I have a WCF service and I'm sharing types with a client in a shared assembly.
If the client create a derived class will it be possible to pass back the derived type to the service so that I can read the added properties through reflection ?
I tried but having issues with KnownTypes since the service don't know how to deserialize the derived type.
[Serializable]
public abstract class Car : ICar
{........
//on the client :
[Serializable]
public class MyCar : Car
{......
when passing myCar to Service I get the exception complaining about knownType but I cant add this on the server since I wont know what the client will be sending through and I want to handle extra properties through reflection.
Possible to register client types as knowntypes at runtime ?
Is this maybe the solution ?
http://blogs.msdn.com/b/sowmy/archive/2006/03/26/561188.aspx
This is not possible. Both service and client has to know what types will be sent in messages. If you want to use known type you have to define that relation to parent type on the service.
Why do you need to know added properties on the server?
I think there is a way.
I vaguely remember that when I studied WCF, I met ExtensionData which should be a mechanism to get everything that does not match the serialization of the class. for example, if you enable ExtensionData and you are in this situation
//Server
public class GenericRQ
{
public string GenericProperty {get;set;}
}
public Service GenericService
{
Public void GenericMethod(GenericRQ RQ)
{
}
}
// client
Public class MoreSpecificRQ : GenericRQ
{
public string SpecificProperty {get;set;}
}
At
Public void GenericMethod(GenericRQ RQ)
{
// the serializer adds automatically in RQ.ExtensionData everything that has come and that does not match the class GenericRQ.
}
On how to enable ExtensionData you to easily search on the web
Related
I have:
[DataContract]
public class A
{
[DataMember]
public int X { get; set; }
}
[DataContract]
[KnownType(typeof(Derived<A>))]
public class Base {}
[DataContract]
public class Derived<T>: Base {
[DataMember]
public T Data {get; set; }
}
Service method returns IEnumerable of Base class containing object of Derived class.
Auto-generated WCF client retrieves data and correctly detects type and creates instances of the Derived class, but Derived.Data.X is not mapped, i.e. has 0. The soap message received is correct.
Any ideas why the generic property of the derived class is not correctly mapped from the soap message in the client?
I strongly recommend you to avoid generics in service contracts. SOA world is not friendly with generic type in the service contract. Please look problems reported by others:
Error when updating service reference.The URI prefix is not recognized
WCF. Service generic methods
WCF generic property is not mapped in derived class
http://social.msdn.microsoft.com/Forums/vstudio/en-US/2a9a2fc6-9e01-4112-8948-4192c516c6e7/how-to-use-generics-in-wcf-service
I have a class Car
public class Car
{
private Member _owner;
public string OwnerName
{
get { return _owner.Name; }
}
public Car(Member owner)
{
_owner = owner;
}
}
I'm using it both at Silverlight application and wcf service
So, at application I call WCF service to give me instance of car class, but when I get it at application, I see that _owner is empy.
I know that it is empty because of private, but how can I deal with it?
I'm using this class in my app as model (MVVM) if it could helps :/
For a start none of your properties are marked as DataMembers. The class isn't marked as a DataContract. If this is getting returned from a WCF service I would expect to see:
[Serializable]
[DataContract]
public class Car
{
private Member _owner;
[DataMember]
public string OwnerName
{
//getter
//setter
}
etc..
}
Does Member have to be private? Could it be converted into a property?
Keep in mind that a [DataMember] property needs both a set and a get (so that WCF can read into and from the object).
http://msdn.microsoft.com/en-us/library/ms733127.aspx
From a WCF serialization point of view, your Car class actually looks something like this to the WCF service:
public class Car
{
public string OwnerName { get; set; }
//other public properties here....
}
The WCF serializer uses the .NET class definition as a template for serializing its contents as a simple data transfer object. When the WCF service sends back a Car instance, only the public properties will contain values. The serializer ignores all methods in the class. Also, later versions of WCF don't require the DataContract/DataMember attribute markup.
The _owner variable is never initialized because it is not part of the public properties of the Car class. You'll need to modify the structure of the Car class (maybe add a public Owner property of type Member) to get all the data sent from the WCF service to your client.
When you are using the default Data Contract Serializer with WCF services it serializes and deserializes only the public properties of the class. Also another thing to note is that while deserializing the object graph the constructor is not called. You can have a public property with getter and setter.
Here is a very nice article by Jeremy Likeness explaining the problem similar to yours. From Architecture as well as best practices point of view you can use a POCO class generally called as DTO (Data Transfer Object) when transferring objects between the service layer and the clients.
I am having problems creating WCF client proxy for service code like in this example:
// data classes
[KnownType(typeof(ClassA))]
[KnownType(typeof(ClassB))]
public abstract class BaseClass : Dictionary<string, ITest>
{
}
public class ClassA : BaseClass
{
}
public class ClassB : BaseClass
{
}
public interface ITest
{
}
// service
[ServiceContract]
public interface IService1
{
[OperationContract]
BaseClass Method();
}
public class Service1 : IService1
{
public BaseClass Method()
{
...
