private void searchTxb_TextChanged(object sender, TextChangedEventArgs e)
{
if (searchTxb.Text == "")
{
dsBookCat = bookCatalog.GetBookInfo();
this.DataContext = dsBookCat.Tables["Category"];
}
else
{
dsBookCat = bookCatalog.SearchBook(searchTxb.Text);
this.DataContext = dsBookCat.Tables["Category"];
}
}