c#-HasRequired和WithOptional不生成一对一关系

我有两个非常简单的对象：

public class GenericObject
{
    public int Id { get; set; }
    public string description { get; set; }
    public User UserWhoGeneratedThisObject { get; set; }
}

public class User
{
    public int Id { get; set; }  
    public string Name { get; set; }
    public string Lastname { get; set; }
}

我重写OnModelCreating函数来声明对象的关系：

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<GenericObject>().HasRequired(u => u.UserWhoGeneratedThisObject)
                                   .WithOptional();
    }

然后,在我的应用程序中,执行以下操作：

using (var ctx = new TestContext())
{
    GenericObject myObject = new GenericObject();
    myObject.description = "testobjectdescription";
    User usr = new User() { Name = "Test"};
    ctx.Users.Add(usr);
    //myObject.UserWhoGeneratedThisObject = usr;
    ctx.GenericObjects.Add(myObject);
    ctx.SaveChanges();
}

将myObject添加到数据库时,由于我没有分配User对象,是否应该在发生异常时？ (注释行)在这种情况下,我希望看到一个异常,但是代码可以正常工作.更糟糕的是,如果我在ctx.SaveChanges()之后添加以下两行：

var u = ctx.GenericObjects.Find(1);
System.Console.WriteLine(u.ToString());

我看到,尽管我没有将用户分配给GenericObject,但变量u实际上是GenericObjects指向我在数据库中创建的用户.

解决方法:

您应该阅读：Difference between .WithMany() and .WithOptional()?

编码：

using (var ctx = new Tests6Context()) {
    GenericObject myObject = new GenericObject();
    myObject.description = "testobjectdescription";
    User usr = new User() { Name = "Test" };
    ctx.Users.Add(usr);
    //myObject.UserWhoGeneratedThisObject = usr;
    ctx.GenericObjects.Add(myObject);


    myObject = new GenericObject();
    myObject.description = "testobjectdescription 2";
    usr = new User() { Name = "Test 2" };
    ctx.Users.Add(usr);
    //myObject.UserWhoGeneratedThisObject = usr;
    ctx.GenericObjects.Add(myObject);

    ctx.SaveChanges();
}

抛出：

System.Data.Entity.Infrastructure.DbUpdateException: Unable to determine the principal end of the ‘ef6tests.GenericObject_UserWhoGeneratedThisObject’ relationship. Multiple added entities may have the same primary key.

在简单的情况下,一个新用户和一个新GenericObject EF可以推断处于相同状态的两个实体之间可能的唯一关系.在其他情况下,他会抛出.

标签：fluent,entity-framework-6,visual-studio-2017,c,entity-framework
来源： https://codeday.me/bug/20191211/2105703.html