protected void Connection(object sender, EventArgs e)
    {
        string User = "";
        string Password = "";
        string Istanza = "";
        SqlConnection myConnection = null;
        try
        {
            User = LoginName1.Value;
            Password = Password1.Value;
            Istanza = DropDownIstance.SelectedItem.ToString();
            myConnection = new SqlConnection("user id="+User+";" +
                                       "password="+ Password + ";Data Source=" + Istanza + ";" +
                                       "Trusted_Connection=yes;" +
                                       "Database=main;" +
                                       "connection timeout=30");

            myConnection.Open();

                // Set up a command with the given query and associate
                // this with the current connection.
                using (SqlCommand cmd = new SqlCommand("SELECT name from sys.databases", myConnection))
                {
                    using (IDataReader dr = cmd.ExecuteReader())
                    {
                        while (dr.Read())
                        {
                            DropDownListDB.Items.Add(dr[0].ToString());
                        }
                    }
                }


        }
        catch (Exception Err)
        {
            string ErrorMessage = Err.Message;
        }
        finally
        {
            myConnection.Close();
        }
    }