Singleton pattern in wcf

Question

Is it advisable to use singleton pattern in wcf application?. I have ServiceResponse class which will take care the response and errordetail and almost all the details of the wcf current request. When i first hit the service, lets say i have 5 properties in ServiceResponse class and which got filled with respective values and some error details in errordetail property. For the next hit, lets say i dont get any error details and all other 4 properties got filled up.

But the thing here is, the errordetail property is still populated with the previous values which i assume the singleton object doesnt get created even after the subsequent hits. So only changed values got affected but untouched property still holds the previous value for the subsequent hits.

is it because the appdomain never get unloaded to release the object to allow the next sinleton object to get created for the other imm. request? How to acheive the singleton pattern in wcf otherwise. Appreciate the help.

Answer 1

The singleton pattern implies that the object is only instantiated once and lives for the entire lifetime of the AppDomain. You should not store data that is specific to a given request in static objects because all of them will share the same data which might not be what you are looking for.

Whether it is a good idea or not to use static objects in a WCF application is a question that will entirely depend on your scenario and what you need to store there. Since WCF is a multithreaded environment where multiple threads could access this shared data you will have to take special care to ensure that this data is thread safe by using the proper synchronization mechanisms.

is it because the appdomain never get unloaded to release the object to allow the next sinleton object to get created for the other imm. request?

There's a single AppDomain that gets created when your application starts. Don't expect to get a different AppDomain on each request. Requests will all be served from the same AppDomain until the application gets recycled by IIS.