internal void CreateBook(string firstName, string lastName, string title, string isbn)
 {
     try
     {
         bookservice.CreateAndAddBook(firstName, lastName, title, isbn);
         bookDetails.Close();
         bookDetails.Clear();
         LoadAllBooks();
     }
     catch (ValidationException valEx)
     {
         MessageBox.Show(valEx.Message, "Error!",
                         MessageBoxButtons.OK, MessageBoxIcon.Error);
     }
 }