NFe.ConvertTxt.ConversaoTXT.SomenteNumeros C# (CSharp) Method

        private string SomenteNumeros(string entrada)
        {
            if (string.IsNullOrEmpty(entrada)) return "";

            StringBuilder saida = new StringBuilder(entrada.Length);
            foreach (char c in entrada)
            {
                if (char.IsDigit(c))
                {
                    saida.Append(c);
                }
            }
            return saida.ToString();
        }