C#数字前面如何补0

PadLeft()函数：向左补齐
PadRight()函数：向右补齐

 class Program
    {
        static void Main(string[] args)
        {
            int a = ;
            Console.WriteLine(a.ToString().PadLeft(,''));   //向左补齐
            Console.WriteLine(a.ToString().PadRight(, '')); //向右补齐
            Console.ReadKey();
        }
    }