What are behaviors in WCF and how do you use them?

Question

ICSM Computer · Answer

Behaviors in WCF are extensibility points that allow you to customize or extend the way WCF services, endpoints, operations, or clients behave at runtime.
They don't change the message data, but they can influence execution,
security, validation, instance management, error handling,
logging, etc.
Types of WCF Behaviors
Behavior Type
Applied To
Interface
Purpose
Service behavior
Service-wide
IServiceBehavior
Control service instance, concurrency, error handling, etc.
Endpoint behavior
A single endpoint
IEndpointBehavior
Modify client or service endpoints
Operation behavior
A method
IOperationBehavior
Control parameter handling, serialization
Contract behavior
Interface level
IContractBehavior
Modify all operations in a contract
Client behavior
Client proxy
IEndpointBehavior
Customize how a client behaves
Example: Service Behavior for Logging
1. Implement a custom behavior
public class LoggingBehavior : IServiceBehavior
{
    public void ApplyDispatchBehavior(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)
    {
        foreach (ChannelDispatcher cd in serviceHostBase.ChannelDispatchers)
        {
            foreach (EndpointDispatcher ed in cd.Endpoints)
            {
                ed.DispatchRuntime.MessageInspectors.Add(new LoggingMessageInspector());
            }
        }
    }
    public void AddBindingParameters(...) { }
    public void Validate(...) { }
}
2. Implement the message inspector
public class LoggingMessageInspector : IDispatchMessageInspector
{
    public object AfterReceiveRequest(ref Message request, IClientChannel channel, InstanceContext instanceContext)
    {
        Console.WriteLine("Request received: " + request.ToString());
        return null;
    }
    public void BeforeSendReply(ref Message reply, object correlationState)
    {
        Console.WriteLine("Reply sent: " + reply.ToString());
    }
}
3. Add Behavior to Service Host (programmatically)
ServiceHost host = new ServiceHost(typeof(MyService));
host.Description.Behaviors.Add(new LoggingBehavior());
host.Open();
4. Or Add Behavior via Config
You must also create a BehaviorExtensionElement and register it in
web.config to load it via configuration — this is more advanced but allows reuse.
Built-in Behaviors Examples
Built-in Behavior
Purpose
ServiceMetadataBehavior
Enables metadata exchange (WSDL)
ServiceDebugBehavior
Includes exception details in faults
ServiceThrottlingBehavior
Controls concurrency, sessions, and calls
ServiceAuthorizationBehavior
Controls access control
ClientViaBehavior
Controls how clients indicate their URI
Summary
Behaviors are plug-in points that control how WCF runs.You implement the correct interface (IServiceBehavior, IEndpointBehavior, etc.)You can apply them programmatically or via configuration.Useful for cross-cutting concerns: logging, error handling, validation, etc.

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What are behaviors in WCF and how do you use them?

ICSM Computer

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1 Answers

Types of WCF Behaviors

Example: Service Behavior for Logging

1. Implement a custom behavior

2. Implement the message inspector

3. Add Behavior to Service Host (programmatically)

4. Or Add Behavior via Config

Built-in Behaviors Examples

Summary

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Behavior Type	Applied To	Interface	Purpose
Service behavior	Service-wide	`IServiceBehavior`	Control service instance, concurrency, error handling, etc.
Endpoint behavior	A single endpoint	`IEndpointBehavior`	Modify client or service endpoints
Operation behavior	A method	`IOperationBehavior`	Control parameter handling, serialization
Contract behavior	Interface level	`IContractBehavior`	Modify all operations in a contract
Client behavior	Client proxy	`IEndpointBehavior`	Customize how a client behaves

Built-in Behavior	Purpose
`ServiceMetadataBehavior`	Enables metadata exchange (WSDL)
`ServiceDebugBehavior`	Includes exception details in faults
`ServiceThrottlingBehavior`	Controls concurrency, sessions, and calls
`ServiceAuthorizationBehavior`	Controls access control
`ClientViaBehavior`	Controls how clients indicate their URI