celsius

 server

public double convert(double cel)
        {
            return (cel * 9) / 5 + 32;
        }

client ------

            double c1 = Convert.ToDouble(TextBox1.Text);
            ServiceReference1.WebService1SoapClient obj = new ServiceReference1.WebService1SoapClient();
            double res = obj.convert(c1);
            Label2.Text = Convert.ToString(res);