Marcelo's WebLog : ADO.NET Data Services

Download Data Services Update for .NET 3.5 SP1

marcelolr — Thu, 17 Dec 2009 22:00:00 GMT

Yesterday the availability announcement went up on the team blog, so why wait? Get yourself some updated bits and start data binding, blob'ing, paging, projecting, and counting entities, all from within the comfort of your programming chair!

If you haven't already, now is a great time to subscribe to the feed on the team blog. New content to help you make the most of the update will be posted regularly now that the release is out.

Enjoy!

HTTP 403.9 with ADO.NET Data Services

marcelolr — Wed, 09 Dec 2009 22:00:00 GMT

If the error HTTP 403.9 may comes up when making multiple requests to an ADO.NET Data Service, the first thing to check is the operating system the server is running on. Windows XP and other client operating systems have a limit on the number of simultaneous connections that are supported.

The KB Error Message: HTTP 403.9 - Access Forbidden: Too many users are connected describes this situation in terms of Windows 2000 Professional, but this applies to other client systems as well.

Enjoy!

Vistual Studio visualizer for OData

marcelolr — Thu, 19 Nov 2009 22:00:00 GMT

Fabian Winternitz is one of our awesome tools developers, and you can see some of his work in this post. That's a Visual Studio extension that will display searchable diagrams for the model exposed by any service endpoint that exposes OData metadata. Which these days includes a lot of software.

Personally, I think it's great to see on one hand the level of support for the ecosystem, and on the other hand the balance of power, expressiveness and simplicity that OData provides. Back when everything started in the early days of Project "Astoria", I don't think anyone had any idea as to how broad a spectrum of software components would play in this space, but it looks like sticking to simplicity and proven standards paid off.

Enjoy!

WCF Data Services

marcelolr — Wed, 18 Nov 2009 22:00:00 GMT

Over at the team blog, you can find this post about ADO.NET Data Services changing its name to WCF Data Services in the .NET Framework 4 time frame. This is goodness by every account - over time, this just means a more integrated experience when developing for these stacks, with less seams and caveats.

Enjoy! - in anticipation if nothing else :)

ADO.NET Data Services - CTP and more

marcelolr — Thu, 03 Sep 2009 00:00:00 GMT

In case you haven't seen this yet, the CTP release has been announced at http://blogs.msdn.com/astoriateam/archive/2009/08/31/ado-net-data-services-v1-5-ctp2-now-available-for-download.aspx.

Following the philosophy that folks like tables, here you go.

Feature	Available in CTP1?	New in CTP2
Projections	No	Yes!
Data Binding	Yes	API cleanup for types
Row Count	Yes	Bug fixes
Feed Customization	Yes	Renamed attributes and more flexibility
Server Driven Paging	Yes	Client library support
Enhanced BLOB support	Yes	Client library support
Request Pipeline	No	Yes!
New Provider Interface	Yes	API refactoring

You probably want to keep checking the blog, as there are some posts coming that will dive deeper into some of the new features.

Enjoy!

ADO.NET Data Services and PHP

marcelolr — Sat, 22 Aug 2009 00:00:00 GMT

Data, data, data everywhere... Go ahead and click - code samples ahead.

http://blogs.msdn.com/interoperability/archive/2009/08/21/a-new-bridge-for-php-developers-to-net-through-rest-php-toolkit-for-ado-net-data-services.aspx

Enjoy!

ADO.NET Data Services Cheat Sheet

marcelolr — Sat, 01 Aug 2009 00:00:00 GMT

Just run into this today - very nifty cheat sheet for ADO.NET Data Services.

http://www.sadev.co.za/files/Posters/ADO.NET%20Data%20Services%20Cheat%20Sheet.pdf

ADO.NET Data Services v1.5 CTP1 released

marcelolr — Thu, 19 Mar 2009 00:00:00 GMT

The announcement is available here. There's a video showing how to get started, a FAQ, and a link to give feedback and ask questions, so no need to wait - you can play with the future today!

Project Codename "Astoria Offline", Alpha Preview

marcelolr — Wed, 11 Mar 2009 00:00:00 GMT

As recently announced, early preview bits are available for Astoria that provide synchronization capabilities, which allow you to create applications that work offline (among other things).

Note that this announcement was made close to the "1.5" made not too long ago, but they are separate, distinct things that will not play well if installed on the same machine. You really, really don't want to mix the two.

The idea here is really to reach out, give people a feeling of what the problem space looks like and what a solution might look like, and help us get feedback and have a conversation around this. As usual, the team blog and the forums are your best friends.

Enjoy!

ADO.NET Data Services v1.5 CTP announced

marcelolr — Wed, 04 Mar 2009 01:00:00 GMT

If you haven't seen this yet, ADO.NET Data Services is announcing an upcoming CTP for the v1.5 functionality over here.

And if you're wondering about what "1.5" means, yes, that's explained in the post.

