== 类型转换 ==========
            Console.WriteLine("\n=== 类型转换 ===");
            int i = 10;
            double d = i;  // 隐式转换
            Console.WriteLine($"int -> double: {d}");

            double d2 = 3.14;
            int i2 = (int)d2;  // 显式转换
            Console.WriteLine($"double -> int: {i2}");

            string s = i.ToString();
            Console.WriteLine($"int -> string: {s}");

            int i3 = int.Parse("123");
            Console.WriteLine($"string \"123\" -> int: {i3}");

            // ========== 输入练习 ==========
            Console.WriteLine("\n=== 输入练习 ===");
            Console.Write("请输入你的名字: ");
            string inputName = Console.ReadLine();
            Console.Write($"你好, {inputName}! ");

            Console.Write("请输入年龄: ");
            string ageInput = Console.ReadLine();
            int userAge = int.Parse(ageInput);
            Console.WriteLine($"你 {userAge} 岁了");

            Console.ReadLine();
        }
    }
}