如何從列表過濾通過

Question

Q選擇：

我有對象的列表如下：

List<object> entities = GetallEntities();

在前面的列表中的第一個對象是：List<Books>。

現在我想獲得這id

存在以下列表中的所有書籍：

List<string> BookIds = new List<string>();

Answer 1

假設你Books類有一個Id財產和一個實例代表一本書：

// Get the first element of your entity-list which is of type `List<Books>` 
List<Books> bookList = entities.OfType<List<Books>>().First(); 
List<string> BookIds = new List<string>(); 
// fill your id list here ... 

// filter your books by the list of ids 
IEnumerable<Books> filteredBooks = 
       bookList.Where(b => BookIds.Any(id => id == b.Id); 

Answer 2

public class Book 
{ 
    public string id { get; set; } 
} 

個

...

List<object> entities = new List<object> { new Book { id = "1" }, new Book { id = "2" } }; 
List<string> bookIds = new List<string> { "2" }; 

IEnumerable<object> books = entities.Where(e => e is Book && bookIds.Contains(((Book)e).id));