1.ダイナミックタイプ

2.プロジェクト

using System;
using static System.Console;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Diagnostics;
using System.Reflection;

namespace testProject
{
   
    
    class Program
    {         
        static void Main(string[] args)
        {
            dynamic x;
            x = 1_234;
            WriteLine($"{x} - {x.GetType()}");
            x = "Dynamic Type!";
            WriteLine($"{x} - {x.GetType()}");

            string ss = "Hello";
            WriteLine(ss.Length);

            var vs = "Hello";
            WriteLine(vs.Length);

            dynamic ds = "Hello";
            WriteLine(ds.Length);
        }
    }
}