Question

我在设置实体中的表之间的关系方面遇到了一个小问题。基本上我有三个模型：AppUser，Assignment和CompletedAssignment。

public class AppUser
{
    [Display(Name = "Your Id:")]
    public int ID { get; set; }
    [Display(Name = "First Name")]
    public string FirstName { get; set; }
    [Display(Name = "Last Name")]
    public string LastName { get; set; }

    public virtual ICollection<CompletedAssignment> CompletedAssignments { get; set; }
}

public class Assignment
{   
    [Display(Name="Assignment ID")]
    public int ID { get; set; }
    [Display(Name = "Assignment Name")]
    public string AssignmentName { get; set; }
    [Display(Name = "Assignment Description")]
    [DataType(DataType.MultilineText)]
    public string Description { get; set; } 
    public DateTime CreationDate { get; set; }

    public Assignment(){
        this.CreationDate = DateTime.Now;
    }

    public virtual ICollection<CompletedAssignment> Assignments { get; set; }
}

public class CompletedAssignment
{
    public int ID { get; set; }
    [Display(Name = "Assignment ID")]
    public int AssignmentID { get; set; }
    [Display(Name = "Student ID")]
    public int AppUserID { get; set; }
    public DateTime CompletionDate{get;set;}

    public CompletedAssignment()
    {
        this.CompletionDate = DateTime.Now;
    }

    public virtual Assignment Assignment { get; set; }
    public virtual AppUser AppUser { get; set; }
}

我（想）我在它们之间配置了一组关系：AppUser和CompletedAssignment之间的一对多关系，以及Assignment和CompletedAssignment之间的一对多关系所以我在CompletedAssignment表中有两个外键。

当我尝试使用用户提供的两个外键ID向数据库添加新CompletedAssignment时，会出现问题。

错误消息：

＆＃34; INSERT语句与FOREIGN KEY约束冲突 \＆＃34; FK_dbo.CompletedAssignments_dbo.AppUsers_AppUserID \＆＃34 ;.冲突发生在数据库\＆＃34; aspnet-name-20160527092700 \＆＃34;，表中 \＆＃34; dbo.AppUsers \＆＃34;，列＆＃39; ID＆＃39;。\ r \ n该声明已被终止。＆＃34;

导致它的代码：

[HttpPost]
public ActionResult Create([Bind(Include = "ID,AssignmentID,UserID,CompletionDate")] CompletedAssignment completedAssignment)
{
    if (ModelState.IsValid)
    {
        db.CompletedAssignments.Add(completedAssignment);

        db.SaveChanges();

        return RedirectToAction("Index");
    }

    return View(completedAssignment);
}

到目前为止，我从SQL中记得这个错误意味着已经为查询提供了不存在的密钥，但我已经检查了几次，并且两个表中都提供了密钥。我有点努力去理解实体数据库交互实际上是如何工作的，所以任何形式的帮助都会受到赞赏:)

Answer 1

AppUserID没有价值。

你写了

[Bind(Include = "ID,AssignmentID,UserID,CompletionDate")]

应该是

[Bind(Include = "ID,AssignmentID,AppUserID,CompletionDate")]

向具有许多外键的表添加新行

1 个答案: