Question

好的，我在ApplicationUser和QuestionResults之间有一个关系，我的模型如下，userId和UserName被检索，但我真的需要在QuestionResults实体上将UserId设置为foreignKey。

非常感谢任何帮助我收到的错误如下：

An exception of type 'System.NullReferenceException' occurred in STRA.dll but was not handled in user code

Additional information: Object reference not set to an instance of an object.
on these lines of code:

qr.User.Id = User.Identity.GetUserId();
qr.User.UserName = User.Identity.GetUserName();

模型

public class QuestionResult
    {
        public QuestionResult()
        {
            DateCreated = DateTime.Now;
            DateModified = DateTime.Now;
        }
        public int Id { get; set; }
        public DateTime? DateCreated { get; set; }
        public DateTime? DateModified { get; set; }
        public int QuestionScore { get; set; }
        //navigation properties
        public virtual ApplicationUser User { get; set; }
        //public ICollection<CategoryResult> CategoryResult { get; set; }
        //public virtual Category Category { get; set; }
        [NotMapped]
        public int CategoryId { get; set; }
        public virtual Question Question { get; set; }
        public int QuestionId { get; set; }
        //public virtual Category Category { get; set; }
        //public int CategoryId { get; set; }
    }
public class ApplicationUser : IdentityUser
    {
        public string FirstName { get; set; }
        public string Surname { get; set; }
        public string Industry { get; set; }
        public string GlobalRegion { get; set; }
        public string CurrentSituation { get; set; }
        public int SalesForceSize { get; set; }
        public bool IsVerified { get; set; }
        //navigation properties
        public virtual ICollection<CategoryResult> CategoryResult { get; set; }
        public virtual ICollection<QuestionResult> QuestionResult { get; set; }
        //public virtual ICollection<Report> Report { get; set; }
        //public virtual ICollection<SurveyResult> SurveyResult { get; set; }
        public virtual Organisation Organisation { get; set; }
        public int? OrganisationId { get; set; }

        public async Task<ClaimsIdentity> GenerateUserIdentityAsync(UserManager<ApplicationUser> manager)
        {
            // Note the authenticationType must match the one defined in CookieAuthenticationOptions.AuthenticationType
            var userIdentity = await manager.CreateIdentityAsync(this, DefaultAuthenticationTypes.ApplicationCookie);
            // Add custom user claims here
            return userIdentity;
        }

    }

Answer 1

您的代码与此::

等效

ShopId

如果var user = qr.User; user.Id = User.Identity.GetUserId();已经与QuestionResult相关联，那么您不会更改哪个User与User相关联，那么您将更改QuestionResult现有的Id - 并且无论如何都不允许这样做。

但User尚未与QuestionResult相关联。 User为空 - 因此您将获得空引用异常。

通常，如果将外键添加到模型中，实体框架中的生命会更容易：

qr.User

现在您可以直接设置外键：

public class QuestionResult { public string UserId { get; set; } public virtual ApplicationUser User { get; set; } }

参考文献：

Why does Entity Framework Reinsert Existing Objects into My Database?

Making Do with Absent Foreign Keys

Answer 2

那么，你想为用户标识做出预测关键吗？

你可以这样做：

<api xmlns="http://ws.apache.org/ns/synapse" name="sample" context="/api/sample">
   <resource methods="OPTIONS GET" uri-template="/{val1}/groups/{val2}.json?q1={v1}&q2={v2}">
  <inSequence>
     <property name="uri.var.q1" expression="$url:q1"></property>
     <property name="uri.var.q2" expression="$url:q2"></property>
     <property name="uri.var.val1" expression="get-property('uri.var.val1')"></property>
     <property name="uri.var.val2" expression="get-property('uri.var.val2')"></property>
     <send>
        <endpoint>
           <http method="GET" uri-template=""></http>
        </endpoint>
     </send>
  </inSequence>
  <outSequence>
     <send></send>
  </outSequence>
  </resource>
</api>

出现此错误，因为您对模型或数据类有一些问题。

Answer 3

将其设为字符串

型号：

public ApplicationUser User { get; set; }
public string UserId { get; set; }

控制器：

qr.UserId = User.Identity.GetUserId();

工作得很完美，甚至创造了外键，这很容易。非常感谢！

使用User.Identity.GetUserId的ASP MVC应用程序用户空

3 个答案: