CODEWITHSUNDEEP
c#wcf
Technica
Technica

Reputation: 37

SessionMode and InstanceContextMode difference in WCF

I am currently studying WCF sessions and after reading few articles on MSDN... one thing that I feel confusing is about Clear Difference between SessionMode and InstanceContextMode that we can use in WCF.

I know the different values that we can use for both these attributes but what exactly is the difference between these two methods?

Why there are these two methods in WCF?

Upvotes: 1

Views: 811

Answers (2)

S. Doe
S. Doe

Reputation: 23

Actually there is a difference between these two methods. The SessionMode is a property of the ServiceContract attribute. The ServiceContract attribute should be applied to interfaces. Whereas the InstanceContextMode property is a member of the ServiceBehaviour attribute, which is applied on the actual implementation of a service (class).

So with the SessionMode property you define wich type of SessionModes are allowed to be implemented on the actual service. And with the InstanceContextMode property you define the actual implemented behaviour of a service.

If the interface is marked with SessionMode.NotAllowed

[ServiceContract(SessionMode = SessionMode.NotAllowed)]
public interface IHelloService
{
    [OperationContract]
    string SayHello();
}

And the class is marked with InstanceContextMode.PerSession

[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession)]
public class HelloService : IHelloService
{
    private int _requestCount;
    public string SayHello()
    {
        _requestCount++;

        return $"Hello this is your {_requestCount} request";
    }
}

A System.InvalidOperationException will be thrown at runtime once you try to host the Service.

Remark: A weird thing I experienced. When you mark the interface with SessionMode.Required and mark the class with InstanceContextMode.PerCall, no exception is thrown and everythink works fine. Can anyone explain me why?

Upvotes: 1

Seymour
Seymour

Reputation: 7067

While the two values seem similar and in some ways interact, the settings actually control different aspects of the WCF service. The InstanceContextMode property is used to control when new service objects are created by the application. The SessionMode, on the other hand, indicates whether sessions are allowed, not allowed, or required.

Some additional links to review:
https://msdn.microsoft.com/en-us/library/system.servicemodel.servicecontractattribute.sessionmode(v=vs.110).aspx
https://msdn.microsoft.com/en-us/library/system.servicemodel.servicebehaviorattribute.instancecontextmode(v=vs.110).aspx

Upvotes: 0

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