WCF - Questions - 1

1. What are the contracts WCF provides?
• ServiceContract
• OperationContract
• DataContract
• MessageContract
• FaultContract 
2. How the contracts are implemented?
• All the above contracts are implemented using Attributes
3. What are the Message Exchange Patterns in WCF
• Request-Response
• Oneway
• Duplex
4. What is the different between Request-Response and Oneway Message exchange?
• OneWay - fire and forget. Message is sent and no reply is received
• HTTP status code: 202 - Accepted, protocol level ACKnowledgement, which indicates that the request has reached the service. That's it. No information after that.
• Request-Response - Message is sent and reply is received
• HTTP status code: 200 - OK
5. What is Duplex Message Exchange Pattern? When do you really use it? any real time example?
• Client sends arbitrary number of messages and it is received in any order at server.
6. What is the first step in writing a service?
• Define the Contract
7. Can a method which is exposed via [OperationContract(IsOneWay=true)], return values?
• No. While hosting the service exception will be thrown, at runtime.
• Unhandled Exception: System.InvalidOperationException: Operations marked with IsOneWay=true must not declare output parameters, by-reference parameters or return values.
8. What Serialization engine WCF uses?
• DataContractSerializer - to serialize and de-serialize data.
9.