using System;

public class Program

{

    public static void Main()

    {

        // console string template

        Console.WriteLine("hi {0}, this is a {1}","Lee","Book");

        // string template C# 7.0

        // 如果 {變數} 不存在，在編譯階段就會不通過

        string Name = "Tom", Item = "Book" , NULL = null;

        string s = $"Hi {Name}, this is a {Item}. {NULL}";

        Item = "Apple";

        Console.WriteLine(s);

    }

}