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Accepted
Иван Иванов
Asked:2020-10-03 15:09:42 +0000 UTC2020-10-03 15:09:42 +0000 UTC

LINQ，通过 Id 填充嵌套对象

  • 772

我们有两个班级：

public class Book
{
    public int Id { get; set; }
    public BookCategory BookCategory { get; set; }
}

public class BookCategory
{
    public int Id { get; set; }
    public string Name { get; set; }
}

帮助按类别填写图书清单

var books = new List<Book>()
{
    new Book { Id = 1, BookCategory = new BookCategory { Id = 1 }  },
    new Book { Id = 2, BookCategory = new BookCategory { Id = 1 }  },
    new Book { Id = 3, BookCategory = new BookCategory { Id = 2 }  },
    new Book { Id = 4, BookCategory = new BookCategory { Id = 2 }  }
};
var categories = new List<BookCategory>
{
    new BookCategory { Id = 1, Name = "Первая категория" },
    new BookCategory { Id = 2, Name = "Вторая категория" }
};

List<Book> booksWithCategories = //linq;

更新：

我想获得一个包含 BookCategory.Name 的 Book 对象列表

c#

1 个回答

  1. Best Answer

    创建新书的选项：

      List<Book> booksWithCategories = books.Select(b => new Book()
  {
    BookCategory = categories.SingleOrDefault(c => c.Id == b.BookCategory.Id),
    Id = b.Id
  }).ToList();

    填写旧书的选项：

      books.ForEach(b => b.BookCategory = categories.SingleOrDefault(c => c.Id == b.BookCategory.Id));
  List<Book> booksWithCategories = books.ToList();
    • 3

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