Access Elasticsearch Data with Entity Framework 6

Entity Framework is an object-relational mapping framework that can be used to work with data as objects. While you can run the ADO.NET Entity Data Model wizard in Visual Studio to handle generating the Entity Model, this approach, the model-first approach, can put you at a disadvantage if there are changes in your data source or if you want more control over how the entities operate. In this article you will complete the code-first approach to accessing Elasticsearch data using the CData ADO.NET Provider.

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 Elasticsearch Entity Framework 6 assembly and the connection string.

   Set the Server and Port connection properties to connect. To authenticate, set the User and Password properties, PKI (public key infrastructure) properties, or both. To use PKI, set the SSLClientCert, SSLClientCertType, SSLClientCertSubject, and SSLClientCertPassword properties.

   The data provider uses X-Pack Security for TLS/SSL and authentication. To connect over TLS/SSL, prefix the Server value with 'https://'. Note: TLS/SSL and client authentication must be enabled on X-Pack to use PKI.

   Once the data provider is connected, X-Pack will then perform user authentication and grant role permissions based on the realms you have configured.

   <configuration> ... <connectionStrings> <add name="ElasticsearchContext" connectionString="Offline=False;Server=127.0.0.1;Port=9200;User=admin;Password=123456;" providerName="System.Data.CData.Elasticsearch" /> </connectionStrings> <entityFramework> <providers> ... <provider invariantName="System.Data.CData.Elasticsearch" type="System.Data.CData.Elasticsearch.ElasticsearchProviderServices, System.Data.CData.Elasticsearch.Entities.EF6" /> </providers> <entityFramework> </configuration> </code>
4. Add a reference to System.Data.CData.Elasticsearch.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 ElasticsearchContext. 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 ElasticsearchContext : DbContext { public ElasticsearchContext() { } protected override void OnModelCreating(DbModelBuilder modelBuilder) { // To remove the requests to the Migration History table Database.SetInitializer<ElasticsearchContext>(null); // To remove the plural names modelBuilder.Conventions.Remove<PluralizingTableNameConvention>(); } }
7. Create another .cs file and name it after the Elasticsearch entity you are retrieving, for example, Orders. 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("Orders")] public class Orders { [System.ComponentModel.DataAnnotations.Key] public System.String OrderName { get; set; } public System.String Freight { get; set; } }
8. Now that you have created an entity, add the entity to your context class: public DbSet<Orders> Orders { set; get; }
9. With the context and entity finished, you are now ready to query the data in a separate class. For example: ElasticsearchContext context = new ElasticsearchContext(); context.Configuration.UseDatabaseNullSemantics = true; var query = from line in context.Orders select line;