}
}
Whenever I try to create a WCF proxy using "Add Service Reference" in VS it fails and trace log says
Type 'WcfProxyTest.ClassA' cannot be added to list of known types since another type 'WcfProxyTest.ClassB' with the same data contract name 'http://schemas.microsoft.com/2003/10/Serialization/Arrays:ArrayOfKeyValueOfstringanyType' is already present. If there are different collections of a particular type - for example, List<Test> and Test[], they cannot both be added as known types. Consider specifying only one of these types for addition to the known types list.
I can see what the error message is saying, but is there any other way around this (other than refactoring the classes). I am dealing with a legacy system which has classes written in the same manner as in my example and rewriting them is not an option as this stuff sits in the very core of the system :S
Any ideas? Thanks!
I decided to refactor the code in such a way that I don't have to provide two KnownTypes which gets me around the problem. About 300 syntax errors later that worked. I would be interested in any other ways of doing it though...
Try adding:
[KnownType(typeof(Dictionary<string, ITest>))]
I'm trying to take a datacontract object that I received on the server, do some manipulation on it and then return an upcasted version of it however it doesn't seem to be working. I can get it to work by using the KnownType or ServiceKnownType attributes, but I don't want to roundtrip all of the data. Below is an example:
[DataContract]
public class MyBaseObject
{
[DataMember]
public int Id { get; set; }
}
[DataContract]
public class MyDerivedObject : MyBaseObject
{
[DataMember]
public string Name { get; set; }
}
[ServiceContract(Namespace = "http://My.Web.Service")]
public interface IServiceProvider
{
[OperationContract]
List<MyBaseObject> SaveMyObjects(List<MyDerivedObject> myDerivedObjects);
}
public class ServiceProvider : IServiceProvider
{
public List<MyBaseObject> SaveMyObjects(List<MyDerivedObject> myDerivedObjects)
{
... do some work ...
myDerivedObjects[0].Id = 123;
myDerivedObjects[1].Id = 456;
myDerivedObjects[2].Id = 789;
... do some work ...
return myDerivedObjects.Cast<MyBaseObject>().ToList();
}
}
Anybody have any ideas how to get this to work without having to recreate new objects or using the KnownType attributes?
I think that your problem is that you are trying to send over a generic list.
It will work if you encapsulate the list in an object. That is create an object with a single public property which is the generic list.
You also need to make sure that all classes that are not used directly in the contract are marked as serializable.
If you want to return the derived objects then there will always be a round trip because the client and the service are separate. In order for the client to update its own list of MyBaseObjects it has to deserialize the list of MyDerivedObjects that came from the server.
The use of KnownType and/or ServiceKnownType is needed because this leads to the addition of that type information into WSDL, which is in turn used by the client to deserialize the messages to the correct type.
For starters, a useful tool for testing the scenario you've described: http://www.wcfstorm.com
You might try creating a DataContractSurrogate (IDataContractSurrogate) and returning your base type for the call to GetDataContractType. I'm not really sure that's how it was intended to be used so you still may be better of with "the extra work", but maybe I don't understand the scope of that extra work.
One of the problems with WCF (and .net remoting) is that it they tries to make “message passing” look like method calls.
This fall down when you try to use too many “oop” type designs.
The fact that the messages are
represented by .net classes, does not
make all of their behaviour like .net
class.
See this, and this, for more on the problem of Leaking Abstraction.
So you need to start thinking about message passing not object when designing your WCF interfaces, or you will hit lots of problems like this.
I know that a private parameterless constructor works but what about an object with no parameterless constructors?
I would like to expose types from a third party library so I have no control over the type definitions.
If there is a way what is the easiest? E.g. I don't what to have to create a sub type.
Edit:
What I'm looking for is something like the level of customization shown here: http://msdn.microsoft.com/en-us/magazine/cc163902.aspx
although I don't want to have to resort to streams to serialize/deserialize.
You can't really make arbitrary types serializable; in some cases (XmlSerializer, for example) the runtime exposes options to spoof the attributes. But DataContractSerializer doesn't allow this. Feasible options:
hide the classes behind your own types that are serializable (lots of work)
provide binary formatter surrogates (yeuch)
write your own serialization core (a lot of work to get right)
Essentially, if something isn't designed for serialization, very little of the framework will let you serialize it.
I just ran a little test, using a WCF Service that returns an basic object that does not have a default constructor.
//[DataContract]
//[Serializable]
public class MyObject
{
public MyObject(string _name)
{
Name = _name;
}
//[DataMember]
public string Name { get; set; }
//[DataMember]
public string Address { get; set; }
}
Here is what the service looks like:
public class MyService : IMyService
{
#region IMyService Members
public MyObject GetByName(string _name)
{
return new MyObject(_name) { Address = "Test Address" };
}
#endregion
}
This actually works, as long as MyObject is either a [DataContract] or [Serializable]. Interestingly, it doesn't seem to need the default constructor on the client side. There is a related post here:
How does WCF deserialization instantiate objects without calling a constructor?
I am not a WCF expert but it is unlikely that they support serialization on a constructor with arbitrary types. Namely because what would they pass in for values? You could pass null for reference types and empty values for structs. But what good would a type be that could be constructed with completely empty data?
I think you are stuck with 1 of 2 options
Sub class the type in question and pass appropriate default values to the non-parameterless constructor
Create a type that exists soley for serialization. Once completed it can create an instance of the original type that you are interested in. It is a bridge of sorts.
Personally I would go for #2. Make the class a data only structure and optimize it for serialization and factory purposes.