尽管据我所知我没有任何循环引用，但是我遇到了循环引用序列化错误。我正在从数据库中检索一组订单，并将它们作为JSON发送到客户端。所有代码如下所示。

这是错误：

错误

序列化类型为’System.Data.Entity.DynamicProxies.Order_83CECF2AA4DE38232F9077D4B26941AB96BC61230419EA8AC42C9100E6072812’的对象时，检测到循环引用。说明：执行当前Web请求期间发生未处理的异常。请查看堆栈跟踪，以获取有关错误及其在代码中起源的更多信息。

异常详细信息：System.InvalidOperationException：序列化类型为’System.Data.Entity.DynamicProxies.Order_83CECF2AA4DE38232F9077D4B26941AB96BC61230419EA8AC42C9100E6072812’的对象时，检测到循环引用。

源错误：

当前Web请求的执行期间生成了未处理的异常。可以使用下面的异常堆栈跟踪来标识有关异常的来源和位置的信息。

我的课程如下：

订购

public class Order
{
    [Key]
    public int OrderId { get; set; }

    public int PatientId { get; set; }
    public virtual Patient Patient { get; set; }

    public int CertificationPeriodId { get; set; }
    public virtual CertificationPeriod CertificationPeriod { get; set; }

    public int AgencyId { get; set; }
    public virtual Agency Agency { get; set; }

    public int PrimaryDiagnosisId { get; set; }
    public virtual Diagnosis PrimaryDiagnosis { get; set; }

    public int ApprovalStatusId { get; set; }
    public virtual OrderApprovalStatus ApprovalStatus { get; set; }

    public int ApproverId { get; set; }
    public virtual User Approver { get; set; }

    public int SubmitterId { get; set; }
    public virtual User Submitter { get; set; }

    public DateTime ApprovalDate { get; set; }

    public DateTime SubmittedDate { get; set; }
    public Boolean IsDeprecated { get; set; }
}

患者

public class Patient
{
    [Key]
    public int PatientId { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string MiddleInitial { get; set; }
    public bool IsMale;
    public DateTime DateOfBirth { get; set; }

    public int PatientAddressId { get; set; }
    public Address PatientAddress { get; set; }

    public bool IsDeprecated { get; set; }
}

认证期限

public class CertificationPeriod
{
    [Key]
    public int CertificationPeriodId { get; set; }
    public DateTime startDate { get; set; }
    public DateTime endDate { get; set; }
    public bool isDeprecated { get; set; }
}

机构

public class Agency
{
    [Key]
    public int AgencyId { get; set; }
    public string Name { get; set; }

    public int PatientAddressId { get; set; }
    public virtual Address Address { get; set; }
}

诊断

public class Diagnosis
{
    [Key]
    public int DiagnosisId { get; set; }
    public string Icd9Code { get; set; }
    public string Description { get; set; }
    public DateTime DateOfDiagnosis { get; set; }
    public string Onset { get; set; }
    public string Details { get; set; }
}

OrderApprovalStatus

public class OrderApprovalStatus
{
    [Key]
    public int OrderApprovalStatusId { get; set; }
    public string Status { get; set; }
}

用户

public class User
{
    [Key]
    public int UserId { get; set; }
    public string Login { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string NPI { get; set; }
    public string Email { get; set; }

}

注意：地址类别是编辑过程中的新添加

地址

public class Address
{
    [Key]
    public int AddressId { get; set; }
    public string StreetAddress { get; set; }
    public string City { get; set; }
    public string State { get; set; }
    public string Zip { get; set; }
    public string Phone { get; set; }
    public string Title { get; set; }
    public string Label { get; set; }
}

执行序列化的代码在这里：

摘自OrderController

    public ActionResult GetAll()
    {
        return Json(ppEFContext.Orders, JsonRequestBehavior.AllowGet);
    }

谢谢