using System.Globalization;

​

public class Program {

    public static void Main() {

        var minhaCultura = new CultureInfo("pt-BR"); 

        minhaCultura.DateTimeFormat.ShortDatePattern = "dd/MM/yyyy";

        minhaCultura.DateTimeFormat.ShortTimePattern = "HH:mm";

        minhaCultura.NumberFormat.NumberDecimalDigits = 2;

        minhaCultura.NumberFormat.NumberGroupSeparator = "_";

        minhaCultura.NumberFormat.NumberDecimalSeparator = ",";

        System.Console.WriteLine(string.Format(minhaCultura, "{0:N}", 43239.11));

    }

}