C# 4 and .NET 4

service implementation ❘ 1295
serViCebehaVior ProPerTy
ConcurrencyMode
UseSynchronizationContext
IncludeExceptionDetailInFaults
MaxItemsInObjectGraph
ValidateMustUnderstand
desCriPTion
Because stateful objects can be used by multiple clients (or
multiple threads of a single client), you must pay attention to
concurrency issues with such object types. If the property
ConcurrencyMode is set to Multiple, multiple threads can
access the object, and you must deal with synchronization. If
you set the option to Single, only one thread accesses the
object at a time. Here, you don’t have to do synchronization;
however, scalability problems can occur with a higher number of
clients. The value Reentrant means that only a thread coming
back from a callout might access the object. For stateless
objects, this setting has no meaning, because new objects are
instantiated with every method call and thus no state is shared.
With Windows Forms and WPF, members of controls can be
invoked only from the creator thread. If the service is hosted
in a Windows application, and the service methods invoke
control members, set the UseSynchronizationContext
to true. This way, the service runs in a thread defined by the
SynchronizationContext.
With .NET, errors show up as exceptions. SOAP defines
that a SOAP fault is returned to the client in case the server
has a problem. For security reasons, it’s not a good idea to
return details of server-side exceptions to the client. Thus, by
default, exceptions are converted to unknown faults. To return
specific faults, throw an exception of type FaultException.
For debugging purposes, it can be helpful to return the real
exception information. This is the case when changing the
setting of IncludeExceptionDetailIn Faults to true. Here
a FaultException is thrown where the original
exception contains the detail information.
With the property MaxItemsInObjectGraph, you can limit
the number of objects that are serialized. The default limitation
might be too low if you serialize a tree of objects.
The property ValidateMustUnderstand set to true means
that the SOAP headers must be understood (which is the
default).
To demonstrate a service behavior, the interface IStateService defines a service contract with two
operations to set and get state. With a stateful service contract, a session is needed. That’s why the
SessionMode property of the service contract is set to SessionMode.Required. The service contract
also defines methods to initiate and close the session by applying the IsInitiating and IsTerminating
properties to the operation contract:
[ServiceContract(SessionMode=SessionMode.Required)]
public interface IStateService
{
[OperationContract(IsInitiating=true)]
void Init(int i);
[OperationContract]
void SetState(int i);
[OperationContract]
int GetState();
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