c# sql connect

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;
using System.Security.Cryptography;

namespace proba
{
    public partial class Form1 : Form
    {
        SqlConnection connection;
        string connectionString = "Server=U2PC07\\SQLEXPRESS; Database=steam; Integrated Security=SSPI;";
        SqlCommand command;
        SqlDataReader dataReader;
        string sql = "SELECT dbo.Game.name, dbo.[User].username FROM dbo.Game INNER JOIN dbo.Library ON dbo.Game.appID = dbo.Library.appID INNER JOIN dbo.[User] ON dbo.[User].idU = dbo.Library.idU";

        public Form1()
        {
            InitializeComponent();
            connection = new SqlConnection(connectionString);
        }

        private void button1_Click(object sender, EventArgs e)
        {
            try
            {
                connection.Open();
                command = new SqlCommand(sql, connection);
                dataReader = command.ExecuteReader();
                string bibl = "";
                while (dataReader.Read())
                    bibl += dataReader.GetValue(1) + " ima igricu " + dataReader.GetValue(0) + Environment.NewLine;

                MessageBox.Show(bibl);
                connection.Close();
            }
            catch (Exception error)
            {
                MessageBox.Show("Greska: " + error.ToString());
            }

        }


        private void log_Click(object sender, EventArgs e)
        {
            string password = passwd.Text;
            byte[] encodedPassword = new UTF8Encoding().GetBytes(password);
            byte[] hash = ((HashAlgorithm)CryptoConfig.CreateFromName("MD5")).ComputeHash(encodedPassword);
            string encoded = BitConverter.ToString(hash).Replace("-", string.Empty);
            MessageBox.Show(encoded);
        }
    }
}