What is better? Or maybe - is the following a good practice? I use Spring.net to create an instance of DbContext and then inject it into every controller for use in actions. The object is a singleton. Sometimes I get an exception which says that the "The ObjectContext instance has been disposed.." I suspect that this might be the reason, however this is not repeatable, and so far my application is only used by me during the development.
Now, would it be better to create a DbContext in every controller class and reuse in it's actions; or maybe create the DbContext object in every action itself; or just set it in the Spring config not to be a singleton, so it is created every time it is being accessed?
It is best to inject your dbcontext using request scope. That way, the context is created on the start of a request and disposed at the end. During the request you'll have a db context available so that it can handle lazy loaded objects for you.
When you register as a singleton, the dbcontext is shared for all requests, which most of the time isn't what you want. For instance, it might be that it hold a reference to all your loaded objects, potentially loading the entire db into memory.