Serializing types that return interfaces instead of instances in WCF 3.5 SP1
I came across interesting problems with WCF serialization specifically the DataContractSerializer and limitations of the runtime.
Say you have a class like so
[Serializable]
public class Service
{
public IList<Person> People
{
get; set;
}
}
[Serializable]
public class Person
{
public string Name
{ get; set; }
public string Address
{ get; set; }
}
If you try to get this working in a WCF service it won’t work, basically the problem is that you are returning an interface, not a concrete type, and the serializer doesn’t know how to deal with it. To allow this to work you basically have to implement a data contract for the types invovled, then it seems to understand, and also adding a KnownType attribute helps it to serializer things without getting generic random errors on the service.
[ServiceContract]
[KnownType(typeof(Person))]
public class Service
{
[DataMember]
public IList<Person> People
{
get; set;
}
}
[DataContract]
public class Person
{
[DataMember]
public string Name
{ get; set; }
[DataMember]
public string Address
{ get; set; }
}
Another common issue is that best practices say your shouldn’t have setters on a collection, but let users add to it or remove, from the collection itself. the WCF serializer requires read/write access to the collection for its duty, so a way around it is to do this
[ServiceContract]
[KnownType(typeof(Person))]
public class Service
{
[DataMember(Name = "People")]
private List<Person> people = new List<Person>();
public IList<Person> People
{
get
{
return people;
}
}
}
[DataContract]
public class Person
{
[DataMember]
public string Name
{ get; set; }
[DataMember]
public string Address
{ get; set; }
}
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