Question

我正在关注本教程http://www.asp.net/web-api/overview/data/using-web-api-with-entity-framework/part-4

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Entity;
using System.Data.Entity.Infrastructure;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Threading.Tasks;
using System.Web.Http;
using System.Web.Http.Description;
using BookService.Models;

namespace BookService.Controllers
{
    public class BooksController : ApiController
    {
        private BookServiceContext db = new BookServiceContext();

        // GET: api/Books
        public IQueryable<Book> GetBooks()
        {
            return db.Books;
                    // new code:
                    .Include(b => b.Author);
        }

我说添加.Include(b => b.Author);来执行急切加载。并使用System.Data.Entity.Include 我已经这样做了，我还添加了Entityframwork和nuget，但我得到了

意外的令牌无法解决'包含' 代码无法访问

我仍然错过了Etityframwork.dll，如果是的话，我该怎么做？

Answer 1

如何阅读from related article of MSDN - Loading Related Entities

预先加载是查询一种类型实体的过程还会将相关实体作为查询的一部分加载。渴望加载通过使用Include方法实现。

using (var context = new BloggingContext()) 
{ 
    // Load all blogs and related posts 
    var blogs1 = context.Blogs 
                          .Include(b => b.Posts) 
                          .ToList(); 

    // Load one blogs and its related posts 
    var blog1 = context.Blogs 
                        .Where(b => b.Name == "ADO.NET Blog") 
                        .Include(b => b.Posts) 
                        .FirstOrDefault(); 

    // Load all blogs and related posts  
    // using a string to specify the relationship 
    var blogs2 = context.Blogs 
                          .Include("Posts") 
                          .ToList(); 

    // Load one blog and its related posts  
    // using a string to specify the relationship 
    var blog2 = context.Blogs 
                        .Where(b => b.Name == "ADO.NET Blog") 
                        .Include("Posts") 
                        .FirstOrDefault(); 
}

但你的代码有错字;你的;太多了：

return db.Books.Include(b => b.Author);

问题在于：

return db.Books; <---

不能使用。包括

1 个答案: