Azure OData Service

What is OData?

SOAP based Web Service are a medium for applications to communicate between each other and RESTful APIs released after to make these communications easier. OData stood as the next step. It stands for Open Data Protocol. The general philosophy carried by OData is standardization of the usage of RESTful API, and empowering applications to make this usage a simpler affair. 

Basically, through the OData protocol, you are able access any particular bit of data in the target system, via an HTTP URL. 

How do I expose my application data, as an OData URL?

So, Salesforce can consume data via the OData protocol. But how would you expose your back-office data as an OData service in the first place?

Where do I find test OData Services?

 

If you would like to stand out, by creating situation specific data, a personal-looking OData URL, or simply to get a feel of creating a custom OData service.

Creating an OData Service

Like I said, one of the ways to create an OData service is through the .Net WCS Data Services templates. That is what we would be using here.

Creating a Cloud Database

To create an OData service, there should be some data to read from in the first place. Let’s leverage the Microsoft Azure platform for making a hosted SQL database. 

Building an OData Service 

Let us now proceed to build an OData service that can read from this cloud data base. We are going to use the WCF Data Service template available in the Visual Studio. Ofcourse you can use earlier versions of Visual Studio, but then you might need to go through some extra steps to enable the WCF Data Services template. Described below are the steps to create the OData Service. 

Open Visual Studio, click File > New Project, and choose ASP .NET Web Application. Provide a meaningful Project Name and Solution Name. Click OK.
In the pop up that is presented, choose “Empty”, as we do not require any pre-built templates at this point.
This would make Visual Studio set up a project and solution space for you. It is good to have the Solution Explorer view enabled, for easy navigation (Cntl+Alt+L). From the solution explorer, right click on your project, and Add > New Item.
Choose ADO .NET Entity Data Model. Since we first have to generate our DB entity diagram within the context of the application we are making. Visual Studio lets us do this all using point and click.

In the choices for Model Contents, choose EF Designer from Database. Which would tell Visual Studio to intuitively design the entity model based on our DB table structure. Click Next.
At this point you are asked the details of the SQL server, to which it need to make the data connection. Click “New” button, to open the dialogue to initiate a new connection request. But now, you need to know the Server name your Azure DB. Where do you find that?
Well, log-in to the Azure Manage platform, go to the detail page of your DB, and there you would be able to find your Server name. Copy that, for use here. 
Once you have the server name, paste the values and enter the SQL authentication credentials that you specified when creating this DB. After a few minutes of wait, the available databases in the SQL server would be displayed. If you are getting an error pop up, it would be most likely because your current IP is not in the list of trusted IPs at Azure. Add your current IP to your DB’s trusted list. The database names might take a while to load, be patient. As long as you did not get an error, you are good. In the next step, choose “Yes, Include sensitive data… ” and further choose Entity model. That would give you a screen to choose what database elements need to be brought in context to this app.
The next broad task we are going to perform is to add a data service to this application. WCF Data Services enables you to create services that use the Open Data Protocol (OData) to expose and consume data over the Web or intranet. 
As you did above, in Step 3, right click on the Project and Add > New Item. In the selection pop up that is thrown, choose the WCF Data Services template from the Web category. Also be sure to give a proper name for this data service, since what you give here would appear as the last part for your OData URL.
Once you click add, Visual Studio would open up a template based DataServices class, that has neat instructions as to what to do. Notice a bunch of *TODO tags within the template. It narrates what exactly need to be filled in.
Fill in the [class name] in line 2. And remove the comment from the following line for code: “config.SetEntitySetAccessRule(“MyEntityset”, EntitySetRights.AllRead);”. And replace “MyEntityset” with “*”. This would grant read access to all data via this OData service.
That is it, you are done. Click to the browser button on the top pane, to check if everything is alright. If yes, you should be getting an XML output with a local version of your OData service.
Suffix the url with “$metadata” to get the entire meta data structure of your data base.

So now we have an OData service running from our local machine. But that might not be enough for other applications to consume. So, lets get this OData URI cloud-ized. How? Azure again.

Sign in to your Azure and via the New button, reach New > Web App > Quick create. Enter a neat looking URL, as this would constitute the first bit of your OData service URL.
Once the Web App is created, you would be taken to the web app dashboard; where you would find the option to “Download the Publisher Profile”. Publisher profile is a collection settings, that lets a third part app authenticate and publish applications to this hosted web application. Download and save the publisher profile to your computer.
Go back to Visual Studio, and right click on the Project, invoke the menu and choose “Publish”. If you don’t see the publish button enabled, it could be because you are in debug mode. There would be a “stop” button on header bar to get you out of the developer version. Post which you would be able to see the publish button.
After the web publishing is done by importing the publisher provide file that you saved a while ago. You would notice that most of the parameters regarding the web application gets filled automatically. And this is why, we choose to use the publisher profile import method. Now, click Publish.
It might take a while for the entire web application to get published onto Azure. Once done you would see a success page. Since there is no landing page or front end defined for our web application, it would be the generic Azure page.
Extend the URL by adding <yourODataServiceName.svc>, and you should be able to see the XML.

That’s it! You have just created a personalized custom OData service URL. 

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