Instance Context Mode in WCF

InstanceContextMode is used to control how service instances are allocated in response to client calls.

InstanceContextMode has following values:

•Single – One service instance is allocated for all client calls.

•PerCall – One service instance is allocated for each client call.

•PerSession – One service instance is allocated for each client session.

The default setting for InstanceContextMode is PerSession.

How to set InstanceContextMode  ?

Steps to set InstanceContextMode  in WCF :

1.Apply the ServiceBehaviorAttribute to the service class.

2.Set the InstanceContextMode property to one of the following values: PerCall, PerSession, or Single.

Per Session Service and Client

Per Session Service Code
[ServiceContract(Session = true)]
interface IMyContract
{
[OperationContract]
void MyMethod();
}

[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession)]
class MyService : IMyContract,IDisposable
{
int m_Counter = 0;

MyService()
{
Trace.WriteLine(“MyService.MyService()”);
}

public void MyMethod()
{
m_Counter++;
Trace.WriteLine(“Counter = ” + m_Counter);
}

public void Dispose()
{
Trace.WriteLine(“MyService.Dispose()”);
}
}

Client Code :
MyContractProxy proxy = new MyContractProxy();
proxy.MyMethod();
proxy.MyMethod();
proxy.Close();

Output :
MyService.MyService()
Counter = 1
Counter = 2
MyService.Dispose()

Singleton Service and Client :

Singleton Service Code :

Service Code :
[ServiceContract(Session=true)]
interface IMyContract
{
[OperationContract]
void MyMethod();
}

[ServiceContract]
interface IMyOtherContract
{
[OperationContract]
void MyOtherMethod();
}

[ServiceBehavior(InstanceContextMode=InstanceContextMode.Single)]
class MySingleton : IMyContract, IMyOtherContract, IDisposable
{
int m_Counter = 0;
public MySingleton()
{
Trace.WriteLine(“MyService.MyService()”);
}
public void MyMethod()
{
m_Counter++;
Trace.WriteLine(“Counter = ” + m_Counter);
}
public void MyOtherMethod()
{
m_Counter++;
Trace.WriteLine(“Counter = ” + m_Counter);
}
public void Dispose()
{
Trace.WriteLine(“MyService.Dispose()”);
}
}

Client Code :
MyContractProxy proxy1 = new MyContractProxy();
proxy1.MyMethod();
proxy1.Close();

MyOtherContractProxy proxy2 = new MyOtherContractProxy();
proxy2.MyOtherMethod();
proxy2.Close();

Output :
MyService.MyService()
Counter = 1
Counter = 2