如何通过IN从列表过滤中进行选择

Question

问：

我有一个像这样的对象列表：

List<object> entities = GetallEntities();

上一个列表中的第一个对象是：List<Books>。

现在我想获得所有id

的书籍

存在于以下列表中：

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

Answer 1

假设您的Books类具有Id属性，并且一个实例代表一本书：

// 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; }
}

...

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));