实体框架插入错误的数据

我有一段代码，我正在更新数据库中的一条记录，使用ValueInjector复制该对象，然后尝试使用Entity框架将该新对象添加到我的数据库中：

//Get record to update
File currentFile = db.Files.First(t => t.FileId == updatedFile.FileId && t.CustomerId == PrimaryUser);
currentFile.ToLanguage = 2; //update that record
File copy = Helpers.CopyFile(currentFile); //copy the currentFile
copy.FileId = Guid.NewGuid();
copy.ToLanguage = 3;
copy.Project = null;
db.Files.Add(copy); //add new record to the database
db.SaveChanges();

CopyFile的定义：

public static VerbalInk.Data.File CopyFile(Data.File source)
{
    Data.File newFile = new Data.File();
    newFile.InjectFrom(source);
    return newFile;
}

当我在db.Files.Add(copy);行放置断点，然后查看copy.ToLanguage时，它的预期值为3，但由于某种原因，当我将更改保存到数据库时，两条记录的ToLanguage的值都为2。

有人知道为什么会发生这种情况，以及我如何才能获得插入的ToLanguage的正确值吗？

更新：

我发现，如果我使用以下行禁用数据上下文的懒惰加载：

db.Configuration.LazyLoadingEnabled = false;

那么一切都会按预期更新。有人能解释为什么会发生这种情况吗？有没有一种方法可以让我的代码在不禁用懒惰加载的情况下工作？

File定义：

public partial class File
{
    public File()
    {
        this.FileServices = new HashSet<FileService>();
        this.FileAudioVariables = new HashSet<FileAudioVariable>();
        this.FileLanguages = new HashSet<FileLanguage>();
    }
    public System.Guid FileId { get; set; }
    public System.Guid CustomerId { get; set; }
    public Nullable<System.Guid> TemplateId { get; set; }
    public Nullable<System.Guid> OrderId { get; set; }
    public string FileName { get; set; }
    public bool IsMailInFile { get; set; }
    public string FileUrl { get; set; }
    public Nullable<int> NumberOfSpeakers { get; set; }
    public int AudioLength { get; set; }
    public int BillableMinutes { get; set; }
    public Nullable<int> StatusId { get; set; }
    public string Notes { get; set; }
    public string VirtualType { get; set; }
    public System.DateTime CreateDate { get; set; }
    public System.DateTime UploadDate { get; set; }
    public bool Tracked { get; set; }
    public bool Exported { get; set; }
    public Nullable<bool> IsConverting { get; set; }
    public Nullable<bool> IsInfected { get; set; }
    public Nullable<System.DateTime> OrderDate { get; set; }
    public Nullable<System.DateTime> StartDate { get; set; }
    public Nullable<System.DateTime> DueDate { get; set; }
    public Nullable<System.Guid> TranscriptionistId { get; set; }
    public string TranscriptionistNotes { get; set; }
    public int BillingStatusId { get; set; }
    public Nullable<System.Guid> ProjectId { get; set; }
    public Nullable<bool> Specialized { get; set; }
    public Nullable<int> TurnaroundId { get; set; }
    public Nullable<int> FromLanguage { get; set; }
    public Nullable<int> ToLanguage { get; set; }
    public Nullable<System.Guid> ParentFileId { get; set; }
    public virtual ICollection<FileService> FileServices { get; set; }
    public virtual ICollection<FileAudioVariable> FileAudioVariables { get; set; }
    public virtual ServiceTurnaround ServiceTurnaround { get; set; }
    public virtual Project Project { get; set; }
    public virtual ICollection<FileLanguage> FileLanguages { get; set; }
    public virtual Language Language { get; set; }
    public virtual Language Language1 { get; set; }
}