Error in getting a custom object inherited from a base class using web method ASP.NET

Hi

I have created a base class A and a class B is a derived class inherited from class A. Both classes are marked as Serialized. When I try to return an object of type B through a web method i am getting following error:

System.Web.Services.Protocols.SoapException: System.Web.Services.Protocols.SoapException: Server was unable to process request. ---> System.InvalidOperationException: There was an error generating the XML document. ---> System.InvalidOperationException: The type CSI.API.RPartyMembershipInfo was not expected. Use the XmlInclude or SoapInclude attribute to specify types that are not known statically.

Any help would be appreciated.

From stackoverflow

• You will need to post your code before we can provide some help.

  I did a quick search for the final line of the error message in Google and got these 2 pages which might be of help.

  http://www.theserverside.net/discussions/thread.tss?thread_id=37823

  http://social.msdn.microsoft.com/Forums/en-US/asmxandxml/thread/aa18e76b-0efc-4c5c-be28-5fb578cf47f2/

  Sunny : The second link should help, it has all the information needed.