NHibernate在查询中使用错误的键，抛出ObjectNotFoundByUniqueKeyException

问题描述

使用NHibernate 5.2，由于执行以下操作时使用无效的密钥执行了错误的查询，因此我得到了ObjectNotFoundByUniqueKeyException：

var session = sessionFactory.OpenSession();

var employee = new Employee(){
    UserId = "joe",Certifications = new List<Certification>()
};

employee.Certifications.Add(new Certification() { Employee = employee});

var id = session.Save(employee);
session.Flush();
session.Clear();
var emp = session.Get<Employee>(id);

foreach(var e in emp.Certifications)
{
    Console.WriteLine(e.Id);
}

已执行查询

NHibernate: INSERT INTO Employee (UserId) VALUES (@p0); select SCOPE_IDENTITY();@p0 = 'joe' [Type: String (4000:0:0)]
NHibernate: INSERT INTO Certification (UserId) VALUES (@p0); select SCOPE_IDENTITY();@p0 = 'joe' [Type: String (4000:0:0)]
NHibernate: SELECT userquery_0_.Id as id1_0_0_,userquery_0_.UserId as userid2_0_0_ FROM Employee userquery_0_ WHERE userquery_0_.Id=@p0;@p0 = 1 [Type: Int32 (0:0:0)]
NHibernate: SELECT certificat0_.UserId as userid2_1_1_,certificat0_.Id as id1_1_1_,certificat0_.Id as id1_1_0_,certificat0_.UserId as userid2_1_0_ FROM Certification certificat0_ WHERE certificat0_.UserId=@p0;@p0 = 1 [Type: Int32 (0:0:0)]
NHibernate: SELECT userquery_0_.Id as id1_0_0_,userquery_0_.UserId as userid2_0_0_ FROM Employee userquery_0_ WHERE userquery_0_.UserId=@p0;@p0 = '1' [Type: String (4000:0:0)]

我期望在最后两个查询中使用@p0 = 'joe'，而不是1和'1'。谁能看到下面的映射问题来解释这种现象？

类/映射

public class Employee
{
    public virtual int Id { get; set; }
    public virtual string UserId { get; set; }
    public virtual ICollection<Certification> Certifications { get; set; }
}

public class EmployeeMap : ClassMap<Employee>
{
    public EmployeeMap()
    {
        Table("Employee");
        Id(x => x.Id);
        Map(x => x.UserId);
        HasMany(x => x.Certifications)
            .KeyColumn("UserId")
            .Cascade.All();
    }
}

public class Certification
{
    public virtual int Id { get; set; }
    public virtual Employee Employee { get; set; }
}

public class CertificationMap : ClassMap<Certification>
{
    public CertificationMap()
    {
        Table("Certification");
        Id(x => x.Id);
        References(x => x.Employee)
            .Column("UserId")
            .PropertyRef(x => x.UserId);
    }
}

解决方法

使用雇员的主键不收集，而是另一个属性-PropertyRef。而且我们必须告知一对多映射以及进行多对一映射

    HasMany(x => x.Certifications)
        .KeyColumn("UserId")
        .Cascade.All()
        // use property,not the ID,when searching for my items
       .PropertyRef("UserId")
       ;

事实上，缺少此映射，导致在NHibernate加载集合时使用ID（魔术1）