Decimal

 server---

    public string Conversion(int number)
        {
            string binary = Convert.ToString(number, 2);
            string octal = Convert.ToString(number, 8);
            string hexa = Convert.ToString(number, 16);

            return "Decimal number : " + number + " binary is " + binary + ", octal is " + octal + " and hexa is " + hexa;
        }

client---

         ServiceReference1.WebService1SoapClient obj = new ServiceReference1.WebService1SoapClient();
            int num = Convert.ToInt32(TextBox1.Text);
            String res = obj.Conversion(num);
            Label2.Text = res;