动态注释/属性值

Question

I run into a problem using data annotations in c#. I am using custom required and range attributes and I want to set an object as the error message.

[MyOwnRequired(ErrorCode=GlobalMessages.Message01]
public string Description { get; set; }

The problem is that I do have a class holding several objects (GlobalMessages.Message01, each containing a message and a code) in order to translate different error messages throughout the application.

As several articles states it is not possible to use a non constant expression as data annotations/attributes. I can not use enums to solve this problem since I need to extend the error messages in different projects which is not allowed with enums (inheritance). I also do not want to use the ErrorCode as a String since I want to see the message on each attribute (hover).

Does anyone have a good solution for this problem?

Answer 1

All true. You can not. Despite you wrote you can not use enums, this actually can serve a solution:

Pass enum parameter to your attribute and use this parameter in the attribute constructor's logic/algorithm to implement your extended logic.

Note: This is exactly opposite of some DPs so we safely can call it antipattern, but there is no other choice here.

If this is an important and verbose part of your project(s) then using an antipattern here could be a productivity killer. This case you can also use code generation to generate a partial part of your attribute, and generate the gigantic switch (and its logic) in the constructor automatically, based on some changes in the project. This eliminates most of the practical drawbacks of the antipattern. (well, it still remains ugly) Recommended tooling this case is T4 which has wide support.