WCF Message Contract real-world example - wcf

Question

I have searched multiple resources on the internet but all I have encountered is 'Hello World' and 'Calculator' like examples explaining Message Contract in WCF. I would like to know the practical usage of Message Contract in real-world enterprise applications and also when it should be preferred over Data Contract. Any help regarding this would be highly appreciated.

Answer 1

A real live scenario is for example, when a Java client has a WSDL file which doesn’t change (technical reason). So the Java client has a fixed WSDL file. Then the web service (.net) must have to provide this method with the exact name, namespace, action and message string.
Example Java client:
<operation name="remove">
<input wsam:Action="remove" message="tns:remove"/>
<output wsam:Action="removeResponse" message="tns:removeResponse"/>
</operation>
Default is in the web service automatic generated, something like this:
<wsdl:operation name="remove">
<wsdl:input message="tns:IService1_remove_InputMessage" wsaw:Action="http://tempuri.org/IService1/remove"/>
<wsdl:output message="tns:IService1_remove_OutputMessage" wsaw:Action="http://tempuri.org/IService1/removeResponse"
</wsdl:operation>
Then server and client get a mismatch error, because the client cannot find the method. To solve this problem you have to change the action, replyAction and message string. The first and second one you must change with:
<OperationContractAttribute(Action:="remove", name:="remove" ReplyAction:="removeResponse")> _
Function remove(key As string) As Boolean
new WSDL file(server):
<wsdl:operation name="remove">
<wsdl:input message="tns:IService1_remove_InputMessage" wsaw:Action="remove"/>
<wsdl:output message="tns:IService1_remove_OutputMessage" wsaw:Action="removeResponse"
</wsdl:operation>
Now you still get the same mismatch error, because the message string isn’t the same. To solve this you need Message Contract. This enable you to manipulate the WSDL file/SOAP Message.
For this the syntax of the method changes inside the IService class.
<OperationContractAttribute(Action:="remove", name:="remove" ReplyAction:="removeResponse")> _
Function remove(key As remove) As removeResponse
and the Message Contract definite the ‘type’:
<MessageContract()> _
Public Class removeResponse
Private return1 As Boolean()
<DataMember(Name:="return")> _
Public Property returnP() As Boolean ()
Get
Return Me.return1
End Get
Set(ByVal value As Boolean ())
Me.return1 = value
End Set
End Property
End Class
<MessageContract()> _
Public Class remove
Private key1 As String()
<DataMember(Name:="key")> _
Public Property keyP() As String ()
Get
Return Me.key1
End Get
Set(ByVal value As String ())
Me.key1 = value
End Set
End Property
End Class
Now the communication between client and server is ok.
WSDL(server):
<wsdl:operation name="remove">
<wsdl:input message="remove" wsaw:Action="remove"/>
<wsdl:output message="removeResponse" wsaw:Action="removeResponse"
</wsdl:operation>