protected void register_Click(object sender, EventArgs e)
 {
     if (Page.IsValid)
     {
         try
         {
             string encrypted = FormsAuthentication.HashPasswordForStoringInConfigFile(password.Text, "SHA1");
             BLayer myBlayer  = new BLayer();
             User   myUser    = new User();
             myUser.username    = username.Text;
             myUser.password    = encrypted;
             myUser.userOnoma   = fname.Text;
             myUser.userRank    = rank.Text;
             myUser.userEponymo = lname.Text;
             myUser.userMonada  = monada.Text;
             int value = myBlayer.register(myUser);
             if (value == -1)
             {
                 error.Text = "Το όνομα χρήστη που εισάγατε χρησιμοποιείται ήδη. Παρακαλώ εισάγετε ένα διαφορετικό.";
             }
             else
             {
                 Response.Redirect("../login.aspx");
             }
         }
         catch (Exception ex)
         {
             error.Text = ex.Message.ToString();
         }
     }
 }