这个题目用c#如何编写呀？

using System;

namespace ConsoleApp2
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            var inputX = double.Parse(Console.ReadLine());
            double y;

            if (inputX <= 0)
            {
                y = Math.Abs(inputX) + 3;
            }
            else if (inputX > 0 && inputX < 1)
            {
                y = 1 + Math.Pow(inputX, 2);
            }
            else
            {
                y = 2 * inputX + Math.Sqrt(inputX);
            }

            Console.WriteLine($"y = {y:0.00}");
            Console.ReadKey();
        }
    }
}

using System;

namespace ConsoleApp2
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            var inputChar = Console.ReadKey().KeyChar;

            Console.WriteLine();
            if (char.IsLower(inputChar))
            {
                Console.WriteLine(char.ToUpper(inputChar));
            }
            else if (char.IsUpper(inputChar))
            {
                Console.WriteLine(char.ToLower(inputChar));
            }
            else
            {
                Console.WriteLine(inputChar);
            }

            Console.ReadKey();
        }
    }
}