Remove all references to a DLL across all application domains

Question

I have a web application that dynamically loads assemblies based on database configuration entries to perform certain actions (dynamic plugin style architecture).

The calls to the objects are in a Factory Pattern implementation, and the object is cached (in a static dictionary<> within the Factory) as the calls can be made many thousands of times in a minute.

The calls to this factory are made from both the main web application and a number of webservices, some in different assemblies/projects.

When I need to update one of these DLLs, I have to recycle IIS to get the DLL released.

As this has an impact on another application on the server, I wanted to know if there was a way I could release the DLL without restarting IIS?

Answer 1

There's absolutely no way to unload a loaded assembly other than killing the AppDomain which is basically what you are doing when you restart IIS.

Answer 2

You can try restarting the application pool not the whole IIS server. Maybe that will do the trick for you

Answer 3

If you have an assembly that you need to load and unload you will have to jump through a few hoops.

• the types being loaded must derive from MarshalByRefObject
• the types being loaded must derive from an interface that will be used to call them
• you must build a remoting based 'loader' to isolate the loaded assembly in a new appdomain, which can be unloaded.

see http://www.west-wind.com/presentations/dynamicCode/DynamicCode.htm for a good introduction. It is a bit dated and deals with dynamically generated code but given your rep I would assume that you can extract the relevant information.