如何将实体的一部分公开为DataContract? [英] How to expose part of Entity as DataContract?

问题描述

到目前为止，在使用WCF时，我一直将整个EF生成的实体或POCO(通过修改T4模板以将POCO和属性上的DataContract和DataMember包括在内)公开为DataContract.

Up to now, when working with WCF, I have always been exposing the whole either EF generated entities, or POCOs(by modifying the T4 template to include DataContract and DataMember on POCOs and properties) as DataContract.

现在，我遇到了一种情况，我无法公开全部内容，需要显式指定我的DataContract作为实体的子集.

Now, I have come across a situation that I cannot expose the whole thing, and need to explicitly specify my DataContract to be a subset of the entities.

值得一提的是，我的一个实体如下所示:

It worth saying that one of my entities is something like below:

我只想公开ID，名称，CategoryId，价格.

And I want to just expose Id, Name, CategoryId, Price.

插入/更新其余字段(ActiveFrom，InactiveDate，Supported)是根据BR确定的，并且客户端不知道，也不应该确实知道关于以下内容的任何信息他们.

Insert/Update of rest of the fields (ActiveFrom, InactiveDate, Supported) is something that will be decided based on the BR, and client doesn’t know , and should not know indeed, anything about them.

我尝试了以下方法，但是每种方法似乎都存在问题/不起作用:

I have tried following approaches, but each of them seems to have problem/not working:

1. 使用 AutoMapper :我需要将源对象映射到 目标对象，这是一个单向映射，因此对于 演示目的我可以将Product映射到ProductContract.但是对于添加/更新产品，它确实 无法工作，因为它无法进行双向映射.

1. Using AutoMapper : I need to map a source object to a destination object, and this is a one way mapping, so for presentation purposes I can map Product to ProductContract. But for adding/updating the product, it does not work as it cannot do a two way mapping.

使用反射并为实体和 将[DataMember]属性添加到Metadata类的属性，如下所示 (请注意，我还没有包含不需要的字段):

Use the reflection and create a metadata class for the entities and add the [DataMember] attribute to the properties of the Metadata class as below (please note that I haven’t included the unwanted fields):

public class ProductMD : AssociatedMetadataTypeTypeDescriptionProvider
    {
        public ProductMD() :
            base(typeof(Product))
        {
        }
        [DataMember]
        public int Id{ get; set; }

        [DataMember]
        public string Name { get; set; }

        [DataMember]
        public int? CategoryID { get; set; }

        [DataMember]
        public decimal? Price { get; set; }
    }

，然后将ProductMD用作Product的属性 不接触自动生成的实体的局部类(仅供参考:我有 更改了POCO T4模板生成器以包括 每个实体上的[DataContract]):

And then use the ProductMD as an attribute for the Product partial class without touching the auto-generated entity (FYI: I have changed the POCO T4 template generator to include the [DataContract] on each entity):

[MetadataType(typeof(ProductMD))]
public partial class Product
{  
}

但是在客户端，我没有 访问产品的任何DataMembers.

But on the client side, I do not have access to any of the DataMembers of the Product.

现在我的问题是，获得我想要做的最好的方法是什么(将实体的子集显示为DataContract)?

Now my question is that, what is the best approach to gain what I want to do (exposing a subset of the entities as DataContract)?

推荐答案

我会选择选项1-> AutoMapper.

I would go with option 1 -> AutoMapper.

它无法工作，因为它无法进行双向映射.

it does not work as it cannot do a two way mapping.

您可以定义两种方式的映射:

You could define two way mapping:

Mapper.CreateMap<Product, ProductContract>();
Mapper.CreateMap<ProductContract, Product>();

很明显，如果在进行映射时ProductContract中的属性少于域模型中的属性，则只会填充相应的属性.

obviously if in your ProductContract you have less properties than in your domain model when doing the mapping, only the corresponding properties will be populated.

在进行逆映射更新时，您可以执行以下操作:

When doing the inverse map for updating you could do the following:

ProductContract pc = ...
Product productToUpdate = GetProduct(pc.Id);
Mapper.Map<ProductContract, Product>(pc, product);
// at this stage the product model will have the properties that
// were present in the ProductContract being mapped from them and
// the rest of the properties will stay unmodified, i.e. they will
// have their initial values that were retrieved from the database.
// Now we can update the product:
UpdateProduct(product);

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