c# - Context.Entry().GetDatabaseValues() 方法不会复制实体的子级

Question

我正在使用 Entity Framework 开发 WPF 项目。我使用 Context.Entry().GetDatabaseValues() 方法来获取正在更新的对象的原始对象值。 .GetDatabaseValues() 方法返回原始值，内部对象为空值

如下:

public partial class LabPayments 
{
   public partial class LabAccount
   {
    public long ID { get; set; }
    public Nullable<long> MaterialID { get; set; }
    public Nullable<long> LabID { get; set; }
    public Nullable<double> Quantity { get; set; }
    public Nullable<System.DateTime> MaterialDate { get; set; }
    public Nullable<long> LabMaterialPriceID { get; set; }
    public Nullable<decimal> Price { get; set; }

    public virtual Lab Lab { get; set; }
    public virtual LabMaterial LabMaterial { get; set; }
    public virtual LabMaterialPrice LabMaterialPrice { get; set; }
}

返回的虚拟对象值为空!!

Answer 1

来自 MSDN:

Queries the database for copies of the values of the tracked entity as they currently exist in the database.
^{_{https://msdn.microsoft.com/en-us/library/system.data.entity.infrastructure.dbentityentry.getdatabasevalues(v=vs.113).aspx}}

using (var context = new BloggingContext()) 
{ 
    var blog = context.Blogs.Find(1); 

    var clonedBlog = context.Entry(blog).GetDatabaseValues().ToObject(); 
}

Note that the object returned is not the entity and is not being tracked by the context. The returned object also does not have any relationships set to other objects.
^{_{https://msdn.microsoft.com/en-us/data/jj592677.aspx}}

---

GetDatabaseValues 仅获取跟踪实体的值，而不是任何导航属性或集合属性，它们只是关系/关联的表示。这些虚拟属性是对相关实体对象的引用，不会通过 GetDatabaseValues 返回。