Provide OData Services of Google Spanner Data from a WCF Application

The CData ADO.NET Provider for Google Spanner enables you to use the Windows Communication Foundation (WCF) framework to rapidly develop service-oriented applications that provide Google Spanner data to OData consumers. This article shows how to create an entity data model to provide the underlying connectivity to the Google Spanner data, as well as how to create a WCF Data Service to expose the OData service. You can then consume the feed with any OData client, for example, Power Pivot or an application that uses the CData ADO.NET Provider for OData.

Create the OData Service

Follow the steps below to create a WCF service application that will provide connectivity to Google Spanner data via OData.

1. Open Visual Studio and create a new project. Select the WCF Service Application template.
2. Delete the autogenerated IService.cs and Service1.svc.
3. Click Project -> Add New Item -> ADO.NET Entity Data Model.
4. In the Entity Data Model wizard that is displayed, select the 'EF Designer from Database' option.
5. In the resulting Choose Your Connection dialog, click New Connection.

6. In the Connection properties dialog, select the CData Google Spanner Data Source and enter the necessary credentials. A typical connection string is below:

   ProjectId='project1';InstanceId='instance1';Database='db1';

   Google Spanner uses the OAuth authentication standard. To authenticate using OAuth, you can use the embedded credentials or register an app with Google.

   See the Getting Started guide in the CData driver documentation for more information.

   See the help documentation for guides to connecting in Visual Studio.

   
7. Select Google Spanner tables and views that you want OData clients to access.
8. Click Project -> Add New Item -> WCF Data Service.

9. Specify the data source class and configure access to the new WCF Data Service. In the example below, the Access Rule for the entities is set to All. This means that any user will be able to read and modify data.

   using System; using System.Collections.Generic; using System.Data.Services; using System.Data.Services.Common; using System.Linq; using System.ServiceModel.Web; using System.Web; namespace GoogleSpannerService{ public class GoogleSpannerDataService : DataService { public static void InitializeService(DataServiceConfiguration config) { config.SetEntitySetAccessRule("*", EntitySetRights.All); config.DataServiceBehavior.MaxProtocolVersion = DataServiceProtocolVersion.V3; } } }
10. Run the project. Applications that support OData can now access the Salesforce data and reflect any changes. You can access the feed in your browser. The feed will resemble the following:

Consume the OData Service from Power Pivot

You can now use the service from any OData client; for example, Excel Power Pivot.

1. Open Excel and click on the Power Pivot Window button.
2. A new pop-up will appear. Select the option From Data Feeds.
3. In the resulting Table Import Wizard, enter the OData URL. For example, http://localhost:12449/GoogleSpannerDataService.svc/.
4. After connecting to the OData service, click the Next button at the bottom of the window.
5. A table listing of the available tables will appear in the next window of the wizard. Select which tables you want to import and click Finish.
6. Click Close to import the data in Power Pivot.