How to Access Google Data Catalog Data Using Entity Framework

Microsoft Entity Framework serves as an object-relational mapping framework for working with data represented as objects. Although Visual Studio offers the ADO.NET Entity Data Model wizard to automatically generate the Entity Model, this model-first approach may present challenges when your data source undergoes changes or when you require greater control over entity operations. In this article, we will delve into the code-first approach for accessing Google Data Catalog data through the CData ADO.NET Provider, providing you with more flexibility and control.

1. Open Visual Studio and create a new Windows Form Application. This article uses a C# project with .NET 4.5.
2. Run the command 'Install-Package EntityFramework' in the Package Manger Console in Visual Studio to install the latest release of Entity Framework.

3. Modify the App.config file in the project to add a reference to the Google Data Catalog Entity Framework 6 assembly and the connection string.

   Google Data Catalog uses the OAuth authentication standard. Authorize access to Google APIs on behalf on individual users or on behalf of users in a domain.

   Before connecting, specify the following to identify the organization and project you would like to connect to:

   • OrganizationId: The ID associated with the Google Cloud Platform organization resource you would like to connect to. Find this by navigating to the cloud console.

     Click the project selection drop-down, and select your organization from the list. Then, click More -> Settings. The organization ID is displayed on this page.

   • ProjectId: The ID associated with the Google Cloud Platform project resource you would like to connect to.

     Find this by navigating to the cloud console dashboard and selecting your project from the Select from drop-down. The project ID will be present in the Project info card.

   When you connect, the OAuth endpoint opens in your default browser. Log in and grant permissions to the application to completes the OAuth process. For more information, refer to the OAuth section in the Help documentation.

   <configuration> ... <connectionStrings> <add name="GoogleDataCatalogContext" connectionString="Offline=False;ProjectId=YourProjectId;InitiateOAuth=GETANDREFRESH" providerName="System.Data.CData.GoogleDataCatalog" /> </connectionStrings> <entityFramework> <providers> ... <provider invariantName="System.Data.CData.GoogleDataCatalog" type="System.Data.CData.GoogleDataCatalog.GoogleDataCatalogProviderServices, System.Data.CData.GoogleDataCatalog.Entities.EF6" /> </providers> <entityFramework> </configuration> </code>
4. Add a reference to System.Data.CData.GoogleDataCatalog.Entities.EF6.dll, located in the lib -> 4.0 subfolder in the installation directory.
5. Build the project at this point to ensure everything is working correctly. Once that's done, you can start coding using Entity Framework.
6. Add a new .cs file to the project and add a class to it. This will be your database context, and it will extend the DbContext class. In the example, this class is named GoogleDataCatalogContext. The following code example overrides the OnModelCreating method to make the following changes:
   • Remove PluralizingTableNameConvention from the ModelBuilder Conventions.
   • Remove requests to the MigrationHistory table.
   using System.Data.Entity; using System.Data.Entity.Infrastructure; using System.Data.Entity.ModelConfiguration.Conventions; class GoogleDataCatalogContext : DbContext { public GoogleDataCatalogContext() { } protected override void OnModelCreating(DbModelBuilder modelBuilder) { // To remove the requests to the Migration History table Database.SetInitializer<GoogleDataCatalogContext>(null); // To remove the plural names modelBuilder.Conventions.Remove<PluralizingTableNameConvention>(); } }
7. Create another .cs file and name it after the Google Data Catalog entity you are retrieving, for example, Schemas. In this file, define both the Entity and the Entity Configuration, which will resemble the example below: using System.Data.Entity.ModelConfiguration; using System.ComponentModel.DataAnnotations.Schema; [System.ComponentModel.DataAnnotations.Schema.Table("Schemas")] public class Schemas { [System.ComponentModel.DataAnnotations.Key] public System.String Type { get; set; } public System.String DatasetName { get; set; } }
8. Now that you have created an entity, add the entity to your context class: public DbSet<Schemas> Schemas { set; get; }
9. With the context and entity finished, you are now ready to query the data in a separate class. For example: GoogleDataCatalogContext context = new GoogleDataCatalogContext(); context.Configuration.UseDatabaseNullSemantics = true; var query = from line in context.Schemas select line;