private async void ChangeLibrarianDataButton_Click(object sender, EventArgs e)
        {
            ChangeLibrarianDataButton.Enabled = false;
            if (LibrarianNameTB.Text == "" || LibrarianSurnameTB.Text == "" || LibrarianAddressTB.Text == "" || LibrarianEmailTB.Text == "" || LibrarianPhoneTB.Text == "")
            {
                MessageBox.Show("Izpolnite vsa polja.");
                return;
            }

            if (LibrarianNewPassTB.Text == "")
            {
                MessageBox.Show("Vpišite geslo.");
                return;
            }

            if (LibrarianNewPassTB.Text != LibrarianPassChkTB.Text)
            {
                MessageBox.Show("Gesli se ne ujemata.");
                return;
            }

            MessageBox.Show("Zapomnite si geslo!", "Opozorilo!");

            var u = new Librarian()
            {
                Name     = LibrarianNameTB.Text,
                Surname  = LibrarianSurnameTB.Text,
                Address  = LibrarianAddressTB.Text,
                Phone    = LibrarianPhoneTB.Text,
                Email    = LibrarianEmailTB.Text,
                Password = Helper.CreateMD5(LibrarianNewPassTB.Text)
            };

            if (await DatabaseManager.AddLibrarian(u))
            {
                MessageBox.Show("Registracija uspešna.");

                new LoginForm().Show();
                Dispose();
            }

            MessageBox.Show("Napaka pri registraciji.");
        }