How to Access ConstantContact 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 ConstantContact 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 ConstantContact Entity Framework 6 assembly and the connection string.

   Start by setting the Profile connection property to the location of the ConstantContact Profile on disk (e.g. C:\profiles\ConstantContact.apip). Next, set the ProfileSettings connection property to the connection string for Profile (see below).

   ConstantContact API Profile Settings

   ConstantContact uses OAuth-based authentication.

   First, you will need to register an OAuth application with ConstantContact. You can do so from the ConstantContact API Guide (https://v3.developer.constantcontact.com/api_guide/index.html), under "MyApplications" > "New Application". Your Oauth application will be assigned a client id (API Key) and you can generate a client secret (Secret).

   After setting the following connection properties, you are ready to connect:

   • AuthScheme: Set this to OAuth.
   • InitiateOAuth: Set this to GETANDREFRESH. You can use InitiateOAuth to manage the process to obtain the OAuthAccessToken.
   • OAuthClientId: Set this to the client_id that is specified in you app settings.
   • OAuthClientSecret: Set this to the client_secret that is specified in you app settings.
   • CallbackURL: Set this to the Redirect URI you specified in your app settings.
   <configuration> ... <connectionStrings> <add name="APIContext" connectionString="Offline=False;Profile=C:\profiles\ConstantContact.apip;Authscheme=OAuth;OAuthClientId=your_client_id;OAuthClientSecret=your_client_secret;CallbackUrl=your_callback_url;" providerName="System.Data.CData.API" /> </connectionStrings> <entityFramework> <providers> ... <provider invariantName="System.Data.CData.API" type="System.Data.CData.API.APIProviderServices, System.Data.CData.API.Entities.EF6" /> </providers> <entityFramework> </configuration> </code>
4. Add a reference to System.Data.CData.API.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 APIContext. 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 APIContext : DbContext { public APIContext() { } protected override void OnModelCreating(DbModelBuilder modelBuilder) { // To remove the requests to the Migration History table Database.SetInitializer<APIContext>(null); // To remove the plural names modelBuilder.Conventions.Remove<PluralizingTableNameConvention>(); } }
7. Create another .cs file and name it after the ConstantContact entity you are retrieving, for example, Contacts. 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("Contacts")] public class Contacts { [System.ComponentModel.DataAnnotations.Key] public System.String Id { get; set; } public System.String EmailAddress { get; set; } }
8. Now that you have created an entity, add the entity to your context class: public DbSet<Contacts> Contacts { set; get; }
9. With the context and entity finished, you are now ready to query the data in a separate class. For example: APIContext context = new APIContext(); context.Configuration.UseDatabaseNullSemantics = true; var query = from line in context.Contacts select line;