PerSession Instance Management - (WCF)

In WCF (Windows Communication Foundation), instance management is the process of creating and managing service instances. PerSession instance management is one of the four instance management modes in WCF that allows the service to maintain a separate instance of itself for each client session.

Syntax

To implement PerSession instance management in WCF, you will need to specify the InstanceContextMode and ConcurrencyMode settings in the service contract. Here's an example:

[ServiceContract(SessionMode = SessionMode.Required)]
public interface IMyService
{
  [OperationContract]
  string GetMessage();
}

[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession, ConcurrencyMode = ConcurrencyMode.Single)]
public class MyService : IMyService
{
  private int _counter = 0;

  public string GetMessage()
  {
    _counter++;
    return "Hello, client! You are connected to session " + OperationContext.Current.SessionId + ", and this is message " + _counter;
  }
}

Example

Here's an example of how to implement PerSession instance management in WCF using the above service contract:

// Set up the WCF service
ServiceHost host = new ServiceHost(typeof(MyService));

// Start the WCF service
host.Open();

// Connect to the WCF service
ChannelFactory<IMyService> factory = new ChannelFactory<IMyService>(new BasicHttpBinding(), "http://localhost:8000/MyService");
IMyService service = factory.CreateChannel();

// Call the WCF service multiple times to demonstrate PerSession instance management
Console.WriteLine("Calling service for the first time...");
Console.WriteLine(service.GetMessage());

Console.WriteLine("Calling service for the second time...");
Console.WriteLine(service.GetMessage());

Console.WriteLine("Calling service for the third time...");
Console.WriteLine(service.GetMessage());

// Close the WCF service
host.Close();

Output

When you run the code to test the WCF service with PerSession instance management, you should see output that looks something like this:

Calling service for the first time...
Hello, client! You are connected to session 78e50e94-deea-4880-a2b6-7efeb20257cb, and this is message 1
Calling service for the second time...
Hello, client! You are connected to session 78e50e94-deea-4880-a2b6-7efeb20257cb, and this is message 2
Calling service for the third time...
Hello, client! You are connected to session 78e50e94-deea-4880-a2b6-7efeb20257cb, and this is message 3

Explanation

In the example code, we define a service contract (IMyService) that includes a method (GetMessage) that returns a string. We then define a service class (MyService) that implements the service contract and maintains a counter to track how many times the method has been called. In the service class, we use the InstanceContextMode.PerSession setting to ensure that each client session gets its own instance of the service, and the ConcurrencyMode.Single setting to ensure that only one thread can access the service at a time.

In the test code, we set up and start a WCF service host, connect to the host, and call the GetMessage method multiple times to demonstrate that each client session gets its own instance of the service. We then close the WCF service host.

Use

PerSession instance management is useful in WCF applications where you need to maintain separate service instances for each client session. This mode is appropriate for applications that maintain state between calls, such as in calculations or database operations, which require the service instance to continue processing data.

Important Points

• PerSession instance management mode in WCF maintains separate service instances for each client session.
• PerSession instance management mode is useful for applications that maintain state between calls.
• PerSession instance management, and the other instance management modes available in WCF, can be set using the InstanceContextMode and ConcurrencyMode settings in the service contract.

Summary

In this page, we discussed PerSession instance management in WCF, including the syntax, example, output, explanation, use, and important points. Using PerSession instance management, you can maintain separate instances of a WCF service for each client session, making it possible to manage state and track client-dependent information during service operations.