我可以射出我的查询由EF生成的模型的结果？ [英] Can I project the result of my query to the model generated by EF?
问题描述
我有一个方法类似如下：
I have a method something like below :
public IEnumerable<CountryEF> GetAllCountry( )
{
using (Context context = new Context() )
{
List<CountryEF> countries = context.COUNTRY.Select(c =>
new CountryEF()
{
ID = c.ID,
Description = c.DESCRIPTION,
CURRENCYEF = c.CURRENCYEF
}
).ToList<CountryEF>();
return countries;
}
}
在哪里COUNTRYEF是一个模型类由实体框架生成看起来像这样：
Where COUNTRYEF is a Model Class Generated by Entity Framework which looks like this :
public partial class COUNTRYEF
{
public COUNTRYEF()
{
}
public string ID { get; set; }
public string DESCRIPTION { get; set; }
public virtual CURRENCY CURRENCYEF { get; set; }
}
当过我这样做，我得到异常。所以，作为一名后备我要创建另一个类，这是就像下面这样上面的类的复制粘贴：
When ever I do this I get Exception. So as a fallback I have to create another class which is just a copy-paste of above class like this below :
public class COUNTRYVM //view model class
{
public COUNTRYVM()
{
}
public string ID { get; set; }
public string DESCRIPTION { get; set; }
public virtual CURRENCY CURRENCYEF { get; set; }
}
然后我的查询变得像这样的：
And then my query becomes like this :
public IEnumerable<CountryVM> GetAllCountry( )
{
using (Context context = new Context() )
{
List<CountryVM> countries = context.COUNTRY.Select(c =>
new CountryVM()
{
ID = c.ID,
Description = c.DESCRIPTION,
CURRENCYEF = c.CURRENCYEF
}
).ToList<CountryVM>();
return countries;
}
}
和上述溶液工作正常和良好的。但我真的想复制由实体框架生成的模型类，如公共部分类COUNTRYEF 来像公共类COUNTRYVM 。我真的不想做code重复。
And the above solution works fine and good. But Do I really want to replicate the Model classes generated by Entity Framework like public partial class COUNTRYEF to something like public class COUNTRYVM. I really don't want to do code duplication.
什么是这种情况的可能的解决方案？
匿名特性也不要。我曾尝试以下解决方案：
What are the possible solutions for this ? Anonymous properties also dont. I had tried the below solution :
public IEnumerable GetAllCountry( )
{
using (Context context = new Context() )
{
var countries = context.COUNTRY.Select(c =>
new //Anonymous Projection
{
ID = c.ID,
Description = c.DESCRIPTION,
CURRENCYEF = c.CURRENCYEF
}
).ToList();
return countries;
}
}
但我不能访问ID，说明和CurrencyEF在我的视图和控制器！
But then I cannot access the ID , Description and CurrencyEF in my Views and Controllers!!
推荐答案
实体框架不允许创建实体类里面的投影。东西硬做它来跟踪它应该被跟踪的实体。周围的工作我用。而不是拷贝和粘贴类只是继承它。
Entity Framework doesn't allow creating classes of the Entity inside it's projection. Something to do with hard for it to track which entities it should be tracking. The work around I use. Instead of copy and pasting the class just subclass it.
public partial class CountryEFSub : CountryEF
{
}
public IEnumerable<CountryEF> GetAllCountry( )
{
using (Context context = new Context() )
{
return context.COUNTRY.AsNoTracking().Select(c =>
new CountryEFSub()
{
ID = c.ID,
Description = c.DESCRIPTION,
CURRENCYEF = c.CURRENCYEF
}
).AsEnumerable();
}
}
这在我还没有与其他任何版本中使用它EF 5.欺骗工作。也注意到你仍然可以保留方法类型CountryEF。
This tricked worked in EF 5. I haven't used it with any version else. Also noticed you can leave the method type still as CountryEF.
您可以创建一个T4为你创造的所有子类。此外，如果你需要用投影帮助，我相信AutoMapper现在支持IQueryable的。否则，你可以手工编写或与前presison树木的预测。
You could create a T4 to create all the subclasses for you. Also if you need help with the projections I believe AutoMapper now supports IQueryable. Otherwise you can write the projections by hand or with expresison trees.
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