VS.net creates a template when you create a WCF project.
It adds a class to the iService1.cs file:
// Use a data contract as illustrated in the sample below to
// add composite types to service operations.
[DataContract]
public class CompositeType
{
bool boolValue = true;
string stringValue = "Hello ";
[DataMember]
public bool BoolValue
{
get { return boolValue; }
set { boolValue = value; }
}
[DataMember]
public string StringValue
{
get { return stringValue; }
set { stringValue = value; }
}
}
Since a WCF service can return any user defined class, why use a DataContract and CompositeType class?
I can return something like:
[OperationContract]
MyUserCollection GetUsers();
What am I missing?
Best Answer
The DataContract is just a formal definition of a type that can be understood on both sides of the service boundary.
If you return, as in your example, a "MyUserCollection" object, the consumers of your service will need to reference the innards of your service/system, which is a violation of the SOA tenet of explicit boundaries. By using a DataContract, you are publishing the structure of your return types in a loosely-coupled way.