How to Access SAP Netweaver Gateway 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 SAP Netweaver Gateway 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 SAP Netweaver Gateway Entity Framework 6 assembly and the connection string.

   SAP Gateway allows both basic and OAuth 2.0 authentication. You can use basic authentication to connect to your own account, or you can use OAuth to enable other users to retrieve data from your service with their accounts. In addition to authenticating, set the following connection properties to access SAP Gateway tables.

   • Url: Set this to the URL of your environment, or to the full URL of the service. For example, the full URL might appear as: https://sapes5.sapdevcenter.com/sap/opu/odata/IWBEP/GWSAMPLE_BASIC/. In this example, the environment URL would just be: https://sapes5.sapdevcenter.com.
   • Namespace: Set the appropriate Service Namespace. In the example above, IWBEP is the namespace. It is optional if the full URL to the service is specified.
   • Service: Set this to the service you want to retrieve data from. In the example above, the service is GWSAMPLE_BASIC. It is not required if the full URL is specified.

   Authenticate via Basic Authentication

   In basic authentication, you use your login credentials to connect. Set the following properties:

   • User: This is the username you use to log in to SAP Gateway.
   • Password: This is the password you use to log in to SAP Gateway.

   Authenticate via OAuth Authentication

   You can connect to SAP Gateway using the embedded OAuth connectivity (without setting any additional authentication connection properties). When you connect, the OAuth endpoint opens in your browser. Log in and grant permissions to complete the OAuth process. See the OAuth section in the online Help documentation for more information on other OAuth authentication flows.

   <configuration>
    ... 
    <connectionStrings>
    <add name="SAPGatewayContext" connectionString="Offline=False;User=user;Password=password;URL=https://sapes5.sapdevcenter.com/sap/opu/odata/IWBEP/GWSAMPLE_BASIC/;InitiateOAuth=GETANDREFRESH;" providerName="System.Data.CData.SAPGateway" />
    </connectionStrings>
    <entityFramework>
    <providers>
    ... 
    <provider invariantName="System.Data.CData.SAPGateway" type="System.Data.CData.SAPGateway.SAPGatewayProviderServices, System.Data.CData.SAPGateway.Entities.EF6" />
    </providers>
    <entityFramework>
   </configuration>
   </code> 
   

4. Add a reference to System.Data.CData.SAPGateway.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 SAPGatewayContext. 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 SAPGatewayContext : DbContext {
    public SAPGatewayContext() { }
   
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
    // To remove the requests to the Migration History table
    Database.SetInitializer<SAPGatewayContext>(null); 
    // To remove the plural names 
    modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
    } 
   }
   

7. Create another .cs file and name it after the SAP Netweaver Gateway entity you are retrieving, for example, SalesOrderLineItems. 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("SalesOrderLineItems")]
   public class SalesOrderLineItems {
    [System.ComponentModel.DataAnnotations.Key] 
    public System.String ProductID { get; set; }
    public System.String Quantity { get; set; }
   }
    
   

8. Now that you have created an entity, add the entity to your context class:

   public DbSet<SalesOrderLineItems> SalesOrderLineItems { set; get; }
   

9. With the context and entity finished, you are now ready to query the data in a separate class. For example:

   SAPGatewayContext context = new SAPGatewayContext();
   context.Configuration.UseDatabaseNullSemantics = true;
   var query = from line in context.SalesOrderLineItems select line;