c# - 如何编写数据传输对象？

Question

在我的 N 层架构中，我有 DTO (AddressResponseDTO)，其中有大约 20 个属性。当表示层向我的业务层请求（AddressRequestContext）特定搜索操作的响应时，我会将此 DTO（AddressResponseDTO）发送给 PL。

但情况并非总是如此。地址搜索请求将被更改有时我只需要发送它的 3 个属性（比如说城市、邮编和地址计数），有时它可能是 5 个。所以我仍然可以拥有具有 20 个属性的相同 DTO 来重用所有类型的搜索要求。

Answer 1

As the OP states that sometimes only 3 of the properties are used, there can be several solutions:

• Create a DTO with all the properties, and specifiy special values to show which properties aren't specificed (i.e. use nullables, or special values). This requires lots of checkings in the code.

• Create a DTO with the 3 properties. Inherit a second DTO from this and add all the remaining properties. Your methods can receive the base class as parameter and check if a base or derived class is received. A simple check like if (myDto is DtoBase) ... will quickly show which properties have been sent with the DTO. (This will work only for increasing number of properties, in a hierarchy of inherited DTOs)

• If there are more than one possible grouping of properties of interest, you can use a DTO class for each group and:

  • create a class which has this DTO as members. If you don't need them, leave them null. This way you can check each group with a simple if (containerDto.Dto1 != null)
  • define as many DTO parameters as you need for each case.

I don't like the "special value" way, because it requires more code and it's more error prone. Besides, it makes you (de)serialize more info than neccessary on many occasions.

Answer 2

编写具有 20 个属性的 DTO 并没有什么坏处。

但是，如果属性可以组合在一起，最好将相关属性组合成一个实体，就像您可以将 City、Zip 组合成一个地址一样。

Answer 3

是的，如果在这些情况下空属性或默认属性不会打扰您，您可以。从理论上讲，没有什么可以阻止您在所有情况下都使用一个类。

或者，您可以针对不同的用例创建多个 DTO 类定义。在这种情况下，我建议在这些类之间使用一些类层次结构。

我认为这取决于您以及您喜欢使用哪种方式的用例的复杂性。