Does upgrading a WCF service from .NET 3.5 to 4.0 change the contract?

Question

If I upgrade a WCF Web Service from .NET 3.5 to 4.0, making no other changes, is there any risk of a change to the contract exposed to the outside world? ie. Will my consumers need to reconsume the WSDL?

If so, is there anything I can do to stop that happening?

EDIT: An example of the kind of thing I'm talking about.

We have been using something like this for a while http://www.codeproject.com/KB/aspnet/WSSecurityProvider.aspx

I may be reading this wrong but when I upgraded the server and reconsumed from the client, the Reference.cs changed so that

public MyNamespace.MembershipUser RemoteMembershipProvider_CreateUser(out System.Web.Security.MembershipCreateStatus status, string providerName, string applicationName, string username, string password, string email, string passwordQuestion, string passwordAnswer, bool isApproved, object providerUserKey) {
    return base.Channel.RemoteMembershipProvider_CreateUser(out status, providerName, applicationName, username, password, email, passwordQuestion, passwordAnswer, isApproved, providerUserKey);
}

changed to

public MyNamespace.MembershipUser RemoteMembershipProvider_CreateUser(out MyNamespace.MembershipCreateStatus status, string providerName, string applicationName, string username, string password, string email, string passwordQuestion, string passwordAnswer, bool isApproved, object providerUserKey) {
    return base.Channel.RemoteMembershipProvider_CreateUser(out status, providerName, applicationName, username, password, email, passwordQuestion, passwordAnswer, isApproved, providerUserKey);
}

Note the change in namespace for MembershipCreateStatus.

(and no, I don't really have a namespace called MyNamespace)

Am I wrong in thinking that if I hadn't reconsumed, it would have stopped working?

And if not, what is the specific thing that has change and how many other cases will it effect? Just framework enums? Or more than that?

Answer 1

No, there shouldn't be any issues - after all, all that travels between the client and the server is the serialized message.

The client really doesn't care what OS or .NET version the server is on - as long as the message can be understood and interpreted.

As long as you don't change anything, you should be just fine!