C# 请求特定数据将返回所有关联的实体,而不使用Include()
我正在创建一个简单的WebAPI(MVC),目前我正在使用实体框架代码优先的方法。我拥有以下实体: 作者、课程、机构 我已经建立了这样一种关系,一个作者可以有N个课程和N个机构。我正在API上编写以下方法:C# 请求特定数据将返回所有关联的实体,而不使用Include(),c#,entity-framework-6,C#,Entity Framework 6,我正在创建一个简单的WebAPI(MVC),目前我正在使用实体框架代码优先的方法。我拥有以下实体: 作者、课程、机构 我已经建立了这样一种关系,一个作者可以有N个课程和N个机构。我正在API上编写以下方法: public class PlutoController : ApiController { private readonly PlutoDbContext _context; public PlutoController() { _context
public class PlutoController : ApiController
{
private readonly PlutoDbContext _context;
public PlutoController()
{
_context = new PlutoDbContext();
}
[HttpGet]
public IHttpActionResult GetAuthors()
{
var authors = _context.Authors
.Where(a => a.AuthorID == 1).ToList();
return Ok(authors);
}
}
但是,调用api会返回作者及其相关课程和机构
[
{
"Courses": [
{
"CourseSections": [],
"Tags": [],
"CourseID": 1,
"AuthorID": 1,
"Title": "C# Advanced",
"Description": "C# Advanced Description",
"Price": 69,
"LevelString": "Advanced",
"Level": 3
},
{
"CourseSections": [],
"Tags": [],
"CourseID": 2,
"AuthorID": 1,
"Title": "C# Intermediate",
"Description": "C# Intermediate Description",
"Price": 49,
"LevelString": "Intermediate",
"Level": 2
},
{
"CourseSections": [],
"Tags": [],
"CourseID": 3,
"AuthorID": 1,
"Title": "Clean Code",
"Description": "Clean Code Description",
"Price": 99,
"LevelString": "Intermediate",
"Level": 2
}
],
"Institution": [
{
"InstitutionId": 1,
"AuthorId": 1,
"InstitutionName": "University of Windsor"
},
{
"InstitutionId": 2,
"AuthorId": 1,
"InstitutionName": "Boston University"
},
{
"InstitutionId": 4,
"AuthorId": 1,
"InstitutionName": "Arizona State University"
}
],
"AuthorID": 1,
"Name": "Bill Gates"
}]
在这方面,我可以看到,我们正在做一些渴望加载,这不是我想要的。我如何只获取作者的详细信息
以下是我生成的模型:
作者
您遇到的问题是懒散的加载(而不是急切的加载)。禁用它
public partial class YourDBContext : DbContext
{
public YourDBContext(): base("name=YourDBContext")
{
this.Configuration.LazyLoadingEnabled = false;
}
}
我猜在你的背景下是真的?这对我来说很有用!!谢谢:)但我不明白这是怎么回事。急切加载不意味着在一个查询中加载所有实体吗?急切加载意味着在加载主实体时加载相关实体。但是您需要使用Include()来实现这一点。在您的情况下,因为您不使用它,所以当您使用ToList()时,它不会加载相关的实体。但是,当您“返回”它时,序列化程序开始访问这些属性,EF开始加载这些属性。
namespace PlutoAPI.Models
{
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Data.Entity.Spatial;
public partial class Courses
{
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
public Courses()
{
CourseSections = new HashSet<CourseSections>();
Tags = new HashSet<Tags>();
}
[Key]
public int CourseID { get; set; }
public int AuthorID { get; set; }
[Required]
[StringLength(255)]
public string Title { get; set; }
[Required]
[StringLength(8000)]
public string Description { get; set; }
public short Price { get; set; }
[Required]
[StringLength(50)]
public string LevelString { get; set; }
public byte Level { get; set; }
public virtual Authors Authors { get; set; }
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
public virtual ICollection<CourseSections> CourseSections { get; set; }
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
public virtual ICollection<Tags> Tags { get; set; }
}
}
namespace PlutoAPI.Models
{
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Data.Entity.Spatial;
[Table("Institution")]
public partial class Institution
{
public int InstitutionId { get; set; }
public int? AuthorId { get; set; }
[Required]
[StringLength(50)]
public string InstitutionName { get; set; }
public virtual Authors Authors { get; set; }
}
}
public partial class YourDBContext : DbContext
{
public YourDBContext(): base("name=YourDBContext")
{
this.Configuration.LazyLoadingEnabled = false;
}
}