I've pasted a blogpost I made about this below (link to blog) (Please check out the example project that demonstrates the issue)

Can anyone explain why creating a default constructor (defined in a partial class) of an auto-generated Service References class for an object. Does not get executed when the object is created by a WCF service call?

I'll go through some of the basic steps I did to reproduce this, and I'll attach the project I created to do so. I would love if anyone had some insight into this... SilverlightWcfConstructorTest.zip

1. Create a web service that returns some complex type. (Class1)

2. Create a Silverlight app that can consume the service above. (Use the Add Service Reference so it will auto-generate a service reference file).

3. (in Silverlight) Create a partial class to extend the Class1 created by the service reference

4. Add a default constructor to this partial class.

5. Do something in this constructor to hint that it is called.

6. Run it and see that the default constructor is never called when making a WCF Silverlight service call.

 trace the code in the reference file back to where Class1 is created...

 In EndDoWork:

SilverlightWcfConstructorTest.ServiceReference1.Class1 _result = ((SilverlightWcfConstructorTest.ServiceReference1.Class1)(base.EndInvoke("DoWork", _args, result)));

The silverlight client-side doesn't use the implicit default constructor in the autogenerated class to create it, and thus your overwrite in the partial class will never get called either.

 i'm not sure why you think the way this works is incorrect.  this is how ws and wcf work; there's no security issue involved.  you do realize that if you had an explicit constructor on the server that it would get called, right?

what are you trying to accomplish?

Yes in WCF you can use [OnDeserialized] attribute

But it haven't been included in SL2 runtime ;(((

Shame!

 Oops....I got the same problem, too.....any suggestion to hook up the propertychanged event

 How the client-side object to be created? why the default constructor doesn't be called? 

Dear Sergey,

Thank you for your reply.

==>which creates instance WITHOUT calling any constructors... so forget all "constructors fire first" rules ;)
OK...I will keep it in mind.


==>use DataMember's Order parameter ;)
would you mind I am asking for more detail, please?
thank you

How does WCF deserialization instantiate objects without calling a constructor?

reference:http://stackoverflow.com/questions/178645/how-does-wcf-deserialization-instantiate-objects-without-calling-a-constructor

The solution I have settled on is to implement the MVVM pattern.  The ViewModel is now a completely seperate class that is fully under my control and I can extend it any way I see fit.  The drawback of couse is that the proxy class that is created with the Web Service reference now has to be synchronized with my ViewModel when the web service call completes.

 Not ideal, but it works.