Playing with OData

OData is the bomb.

I just spent a few days creating a quick ASP.NET MVC3 website for a client. Nothing fancy, and thanks to MVC’s scaffolding the job was done quickly enough. Then the client asked me to create a web service so that another one of their systems could access it in the future.

Hi Matt,
Need you to write a simple API that allows us to query the job bag DB with an Job Number and return back the Client Ref (if available). Ideally – if you can extend out the API to return all data for a record we can use this for other things in the future also.

Come talk if you need more than this back of fag packet spec :)

Well, with 6 lines of code it was done. Right-click Web project, Add New Item, WCF Data Service.

public class JobService : DataService<JobSystemEntities>
{
    // This method is called only once to initialize service-wide policies.
    public static void InitializeService(DataServiceConfiguration config)
    {
        config.SetEntitySetPageSize("*", 50); // limit to 50 rows

        config.SetEntitySetAccessRule("Jobs", EntitySetRights.AllRead); // allow querying of all jobs e.g. http://localhost:34031/JobService.svc/Jobs            
        // config.SetEntitySetAccessRule("Jobs", EntitySetRights.ReadSingle); // need to specify a job e.g. http://localhost:34031/JobService.svc/Jobs(1001)

        config.SetEntitySetAccessRule("Clients", EntitySetRights.AllRead);
        config.SetEntitySetAccessRule("Departments", EntitySetRights.AllRead);
        config.SetEntitySetAccessRule("JobTypes", EntitySetRights.AllRead);

        config.DataServiceBehavior.MaxProtocolVersion = DataServiceProtocolVersion.V2;
    }

I used Jeff and Tim’s PDC10 screencast (which I linked to a few posts ago) as a reference on how to do this. (They add the OData service 45 mins in).

Too easy. Using that we can do all sorts of awesome queries, like:

  • Query a specific job – 1001: http://localhost/Jobs.svc/Jobs(1001)
  • View all the Clients: http://localhost/jobs.svc/Clients
  • What are all the Job Types? : http://localhost/jobs.svc/JobTypes
  • “Give me all jobs that have a ClientCode of 12345″: http://localhost/Jobs.svc/Jobs?$filter=ClientCode eq ’12345′
  • Or how about “give me all of Client 1′s jobs” : http://localhost/Jobs.svc/Clients(1)/Jobs
  • Here’s a great OData cheat sheet which explains the above syntax, by Microsoft’s Alex James.

    Authentication

    The only trouble is, this service is visible to the whole wide internet. But Alex James comes to the rescue again, with this great article on how to use forms authentication with a WCF Data Service. After following his instructions, I created a quick Winforms app to test that it would work using web forms authentication and yep, no problems.

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2 thoughts on “Playing with OData

  1. Hi MAtt,
    That was a nice article.
    What I cannot figure out is where in the MVC 3 code you instantiate the
    DataServiceContext class and the proxy objects generated by the reference to the wcf data service.
    Could you please provide a simple demo?
    Cheers
    Cleyton

  2. Hi,

    Odata url is being used for mobile. how to give them permission to update the data. they can read the data using the WCF data service url but update is not happening. second how to give login permission to them?

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