on wcf type is not expected even though its on ServiceKnownType(typeof(...))

i am using third party classes in my service, so i cant edit them.

third party

[Serializable]  
Class B : E  

[Serialazable]  
Class E : A  

service

[ServiceKnownType(typeof(B))]  
[ServiceKnownType(typeof(E))]  
fun(A pic)  

client

for some reason :

prox开发者_JS百科y.fun(object)  

throw an exception that B is unexpected and add it to the datacontractSerializer KnownTypes

what reason can it be ?.

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Are you applying the ServiceKnownType attribute on the service contract or the service implementation? The ServiceKnownType attribute is meant to be to be used on your contract interface.

http://msdn.microsoft.com/en-us/library/system.servicemodel.serviceknowntypeattribute.aspx