实体框架表示更新实体时属性为空

我正在尝试向现有集合添加一个新实体。但是，当这样做时，父实体会抱怨其他导航属性为空（尽管不是）。

I'm trying to add a new entity to an existing collection. But when doing so the 'parent' entity complains the other navigational properties are null (although they aren't).

错误：

类型为
'System.Data.Entity.Validation.DbEntityValidationException'的异常在Ela.Facade.dll中发生
，但未在用户代码中处理

An exception of type 'System.Data.Entity.Validation.DbEntityValidationException' occurred in Ela.Facade.dll but was not handled in user code

附加信息：一个或多个实体的验证失败。
有关详情，请参阅EntityValidationErrors属性。

Additional information: Validation failed for one or more entities. See 'EntityValidationErrors' property for more details.

基金状态：修改

错误：需要字段所有者

调试字段时所有者已正确加载：

When debugging the field Owner is loaded correctly:

基金类：

public class Fund
{
    public int FundId { get; set; }

    [Required]
    [Index("IDX_FundName", 2, IsUnique = true)]
    [MaxLength(25)]
    public string Name { get; set; }

    [Required]
    [Index("IDX_FundIdentifier", 2, IsUnique = true)]
    [MaxLength(25)]
    public string Identifier { get; set; }

    public double Balance { get; set; }

    [Required]
    [Index("IDX_FundName", 1, IsUnique = true)]
    [Index("IDX_FundIdentifier", 1, IsUnique = true)]
    public virtual ApplicationUser Owner { get; set; }

    public virtual ICollection<Transaction> Transactions { get; set; }

    public Fund()
    {
        Transactions = new List<Transaction>();
    }
}

CreateTransaction方法：

CreateTransaction method:

public Transaction CreateTransaction(Transaction newTransaction)
{
    var context = new ApplicationDbContext();
    try
    {
        var fund = context.Funds.FirstOrDefault(f => f.FundId == newTransaction.ToFund.FundId);
        newTransaction.ToFund = fund;
        fund.Transactions.Add(newTransaction);
        context.SaveChanges();
    }
    catch (DbEntityValidationException e)
    {
        foreach (var eve in e.EntityValidationErrors)
        {
            Console.WriteLine("Entity of type \"{0}\" in state \"{1}\" has the following validation errors:",
                eve.Entry.Entity.GetType().Name, eve.Entry.State);
            foreach (var ve in eve.ValidationErrors)
            {
                Console.WriteLine("- Property: \"{0}\", Error: \"{1}\"",
                    ve.PropertyName, ve.ErrorMessage);
            }
        }
        throw;
    }
    return context.Transactions.FirstOrDefault();
}

任何帮助或建议不胜感激！

Any help or recommendations are appreciated!