private void CreateThemeButton_Click(object sender, RoutedEventArgs e) { if (ThemeName.Text != "") { string themeName = ThemeName.Text; string answer = client.AddTheme(subjectId, themeName); if (answer == "succesfull") { main.Content = new AdminThemes(client, mw, main, subjectId); } } else { MessageBox.Show("Please enter subject name!"); } }