System.Data.ExpressionParser.IsDigit C# (CSharp) Метод

        private bool IsDigit(char ch)
        {
            //single comparison
            switch (ch)
            {
                case '0':
                case '1':
                case '2':
                case '3':
                case '4':
                case '5':
                case '6':
                case '7':
                case '8':
                case '9':
                    return true;
                default:
                    return false;
            }
        }