private async void SearchVisitor()
{
LBVisitorItemList.DataContext = null;
GridVisitorItemDetails.DataContext = null;
ComboBoxItem typeItem2 = (ComboBoxItem)CBVisitorSearchType.SelectedItem;
string value = typeItem2.Content.ToString();
var searchvalue = TBVisitorSearchValue.Text.Equals("") ? "0" : TBVisitorSearchValue.Text;
BookProcessor book = new BookProcessor();
VisitorItem = await book.GetVisitorBooks(value, searchvalue);
LBVisitorItemList.DataContext = VisitorItem;
}