using System;

​

public class Program

{

    public static void Main(string[] args)

    {

        var number1 = 66.2356d;

        var number2 = 66d;

        var string1 = number1.ToString("N1"); 

        var string2 = number2.ToString("N1"); 

        Console.WriteLine(string1);

        Console.WriteLine(string2);

    }

}