Douglas Purdy

The (WCF) Data Services team just released the an update to .NET FX 3.5 for the OData.

New features in this release are:

· Projections: This ADO.NET Data Services URI format has been extended to express projections (i.e. you can now work with a subset of the properties of an entity).  This release includes both server and client library (including LINQ support) support for projections.  We’ve done a fair amount of work in this space to support roundtripping projected values, working with anonymous types, etc.  We’ll create a subsequent series of posts to describe this feature.

· Data Binding:  The data services client library for the .NET Framework 3.5 SP1 has been extended to support two-way data binding.

· Row Count: One scenario we heard a ton of feedback on after shipping V1 of ADO.NET Data Services in the .NET Framework 3.5SP1 is the ability for the a client of a data service to determine the total number of entities in a set without having to retrieve them all.  To address this need, we have extended the data services addressing scheme to allow a client to obtain this type of information without having to download all the entities in a set.

· Feed Customization (aka “Web Friendly Feeds”): A common ask we have received is to provide the ability to customize how entities are mapped into the various elements of an AtomPub feed.  This feature does just that by providing a data service author declarative control over how the data service runtime maps the properties of an entity (e.g. a Customer, Order, etc) to the elements of a feed.

· Server Driven Paging (SDP): This one is best described by example.  If you had a data service that exposes photos, you likely want to limit the total number of photos a single request to the service can retrieve because the total collection of photos may be very large.  This feature allows a service author to set per collection limits on the total number of entities returned for each request.  In addition to limiting the number of photos returned per request, the server provides the client a “next link” which is simply a URI specifying how to continue retrieving the rest of the entities in the collection not returned by the first request.  For those familiar with AtomPub, this feature adds support for AtomPub <link rel=”next” …> elements to the data service runtime.

· Enhanced BLOB Support: This feature enhances the BLOB support provided in V1 to enable data services to stream arbitrarily large BLOBs, store binary content separate from its metadata, easily defer the loading of BLOB content when its metadata is requested, etc.

· Request Pipeline: We have started to expose events throughout the data services server request processing pipeline.  For this release we’ll expose request level events and in future we’ll look to expose more fine grained events based on your feedback.  The goal of exposing our processing pipeline is to allow services further transparency into a data service such that a service author can do things such as setting HTTP response cache headers, wrapping interceptor processing and data service request processing in a single transaction, etc.

· New “Data Service Provider” Interfaces for Custom Provider Writers: As the data services runtime has evolved, so has the number of ways people want to plug data into the data service framework.  In V1, two methods (Entity Framework and arbitrary .NET classes) were supported to enable a data service to interact with various diverse data sources.  To address another class of environments and data sources we have introduced a way to write a “custom” provider for those cases when the previous two provider models don’t meet your needs.