How to decide between Message Contract and Data Contract in WCF?

I am reading so many things to understand various things in WCF.

Very soon, actually, i want to move/convert existing WSE3 web services to WCF. In existing WSE web services, I have some (data) classes that model entities in our environment.

While transforming those classes, should I use Data Contract/Data Member attribute or the MessageContract attribute?

1. How to decide between Message Contract and Data Contract in WCF? 2. Does type of binding (like basicHttpBinding) has any role in this decision? 3. Does proxies created at client side (when we add web reference) change significantly depending on the Data or Message Contract?

(PS: I am trying to find a way so that existing WSE clients should be able to consume the WCF service without much alterations/modifications. Is it possible to use the current proxies generated from ASMX web services, to connect to the new WCF service just by setting URL of the proxy to WCF service?)

Solution

Here is a quick go at answering your questions:

1) Unless there is a specific reason like tweaking the structure of the soap XML, use DataContract instead of MessageContract.

2 & PS) Since you are currently using soap over HTTP, you'll most likely need the new services to be configured for basicHttpBinding. This will provide the interoperability that you need for the ASMX clients.

3) It shouldn't if the soap structure created by the WCF service matches your current soap.

I vaguely remember that WSE 3.0 supported some of the WS-* standards. If your current code depends on these then you may be able to also expose a wsHttpBinding for these operations but I don't think a default ASMX client works with a wsHttpBinding configured service.