#region USER SECTION
        private void LoadUsers()
        {
            gridUsers.Visibility = Visibility.Visible;
        }

        private void AddForm(object sender, RoutedEventArgs e)
        {
            addUser.Visibility = Visibility.Visible;
            UserId.Text = "0";
            txtUserName.Text = "";
            txtUserNameOnBill.Text = "";
            txtUserUsername.Text = "";
            txtUserPassword.Password = "";
            txtUserPasswordPin.Password = "";
            cmbUserUserGroup.SelectedValue = 0;
            btnUserActive.IsDefault = false;
            btnUserWaiter.IsDefault = false;
        }

        /// <summary>
        /// Promjena vrijednosti na button-u "Active"
        /// </summary>
        public void btnActiveClick(object sender, RoutedEventArgs e)
        {
            btnUserActive.IsDefault = !btnUserActive.IsDefault;
        }

        /// <summary>
        /// Promjena vrijednosti na button-u "Waiter"
        /// </summary>
        public void btnWaiterClick(object sender, RoutedEventArgs e)
        {
            btnUserWaiter.IsDefault = !btnUserWaiter.IsDefault;
        }

        /// <summary>
        /// Zatvaranje forme za dodavanje korisnika
        /// </summary>
        public void CloseAddUserFormClick(object sender, RoutedEventArgs e)
        {
            addUser.Visibility = Visibility.Collapsed;
        }

        private void SaveUser(object sender, RoutedEventArgs e)
        {
            UserDM user = new UserDM();
            bool isValidated = true;

            //validacija
            if (txtUserName.Text == null || txtUserName.Text == String.Empty)
                isValidated = false;

            if (cmbUserUserGroup.SelectedValue.ToString() == String.Empty)
                isValidated = false;

            if (!isValidated)
                return;

            user.UserID = Convert.ToInt32(UserId.Text);
            user.Name = txtUserName.Text;
            user.NameOnBill = txtUserNameOnBill.Text;
            user.Username = txtUserUsername.Text;
            user.Password = Hash.GetHash(txtUserPassword.Password, Hash.HashType.SHA512);
            user.PasswordPIN = Hash.GetHash(txtUserPasswordPin.Password, Hash.HashType.SHA512);
            user.UserGroupID = Convert.ToInt32(cmbUserUserGroup.SelectedValue.ToString());
            user.Active = !btnUserActive.IsDefault;
            user.Waiter = !btnUserWaiter.IsDefault;

            if (UserId != null && Convert.ToInt32(UserId.Text) != 0)
                UsersCommunication.Update(user);
            else
                UsersCommunication.Insert(user);

            addUser.Visibility = Visibility.Collapsed;
            dgvUsers.ItemsSource = UsersCommunication.UsersGetAll();
        }

        private void EditForm(object sender, RoutedEventArgs e)
        {
            addUser.Visibility = Visibility.Visible;

            //setovanje vrijednosti za edit
            if (dgvUsers.SelectedValue != null && dgvUsers.SelectedValue.ToString() != String.Empty)
            {
                UserDM user = UsersCommunication.UsersGetById(Convert.ToInt32(dgvUsers.SelectedValue.ToString()));
                UserId.Text = user.UserID.ToString();
                txtUserName.Text = user.Name;
                txtUserNameOnBill.Text = user.NameOnBill;
                txtUserUsername.Text = user.Username;
                txtUserPassword.Password = "";
                txtUserPasswordPin.Password = "";
                cmbUserUserGroup.SelectedValue = user.UserGroupID;
                btnUserActive.IsDefault = !user.Active;
                btnUserWaiter.IsDefault = user.Waiter == null ? false : !user.Waiter.Value;
            }
        }

        private void DeleteUser(object sender, RoutedEventArgs e)
        {
            if (dgvUsers.SelectedValue == null || dgvUsers.SelectedValue.ToString() == String.Empty)
                return;

            UsersCommunication.Delete(Convert.ToInt32(dgvUsers.SelectedValue.ToString()));
            dgvUsers.ItemsSource = UsersCommunication.UsersGetAll();
        }
        #endregion