Does it make sense for an ASP.NET Web API method to return IQueryable<T>?
asp.net-web-api, deferred-execution, iqueryable
Solution
Responses to methods returning `IQueryable<T>` can be "queried" by passing some odata-like parameters in the query string ($top, $skip, $filter, $orderby). For example, if your resource can be found at .../api/People, you can send those requests, which will cause the server to return different data:
.../api/People?$top=10 ==> return only the first 10 elements
.../api/People?$skip=10&$top=5 ==> return the 11th to 15th elements
.../api/People?$filter=Name%20eq%20'John' ==> Only return people named "John"
.../api/People?$orderby=Name&$top=10 ==> return the first 10 elements, ordered by name
Notice that on the beta release any operation which returns `IQueryable<T>` automatically has this "querying" support added to it. On the latest bits (from codeplex), you need to manually add a `[Queryable]` attribute to the operation to enable this behavior.
If you don't want that querying behavior, then yes, returning `IEnumerable<T>` is just fine.
Problem
I'm working on a project that uses the new Web API and I noticed somebody is returning an IQueryable<T> from a Get method. My understanding is that IQueryable is useful for improving performance (deferred execution), but I don't think a client on the other end of an HTTP connection is going to be able to take advantage of that. My gut is telling me that this should be IEnumberable<T>instead. Am I right about this?