using System;

public class Program

{

    public static void Main()

    {

        var value1 = 1234.00;

        var value2 = 1234.56;

        var value3 = 34.56;

        var format = "#,###.##";

        Console.WriteLine(value1.ToString(format));

        Console.WriteLine(value2.ToString(format));

        Console.WriteLine(value3.ToString(format));

    }

}