[C#/COMMON] 선행 0을 추가해 값 문자열 출력하기

using System;

int value1 = 15;

Console.WriteLine(value1.ToString("0000"));
Console.WriteLine(value1.ToString("D4"));
Console.WriteLine($"{value1:0000}");

int value2 = -15;

Console.WriteLine(value2.ToString("0000"));
Console.WriteLine(value2.ToString("D4"));
Console.WriteLine($"{value2:0000}");