Some of the goodies that we've wanted for are in: row count, data binding on the client, "friendly feeds" (ie, have the feeds actually have useful values in title and such), paging, and more.

The release date for the CTP hasn't been announced (not at the time I'm writing this in any case), but stay tuned!

A plea for ADO.NET Data Services black belt

marcelolr — Tue, 17 Feb 2009 01:00:00 GMT

Phani, master and commander of all things Astoria, has in his posession pictures of the latest ski trip... (yes, the team definitely knows how to have fun)

This is just my way of publicly calling unto him to post them. Peer pressure in action!

ADO.NET Data Servces in action (and in Word and Outlook!)

marcelolr — Sat, 14 Feb 2009 01:00:00 GMT

Beth Massi has written a couple of very good posts involving ADO.NET Data Services, which I strongly encourage folks to read.

Using ADO.NET Data Services (the fundamentals, great walk-through)
Building an Office Business Application for TechReady 8 (awesome teaser)
OBA Part 2 - Building an Outlook Client against LOB Data (integrating with Outlook is much easier than I thought!)
OBA Part 3 - Storing and Reading Data in Word Documents (OpenXML, LINQ to XML, schema inference in VS, Astoria updates, VB XML literals... what more could I ask for?)

Can't wait to see what she comes up with next...

Depth vs. width in ADO.NET Data Services $expand

marcelolr — Tue, 02 Dec 2008 01:00:00 GMT

The $expand option in the query filter is used to request entities associated with the last segment of a request. This is often used to ensure that entities can be materialized with their relationships wired together and to reduce the number of roundtrips to the server.

For example, if http://www.example.com/service.svc/Customers returns all customers, then http://www.example.com/service.svc/Customers?$expand=Orders could be used to return all customers with all their Orders, assuming customers have an Orders collection.

You can use request multiple references and collections to be exapnded. One gotcha about the $expand syntax is that there is a different syntax for "drilling" through references: the forward slash is used to indicate drilling in, while a comma is used to separate the parallel expansion paths.

Here are some examples that will hopefully clarify this (omitting the path to the service).

/Customers?$expand=Orders. Returns customers and the orders of the customers.
/Customers?$expand=Orders,Preferences. Returns customers and the preferences of the customers.
/Customers?$expand=Orders,Orders/OrderDetails,Preferences. Returns customers, the orders of the customers, the order details of the orders of the customers, and the preferences of the customers.
/Customers?$expand=Orders/OrderDetails,Preferences. Same as the last one - when you go deep, all the parents are implied, so Orders/OrderDetailsOrders.
/Customers?$expand=Orders/OrderDetails,Orders/ShippingInfo. Returns customers, the orders of the customers, the order details of the orders of the customers, and the shipping informatio of the orders of the customers. Note that the ',' is used to separate paths starting from the last segment (Customers), so if you want to expand properties in parallel from a deeper entity, you need to specify the path again, as in this example.

Hope this was helpful - please post comments if you have further questions!

Limiting how many entities are returned from an ADO.NET Data Service

marcelolr — Thu, 20 Nov 2008 01:00:00 GMT

If you want to limit the number of entities returned from a service, you have a few alternatives...

If you're writing code for the client, the easiest way is to just use the '$top' clause to limit how many entities will be returned. Note that '$top' doesn't account for entities you expand using '$expand', so be careful with what you expand if you're using it.

That pretty much covers it for the options on the client - the server however is a more interesting thing.

First, you have the configuration options. MaxResultsPerCollection allows you to limit not only the number of entities returned at the top level of a request, but also at each collection within, so clients can't use '$expand' to overwhelm the server. Because a batch request can have multiple queries, you can combine that with MaxBatchCount.

The problem with using the configuration on the server is that it's meant more as a security feature than as a general paging mechanism, and as such the responses returned will (a) likely cause the client to error, because the response ends mid-stream, and (b) the client will have no good way to "continue" asking for data from where the last request left off.

A better approach might be to ask clients to be explicit about how many entities they're willing to handle at once using the '$top' option, and overriding the OnStartProcessingRequest method on the data service to check that the URL has indeed specified the '$top' option. Of course, you still want to set the configuration to safeguard your server!

Enjoy!

Filter not working in ADO.NET Data Services?

marcelolr — Wed, 19 Nov 2008 01:00:00 GMT

I know this probably sounds kind of silly for a blog post, but:

9 times out of 10, if your ADO.NET filter isn't changing the results you get back, make sure you are using "path?$filter=f" rather than "path?filter=f".

Turns out that without the '$' prefix, ADO.NET Data Services won't recognize the filter command. I'm sure I've discussed this in the past, but I can't find the reference, so let me replay it here.

Query parameters prefixed with '$' are reserved for system use (try it!). Everything else is for the service author to that whatever is desired.

Typically we'll map these "bare" parameters to service operation parameters, but if they don't map to anything, we'll just let them be.This allows you (or some other plug-in in your web server) to pass a session ID or any other desired information in the query portion of the URL.