Services
Technology Web App Development Mobile App Development Windows App Development Database Development UI/UX Development Cloud Development SEO Digital Marketing Guest Posting Content Writing Artificial Intelligence Data Science ERP Development CRM Development CMS Development LMS Development Business Listing Blockchain Technology Startup Promotion
Products
Data Converter Cleaner TUC - Unit Converter Import Export Survey Manager Tweet Controller
Developer
Article Blog Forum Interview Beginner News Startup Quiz
Users
Career
Apply Job Internship
Pricing
Login Sign Up Get a Quote

interview

home / developersection / interviews / what are the different instance management modes available in wcf?
Ask Question

What are the different instance management modes available in WCF?

Ravi Vishwakarma 554 27 May 2025
c# c#wcf
Updated 27 May 2025
Ravi Vishwakarma
Ravi Vishwakarma

IT-Hardware & Networking

Ravi Vishwakarma is a dedicated Software Developer with a passion for crafting efficient and innovative solutions. With a keen eye for detail and years of experience, he excels in developing robust software systems that meet client needs. His expertise spans across multiple programming languages and technologies, making him a valuable asset in any software development project.

Message

1 Answers

Ravi Vishwakarma
Ravi Vishwakarma 27 May 2025
Report Abuse

In WCF (Windows Communication Foundation), instance management defines how service objects are created and maintained for client requests. WCF provides three main instance context modes, configured using the [ServiceBehavior] attribute's InstanceContextMode property.

1. PerCall (default)

  • A new service instance is created for each client request.
  • No state is maintained between calls.
  • Ideal for stateless services.
[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall)]
public class MyService : IMyService
{
    // A new instance is created per request
}
  1. Pros:
    1. High scalability.
    2. No need for synchronization.
    3. Low memory usage.
  2. Cons:
    1. Cannot maintain service-level state.

2. PerSession

  • One service instance is created per client session (requires session-enabled binding like NetTcpBinding or WSHttpBinding with reliable session).
  • State is preserved throughout the session.
[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession)]
public class MyService : IMyService
{
    // Maintains state per client session
}
  1. Pros:
    1. Maintains state for a specific client.
    2. Useful for multi-call workflows.
  2. Cons:
    1. Increased memory per client.
    2. Requires bindings that support sessions.

3. Single (Singleton)

  • A single service instance serves all client requests.
  • Shared state across all clients.
[ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)]
public class MyService : IMyService
{
    // Shared instance for all clients
}
  1. Pros:
    1. Easy to maintain shared state.
    2. Suitable for centralized services.
  2. Cons:
    1. Must handle concurrency (ConcurrencyMode.Multiple or Reentrant).
    2. Potential bottleneck if not managed correctly.

Summary Table

Mode Instance per State Preservation Concurrency Consideration
PerCall Call No Not needed
PerSession Session Yes (per client) Needed if multiple calls overlap
Single Application Yes (shared) Must handle explicitly

You can configure it like this:

[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession)]
public class MyService : IMyService
{
    // Implementation
}
MindStick Training