Entity Framework 4 and caching of query results

Question

Say I have a table or 2 that contains data that will never or rarely change, is there any point of trying to cache those data? Or will the EF context cache that data for me when I load them the first time? I was thinking of loading all the data from those tables and use a static list or something to keep that data in memory and query the in memory data instead of the tables whenever I need the data within the same context. Those tables I speak of contains typically a few hundred rows of data.

Answer 1

You can check EF caching provider but be aware that caching in this way is performed strictly on query basis - so you must use the same query all the time to get cached data. If you use another query it will first be executed to be considered as cached and then you use it again to hit the cache. If you want to avoid this and cache data with ability to run any query on cached collection you must roll on your own solution (simply load data to list and keep it somewhere). When you load entities to cached list make sure that you turn off proxy creation (lazy loading and change tracking).

Caching per context instance really works but using context itself as a cache is pretty bad choice - in most scenarios I would call it EF anti-pattern. Use context as unit of work = do not reuse context for multiple logical operations.

Answer 2

you'll have to roll your own for any ef4 linq queries, as they are always resolved to sql, and thus will always hit the db. a simple cache for your couple tables probably wouldn't be hard to write.

if you're going to be querying by id though, you can use the ObjectContext.GetObjectByKey method, and it will look in the object cache before querying the db.

Answer 3

The EF context will cache "per instance". That is, each instance of the DbContext keeps it's own independent cache of objects. You can store the resulting list of objects in a static list and query it all you like without returning to the database. To be safe, make sure you abandon the DbContext after you execute the query.

var dbContext = new YourDbContext();
StaticData.CachedListOfThings = dbContext.ListOfThings.ToList();

You can later use LINQ to query the static list.

var widgets = StaticData.CachedListOfThing.Where(thing => thing.Widget == "Foo");

The query executes the in-memory collection, not the database.