WCF and ServiceKnownType with many assemblies - wcf

Question

WCF Question. I'm having trouble with multiple assemblies and inheritances and data contracts.
Senario: data contracts binaries are shared
Common.dll
[DataContract]
public abstract class Command
{
[DataMember]
public Guid Id { get; set; }
public Command(Guid id)
{
Id = id;
}
}
assembly1.dll
[DataContract]
public class DeleteStuff : Command
{
public DeleteStuff(Guid id)
: base(id) { }
[DataMember]
public int StuffToDeleteID { get; set; }
}
assembly2.dll
[DataContract]
public class DeleteSomeOtherStuff : Command
{
public DeleteSomeOtherStuff(Guid id)
: base(id) { }
[DataMember]
public int SomeOtherID { get; set; }
}
Service Contract
[ServiceContract]
[ServiceKnownType("GetKnownTypes", typeof(DerivedType))]
public partial interface ICommandsServiceContract
{
[OperationContract]
void Execute(IEnumerable<Command> command);
}
DerivedType class, method GetKnownTypes
public static IEnumerable<Type> GetKnownTypes(ICustomAttributeProvider provider)
{
//Works!*!*! but hard-coded, wont work in big picture since i dont know all the classes
//return new List<Type> { typeof(DeleteSomeOtherStuff), typeof(DeleteStuff) };
//DOESNT WORK!!
Type type = typeof(Command);
IEnumerable<Type> types = AppDomain.CurrentDomain.GetAssemblies().ToList()
.SelectMany(a => a.GetTypes()
.Where(t => type.IsAssignableFrom(t)));
IEnumerable<Type> j = types.ToArray();
return j;
}
If I put a break point on return j; above, when the service first runs it has the correct assembly types that inherit from Command. Then the client spins up and as soon as I send a DeleteSomeOtherStuff to the service it explodes with an error on the SelectMany clause.
Server Error in '/' Application.
Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.Reflection.ReflectionTypeLoadException: Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.
Source Error:
Line 25: var type = typeof(Command);
Line 26: var types = AppDomain.CurrentDomain.GetAssemblies().ToList()
Line 27: .SelectMany(a => a.GetTypes())
Line 28: .Where(t => type.IsAssignableFrom(t));
Line 29:
Line 27 is marked as the error.
I tried throwing the array list in a static variable to cache it when the service first runs and then it would be available when its called by a consumer but that had the same error.
I'm using a basic channel factory from the client.
Ideas?? I can't limit to a single assembly.
Thanks!!

Answer 1

In your classes that inherit from Command, add the [KnownType] attribute. For example,
[DataContract]
[KnownType(typeof(Command))]
public class DeleteStuff
{
}