private void Button_Add_Click(object sender, RoutedEventArgs e) { if (string.IsNullOrEmpty(UrlInput)) { TextBox_UrlInput.Focus(); return; } if (DownloadTaskCollection.Any(x => x.Url == UrlInput)) { TextBox_UrlInput.Focus(); return; } addUserInputToTaskList(UrlInput); UrlInput = string.Empty; TextBox_UrlInput.Focus(); }