什么时候asp.net角色提供者生存和死亡？

I am working with a custom role provider in asp.net and it appears that once the provider is loaded into memory, it doesn't drop out of memory until the web application is restarted (like when the web.config file is changed and saved). Further, all of the requests to that web application seem to utilize the one instance of the role provider.I am working with a custom role provider in asp