should I ever put a major version number into a C#/Java namespace?
- by Andrew Patterson
I am designing a set of 'service' layer objects (data objects and
interface definitions) for a WCF web service (that will be consumed
by third party clients i.e. not in-house, so outside my direct control).
I know that I am
not going to get the interface definition exactly right - and am
wanting to prepare for the time when I know that I will have to
introduce a breaking set of new data objects. However, the reality
of the world I am in is that I will also need to run my first version
simultaneously for quite a while.
The first version of my service will have URL of
http://host/app/v1service.svc
and when the times comes by new version will live at
http://host/app/v2service.svc
However, when it comes to the data objects and interfaces, I
am toying with putting the 'major' version of the interface number
into the actual namespace of the classes.
namespace Company.Product.V1
{
[DataContract(Namespace = "company-product-v1")]
public class Widget
{
[DataMember]
string widgetName;
}
public interface IFunction
{
Widget GetWidgetData(int code);
}
}
When the time comes for a fundamental change to the service, I will introduce
some classes like
namespace Company.Product.V2
{
[DataContract(Namespace = "company-product-v2")]
public class Widget
{
[DataMember]
int widgetCode;
[DataMember]
int widgetExpiry;
}
public interface IFunction
{
Widget GetWidgetData(int code);
}
}
The advantages as I see it are that I will be able to have a single
set of code serving both interface versions, sharing functionality
where possible. This is because I
will be able to reference both interface versions as a distinct
set of C# objects. Similarly, clients may use both interface
versions simultaneously, perhaps using V1.Widget in some legacy
code whilst new bits move on to V2.Widget.
Can anyone tell why this is a stupid idea? I have a nagging feeling
that this is a bit smelly..
notes:
I am obviously not proposing every single new version of the service
would be in a new namespace. Presumably I will do as many
non-breaking interface changes as possible, but I know that I
will hit a point where all the data modelling will probably need a
significant rewrite.
I understand assembly versioning etc but I think this question is
tangential to that type of versioning. But I could be wrong.
