Provide OData Services of Gmail Data from a WCF Application

The CData ADO.NET Provider for Gmail enables you to rapidly develop service-oriented applications using the Windows Communication Foundation (WCF) framework, providing Gmail data data to OData consumers. This article guides you through creating an entity data model for connectivity and a WCF Data Service to expose OData services. You can then consume the feed with various OData clients, such as Power Pivot or applications using 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 Gmail 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. Install Entity Framework 6:

   Use the Package Manager Console in Visual Studio to install the latest version of Entity Framework. Run the following command to download and install Entity Framework automatically:

   Install-Package EntityFramework

4. Register the Entity Framework provider:
   1. Add the following provider entry in the "providers" section of your App.config or Web.config file. This section should already exist if the Entity Framework installation was successful.

      <configuration>
      ...
      <entityFramework>
       <providers>
       ...
       <provider invariantName="System.Data.CData.Gmail" type="System.Data.CData.Gmail.GmailProviderServices, System.Data.CData.Gmail.Entities.EF6" />
       </providers>
      </entityFramework>
      </configuration>

   2. Add a reference to System.Data.CData.Gmail.Entities.dll, located in lib/4.0 in the installation directory.
   3. Build the project to complete the setup for using EF6.
5. Click Project -> Add New Item -> ADO.NET Entity Data Model.
6. In the Entity Data Model wizard that is displayed, select the 'EF Designer from Database' option.
7. In the resulting Choose Your Connection dialog, click New Connection.

8. In the Connection properties dialog, select the CData Gmail Data Source and enter the necessary credentials.

   A typical connection string is below:

   User=username;Password=password;

   There are two ways to authenticate to Gmail. Before selecting one, first ensure that you have enabled IMAP access in your Gmail account settings. See the "Connecting to Gmail" section under "Getting Started" in the installed documentation for a guide.

   The User and Password properties, under the Authentication section, can be set to valid Gmail user credentials.

   Alternatively, instead of providing the Password, you can use the OAuth authentication standard. To access Google APIs on behalf on individual users, you can use the embedded credentials or you can register your own OAuth app.

   OAuth also enables you to use a service account to connect on behalf of users in a Google Apps domain. To authenticate with a service account, register an application to obtain the OAuth JWT values.

   In addition to the OAuth values, provide the User. See the "Getting Started" chapter in the help documentation for a guide to using OAuth.

   👁 Required connection properties, specified in the Add Connection dialog. (Salesforce is shown.)
   
9. Select Gmail tables and views that you want OData clients to access. 👁 Available tables in the Entity Data Model Wizard. (Salesforce is shown.)
   
10. Click Project -> Add New Item -> WCF Data Service.

11. 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 GmailService{
     public class GmailDataService : DataService<GmailEntities> {
     public static void InitializeService(DataServiceConfiguration config) {
     config.SetEntitySetAccessRule("*", EntitySetRights.All);
     config.DataServiceBehavior.MaxProtocolVersion = DataServiceProtocolVersion.V3;
     }
     }
    }
    	

12. 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: 👁 The raw OData feed. (Salesforce is shown.)
    

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/GmailDataService.svc/. 👁 The OData URL for Gmail.
   
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. 👁 Available tables in the Table Import Wizard. (Salesforce is shown.)
   
6. Click Close to import the data in Power Pivot. 👁 The table loaded in Power Pivot. (Salesforce is shown.)