I am looking at the new api that came out 2 weeks ago. It seems like
ReqDTO : IReturn<List<ResDTO>> { //... }
The "IReturn" bit seems to be optional? The DTOs in RazorRockstars demo project works without it.
This is a new addition in ServiceStack's New API which allows you to document the expected Response Type that the Request DTO will return, e.g. with
ReqDTO : IReturn<List<ResDTO>> { ... }
Which lets you call using any of the C# Service Clients with:
List<ResDTO> response = client.Get(new ReqDto());
If you didn't have the IReturn marker your client call would have to look like:
List<ResDTO> response = client.Get<List<ResDTO>>(new ReqDto());
Which is something the client/consumer of your service needs to know about. If you had the marker on the DTO the response type is already known.
The IReturn<> marker is also used to determine the Response DTO that's used in the HTTP Responses in ServiceStack's /metadata pages.
As far as I know, this is just a convenient way of defining your request/response DTOs. You're free to use it, or not.
In the case where you define your DTOs in a portable class library, you won't be able to use IReturn. Perhaps IReturn should be defined in a PCL in ServiceStack. Just a thought.
来源：https://stackoverflow.com/questions/12700702/servicestack-ireturn