我正在使用Entity Framework 6并且我一直收到以下错误:
违反PRIMARY KEY约束' PK_AssignmentType'。无法在对象' dbo.AssignmentType'。
中插入重复键
如您所见,我尝试将实体AssignmentType
的状态更改为unchanged
。当我为实体Assignment
分配AssignmentType
的外键然后将导航属性AssignmentType
设置为null时,我仍然得到相同的错误(在Assignments
的foreach循环中,而不是Comments
foreach循环。)
实体框架在哪里跟踪实体AssignmentType
,为什么它仍然认为它是一个新实体而不是现有实体?
实体Reporting
和Assignment
之间存在多对多关系。
[Route("")]
[HttpPost]
public IHttpActionResult Add(ReportingDTO data)
{
Reporting reporting = new Reporting { ID = Guid.NewGuid(), Date = DateTime.Now };
foreach (Assignment assignment in data.Assignments)
{
_db.Entry(assignment.AssignmentType).State = EntityState.Unchanged;
if (assignment.Reporting.Count > 0)
{
_db.Entry(assignment).State = EntityState.Added;
_db.Entry(assignment).State = EntityState.Modified;
}
reporting.Assignment.Add(assignment);
}
foreach (Comment comment in data.Comments)
{
comment.ID = Guid.NewGuid();
comment.AssignmentID = comment.Assignment.ID;
comment.Assignment = null;
comment.ReportingID= reporting.ID;
}
using(var transaction = _db.Database.BeginTransaction())
{
_db.Reporting.Add(reporting);
_db.Comments.AddRange(data.Comments);
_db.SaveChanges();
transaction.Commit();
}
return Ok(reporting);
}
Reporting.cs
[Table("Reporting")]
public partial class Reporting
{
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
public Reporting()
{
Assignment= new HashSet<Assignment>();
}
[Key]
public Guid ID{ get; set; }
[Column(TypeName = "date")]
public DateTime Date{ get; set; }
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
public virtual ICollection<Assignment> Assignment{ get; set; }
}
Assignment.cs
[Table("Assignment")]
public partial class Assignment
{
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
public Assignment()
{
Reporting = new HashSet<Reporting>();
}
[Key]
public Guid OID { get; set; }
[Required]
[StringLength(100)]
public string Name { get; set; }
public Guid AssignmentTypeID { get; set; }
[Required]
[StringLength(100)]
public string Project { get; set; }
public bool Completed { get; set; }
[ForeignKey("AssignmentTypeID")]
public virtual AssignmentType AssignmentType { get; set; }
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
public virtual ICollection<Reporting> Reporting { get; set; }
}
AssignmentType
[Table("AssignmentType")]
public partial class AssignmentType
{
[Key]
public Guid ID { get; set; }
[Required]
[StringLength(100)]
public string Name { get; set; }
}
答案 0 :(得分:1)
尝试这样的事情:
public IHttpActionResult Add(ReportingDTO data)
{
Reporting reporting = new Reporting { ID = Guid.NewGuid(), Date = DateTime.Now };
foreach (Assignment assignment in data.Assignments)
{
if (assignment.ID != null)
{
_db.Assignments.Attach(assignment);
_db.Entry(assignment).State = EntityState.Modified;
}
else
{
assignment.ID = Guid.NewGuid();
}
if (assignment.AssignmentType != null)
{
assignment.AssignmentTypeID = assignment.AssignmentType.ID;
assignment.AssignmentType = null;
}
}
reporting.Assignment.AddRange(data.Assignments);
foreach (Comment comment in data.Comments)
{
comment.ID = Guid.NewGuid();
comment.AssignmentID = comment.Assignment.ID;
comment.Assignment = null;
comment.ReportingID = reporting.ID;
}
_db.Reporting.Add(reporting);
_db.Comments.AddRange(data.Comments);
_db.SaveChanges();
return Ok(reporting);
}
除非您要更新实体,否则所有Entry()
操作在您的上下文中都是无用的。在这种情况下,在更新其状态之前,您必须Attach()
更新的实体。
另外,要回答您的初始问题:EF添加了新的AssignmentType,因为它丢失了现有的AssignmentType。每次请求命中时都会构建Controller,因此每次都会构建DbContext。当您创建新的DbContext时,它不知道以前的操作,例如返回Assignment
或其他任何操作(如果在查询期间指定AsNoTracking()
也是如此)。换句话说,如果DbContext没有跟踪实体,那么EF将尝试添加它
为了防止这种情况,您可以(并且确实应该)使用外键而不是导航属性。或者你可以Attach()
每个已知的实体(但如果你有外键它就没用了)。对于ManyToMany关系,您必须在添加/更新新实体之前查询数据库,否则,您将拥有双倍的关系。
或者,您也可以使用我称之为“链接表”的内容。它只是一个介于两个主要类之间的类。 EF已经为您的所有ManyToMany关系(检查您的数据库)执行此操作。基本上,它类似于:
public class A
{
public int Id {get; set;}
public virtual List<AB> ABs { get; set; }
}
public class B
{
public int Id {get; set;}
public virtual List<AB> BAs {get; set; }
}
public class AB
{
public int AId {get;set;}
public virtual A {get; set;}
public int BId {get;set;}
public virtual B {get; set;}
}
通过这种方式,您可以使用_db.ABs.Add(new AB{AId = 1, BId = 2})
添加新的AB(或删除一个),而无需处理其余的事情。