相同的键值已经被跟踪

Question

相同的键值已经被跟踪

6

System.InvalidOperationException: The instance of entity type 'ProjectAssignment' cannot be tracked because another instance with the same key value for {'ProjectID'} is already being tracked. When attaching existing entities, ensure that only one entity instance with a given key value is attached. Consider using 'DbContextOptionsBuilder.EnableSensitiveDataLogging' to see the conflicting key values.
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.IdentityMap`1.Add(TKey key, InternalEntityEntry entry)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.St

我使用Worker（ID和其他列）和Project（ID和其他列）实体以及ProjectAssignment（多个Project ID对应多个Workers）交叉绑定创建了一个项目。但是，当我尝试获取ProjectAssignment数据时，在Application Insights中出现错误。奇怪的是之前没有显示id。

这里是链接：https://github.com/Streamc/ContosoObserve1/tree/master/Proj_s

 context.Database.EnsureCreated();

  var ProjectAssignments = new ProjectAssignment[]
             {
                    new ProjectAssignment
                    {
                        ProjectID = Projects.Single( i => i.ID == 1).ID,
                        WorkerID = Workers.Single( i => i.ID == 1).ID,
                    },
                     new ProjectAssignment
                    {
                        ProjectID = Projects.Single( i => i.ID == 1).ID,
                        WorkerID = Workers.Single( i => i.ID == 2).ID,
                    },
                     new ProjectAssignment
                    {
                        ProjectID = Projects.Single( i => i.ID == 1).ID,
                        WorkerID = Workers.Single( i => i.ID == 3).ID,
                    },
                    new ProjectAssignment
                    {
                        ProjectID = Projects.Single( i => i.ID == 2).ID,
                        WorkerID = Workers.Single( i => i.ID == 1).ID,
                    },
                    new ProjectAssignment
                    {
                        ProjectID = Projects.Single( i => i.ID == 3).ID,
                        WorkerID = Workers.Single( i => i.ID == 1).ID,
                    },
                    new ProjectAssignment
                    {
                        ProjectID = Projects.Single( i => i.ID == 4).ID,
                        WorkerID = Workers.Single( i => i.ID == 1).ID,
                    },
                    new ProjectAssignment
                    {
                        ProjectID = Projects.Single( i => i.ID == 2).ID,
                        WorkerID = Workers.Single( i => i.ID == 2).ID,
                    },
                    new ProjectAssignment
                    {
                        ProjectID = Projects.Single( i => i.ID == 2).ID,
                        WorkerID = Workers.Single( i => i.ID == 3).ID,
                    },
                    new ProjectAssignment
                    {
                        ProjectID = Projects.Single( i => i.ID == 2).ID,
                        WorkerID = Workers.Single( i => i.ID == 4).ID,
                    }

             };
            foreach (ProjectAssignment ss in ProjectAssignments)
            {
                context.ProjectAssignments.Add(ss);
            }
            context.SaveChanges();



 public class ProjectAssignment
    {
        [Key]
        public int ProjectID { get; set; }
        public int WorkerID { get; set; }


        public Project Project { get; set; }
        public Worker Worker { get; set; }

    }
   public class Worker
    {
        public int ID { get; set; }
        public string Firstname { get; set; }
        public string Lastname { get; set; }
        public string Fathername { get; set; }
        public string email { get; set; }    
        public string Company_name { get; set; }
        public ICollection<ProjectAssignment> ProjectAssignment { get; set; }

    }
    public class Project
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public string Customer_Company { get; set; }
        public string Executive_Company { get; set; }
        public int ManagerID { get; set; }    
        public int WorkerID { get; set; }    
        public DateTime Begin_date { get; set; }
        public DateTime End_date { get; set; }
        public int Priority { get; set; }    
        public string Test_comment { get; set; }    
        public ICollection<ProjectAssignment> ProjectAssignment { get; set; }
    }

- streamc

2

请提供一些能够重现此错误的代码。请参考[mcve]以获取创建良好代码示例的提示。 - Code-Apprentice

1个回答

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可以查看英文原文，
原文链接

- Georg Patscheider · Accepted Answer

请仔细阅读错误信息：

实体类型 'ProjectAssignment' 的实例无法被跟踪，因为另一个实例已经使用相同的 {'ProjectID'} 键值进行跟踪。

因此，问题在于我们有两个或更多具有相同 ProjectID 的 ProjectAssignment。

如果我们查看代码，会发现我们将相同的 ProjectID 分配了两次：

 var ProjectAssignments = new ProjectAssignment[] {
     new ProjectAssignment {
         ProjectID = Projects.Single( i => i.ID == 1).ID, // ID == "1"
         WorkerID = Workers.Single( i => i.ID == 1).ID,
     },
     new ProjectAssignment {
         ProjectID = Projects.Single( i => i.ID == 1).ID, // ID == "1", again
         WorkerID = Workers.Single( i => i.ID == 2).ID,
     },
     // ...
 }

根本原因似乎是将 ProjectID 建模为主键而不是外键。主键必须是唯一的。您可能想要的是由ProjectID和WorkerID组成的复合主键。

查看您的 Github 项目中的 ProjectContext，这个复合主键已经存在：

modelBuilder.Entity<ProjectAssignment>().HasKey(c => new { c.ProjectID, c.WorkerID });

但它与ProjectAssignment.ProjectID上的[Key]注释冲突。移除此[Key]属性！