using System.Globalization;

using System.Text.RegularExpressions;

using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(Ext.IsNumeric("1")); //True

        Console.WriteLine(Ext.IsNumeric("a")); //False

        Console.WriteLine(Ext.IsNumeric("1.0")); //False

        Console.WriteLine(Ext.IsNumeric("1.0", true)); //False

​

        Console.WriteLine(Ext.IsNumeric("+1.0", true)); //False

        Console.WriteLine(Ext.IsNumeric("-1.0", true)); //False

        Console.WriteLine(Ext.IsNumeric("+1.0", true, true)); //True

        Console.WriteLine(Ext.IsNumeric("-1.0", true, true)); //True

        Console.WriteLine(Ext.IsNumeric("1,0", true)); //False

        Console.WriteLine(Ext.IsNumeric("1,0", true, false, true)); //True

        Console.WriteLine(Ext.IsNumeric("1.000,00", true, false, true)); //True

    }

}

public static class Ext{

        public static CultureInfo USCultureInfo => new CultureInfo("EN-US");

        public static CultureInfo BRCultureInfo =>  new CultureInfo("pt-BR");

        public static bool IsNumeric(this string aString, bool EhFoat = false, bool PermitirNegativo = false, bool EhFormatoBR = false)

        {

            if (string.IsNullOrEmpty(aString))

            {

                return false;

            }

​

            if (!EhFoat)

            {

                return Regex.IsMatch(aString, "^\\d{1,}$", RegexOptions.Singleline);

            }

​

            var Provider = (EhFormatoBR) ? BRCultureInfo : USCultureInfo;

​

            var Options = NumberStyles.AllowDecimalPoint;

            if (PermitirNegativo)

            {

                Options = Options | NumberStyles.AllowLeadingSign;

            }

​

            if (EhFormatoBR)

            {

                Options = Options | NumberStyles.AllowThousands;

            }

​

            return decimal.TryParse(aString, Options, Provider, out _);

​

​

        }

    }