如何使用lambda从书桌中选择日期？

Question

我有以下功能：

var filtered_books = book_table.Where<Book>(d => d.CategoryID == Convert.ToInt32(drpCategory.SelectedItem.Value));
lstBooks.DataSource = filtered_books;
lstBooks.DataBind();

错误：An exception of type 'System.ArgumentNullException' occurred in System.Core.dll but was not handled in user code.