text: Q:
  
  WCF service not generating classes for run time polymorphism
  
  I created my base class A with several inherited class A1, A2, A3 and so on.
  Now, using WCF service I am trying to return List which holds objects that can be of type A1, A2 or even A.
  Do WCF supports this? I am getting connection closed error continuously.
  eg.
  class A{
  //do something
  }
  
  class B:A{
  //do something
  }
  
  class C:A{
  //do something
  }
  
  WCF Service calling GetAll method which returns
  
  public List<A> GetAll()
  {
  var obj= new List<A>();
  obj.Add(new B());
  obj.Add(new C());
  return obj;
  }
  
  Now WCF service only have a knowledge about A but not B and C. How can I still return this object. As per oops this is valid but I don't know about service
  
  A:
  
  I was able to fix this by adding KnownType attribute to my class that is being exposed by service.
  http://msdn.microsoft.com/en-us/library/ms730167.aspx
  KnownType resolves serialization at runtime
  [KnownType(typeof(B))]
  [KnownType(typeof(C))]
  class A{
  //do something
  }
  
  class B:A{
  //do something
  }
  
  class C:A{
  //do something
  }
  
  