What is the easiest way to save a LINQ query for later use?

Question

I have a request for a feature to be able to save a user's search for later.

Right now I'm building LINQ statements on the fly based on what the user has specified.

So I started wondering, is there an easy way for me to simply take the query that the user built, and persist it somewhere, preferably my database, so that I can retrieve it later?

Is there some way of persisting the query as XML or perhaps JSON, and then reconstituting the query later?

Answer 1

Take a look at the Expression class. This will allow you to pre-compile a query. Although persisting this for later use to the DB for better performance is questionable.

Answer 2

Never done this before, but I've had this idea:

Rather than having the query run against your database directly, if you were to have it run against an OData endpoint, you could conceivably extract the URL that is generated as the query string, and save that URL for later use. Since OData has a well-though-out spec already, you would be able to profit from other people's labor.

Answer 3

I'd go with a domain-specific object here even if such goodies did exist -- what happens when you save serialized queries in LINQ and your underlying model changes, invalidating everyone's saved queries. Using your own data format should shield you from this to some extent.

Answer 4

I'm writing this as I watch this presentation at PDC10. Just after the 1-hour mark, he shows how he's built a JSON serializer for expression trees. You might find that interesting.