Enterprise Library Call Handlers

Call Handlers are Enterprise Library's extension mechanism. They allow code to be injected before or after a method is called. Enterprise Library, as of version 4.1, comes with the following call handlers and associated handler attributes, in assembly Microsoft.Practices.EnterpriseLibrary.PolicyInjection.CallHandlers:

• AuthorizationCallHandler / AuthorizationCallHandlerAttribute
• CachingCallHandler / CachingCallHandlerAttribute
• ExceptionCallHandler / ExceptionCallHandlerAttribute
• LogCallHandler / LogCallHandlerAttribute
• PerformanceCounterCallHandler / PerformanceCounterCallHandlerAttribute
• ValidationCallHandler / ValidationCallHandlerAttribute

If you know the Enterprise Library, you can easily guess their meaning from their names.

I have written two additional call handlers:

• TransactionCallHandlerAttribute (implements ICallHandler): wraps the target method in a transaction scope
• TriesCallHandlerAttribute (implements ICallHandler): tries to invoke the target method a number of times, while an exception is thrown

For simplicity's sake, I have implemented ICallHandler in the attribute class, so the ICallHandler.CreateHandler method only returns this.

Usage is like this:

[TransactionCallHandler(TransactionScopeOption.Required)]

void SomeMethod();

and

[TriesCallHandler(3, Delay = 500)]

void SomeOtherMethod();

Enjoy!