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OData for LightSwitch

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Microsoft is continuing its plan to make OData as ubiquitous as web services. Their latest offering allows LightSwitch 2 to both produce and consume OData services.

LightSwitch is a rapid application development platform based on .NET with an emphasis on self-service. Based around the concept of the “citizen programmer”, Visual Studio LightSwitch is intended to allow for sophisticated end users to build their own business applications without the assistance of an IT department. So why should a normal office worker knocking out a CRUD application care about OData?

OData brings something to the table that neither REST nor Web Services offer: a standardized API. While proxy generation tools can format WS requests and parse the results, they don’t offer any way of actually hooking the service into the application. Instead developers have to painstakingly map the calls and results into the correct format. And REST is an even lower on the stack than that, usually offering only raw XML or JSON.

By contrast, every OData API looks just like any other OData API. The requests are always made the same way through the same conventions; the only significant difference is the columns being returned. This allows tools like LightSwitch to work with OData much in the same way it works with database drivers. In fact, consuming a OData service from LightSwitch is done using the same Attach Data Source wizard used for databases.

To expose OData from LightSwitch one simply needs to deploy the application in one of the three-tier configurations. From there you can consume the OData service from not only LightSwitch but also any other OData enabled application. Beth Massi’s example show importing LightSwitch data into Excel using the PowerPivot extension.

Another new feature in LightSwitch is the ability to redefine relationships between tables that come from external data sources. John Stallo writes,

One of the most popular requests we received was the ability to allow data relationships to be defined within the same data container (just like you can add relationships across data sources today). It turns out that there are quite a few databases out there that don’t define relationships in their schema – instead, a conceptual relationship is implied via data in the tables. This was problematic for folks connecting LightSwitch to these databases because while a good number of defaults and app patterns are taken care for you when relationships are detected, LightSwitch was limited to only keying off of relationships pre-defined in the database. Folks wanted the ability to augment the data model with their own relationships so that LightSwitch can use a richer set of information to generate more app functionality. Well, problem solved – you can now specify your own user-defined relationships between entities within the same container after importing them into your project.

LightSwitch offers a “Metro-inspired Theme” but at this time it doesn’t actually build Windows 8 or Windows Phone Metro-style applications. It does, however, offer options for hosting LightSwitch applications on Windows Azure.

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