using System;

using System.Drawing;

using System.Text.Json;

using Newtonsoft.Json;

using System.Globalization;

public class Program

{

    public static void Main()

    {

        var amount = 12345.0000M;

        var cultureInfo = CultureInfo.GetCultureInfo("en-US");

        var formattedAmount = String.Format(cultureInfo, "{0:N2}", amount);

        Console.WriteLine(formattedAmount);

        Console.ReadLine();

    }

}