convert转换的使用

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

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            String str = "123";
            int a = Convert.ToInt32(str);
            double b = Convert.ToDouble(str);

            Console.WriteLine(a);
            Console.WriteLine(b);
            Console.ReadKey();




        }
    }
}