ADO.NET UpdateSalary (Procedures)

//alter procedure updateSalary
//    @id int,
//    @newSalary decimal(6,1),
//    @salary decimal(6,1) output
//as
//begin
//    update Users set @salary=salary+@newSalary, salary=salary+@newSalary where id=@id;
//end

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace UpdateSalary
{
    public partial class Form1 : Form
    {
        SqlConnection con;

        public Form1()
        {
            con = new SqlConnection(@"Server=VAKHO-PC; Database=TestDB; Integrated Security=true;");
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            SqlCommand updateCommand = new SqlCommand("dbo.updateSalary", con);
            updateCommand.CommandType = CommandType.StoredProcedure;

            SqlParameter id = new SqlParameter("@id", SqlDbType.Int);
            SqlParameter newSalary = new SqlParameter("@newSalary", SqlDbType.Decimal);
            SqlParameter salary = new SqlParameter("@salary", SqlDbType.Decimal);

            updateCommand.Parameters.Add(id).Value = Convert.ToDecimal(textBox1.Text);
            updateCommand.Parameters.Add(newSalary).Value = Convert.ToDecimal(textBox2.Text);
            updateCommand.Parameters.Add(salary).Direction = ParameterDirection.Output;

            try
            {
                con.Open();
                updateCommand.ExecuteNonQuery();
                MessageBox.Show(salary.Value.ToString(), "Updated Salary", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
            catch (SqlException ex)
            {
                MessageBox.Show(ex.Message, "Sql Error!", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            finally
            {
                con.Close();
            }
        }
    }
}