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

   Connecting to Local SASXpt Files

   You can connect to local SASXpt file by setting the URI to a folder containing SASXpt files.

   Connecting to S3 data source

   You can connect to Amazon S3 source to read SASXpt files. Set the following properties to connect:

   • URI: Set this to the folder within your bucket that you would like to connect to.
   • AWSAccessKey: Set this to your AWS account access key.
   • AWSSecretKey: Set this to your AWS account secret key.
   • TemporaryLocalFolder: Set this to the path, or URI, to the folder that is used to temporarily download SASXpt file(s).

   Connecting to Azure Data Lake Storage Gen2

   You can connect to ADLS Gen2 to read SASXpt files. Set the following properties to connect:

   • URI: Set this to the name of the file system and the name of the folder which contacts your SASXpt files.
   • AzureAccount: Set this to the name of the Azure Data Lake storage account.
   • AzureAccessKey: Set this to our Azure DataLakeStore Gen 2 storage account access key.
   • TemporaryLocalFolder: Set this to the path, or URI, to the folder that is used to temporarily download SASXpt file(s).

   <configuration>
    ... 
    <connectionStrings>
    <add name="SASXptContext" connectionString="Offline=False;URI=C:/folder;" providerName="System.Data.CData.SASXpt" />
    </connectionStrings>
    <entityFramework>
    <providers>
    ... 
    <provider invariantName="System.Data.CData.SASXpt" type="System.Data.CData.SASXpt.SASXptProviderServices, System.Data.CData.SASXpt.Entities.EF6" />
    </providers>
    <entityFramework>
   </configuration>
   </code> 
   

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

7. Create another .cs file and name it after the SAS xpt entity you are retrieving, for example, SampleTable_1. 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("SampleTable_1")]
   public class SampleTable_1 {
    [System.ComponentModel.DataAnnotations.Key] 
    public System.String Id { get; set; }
    public System.String Column1 { get; set; }
   }
    
   

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

   public DbSet<SampleTable_1> SampleTable_1 { set; get; }
   

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

   SASXptContext context = new SASXptContext();
   context.Configuration.UseDatabaseNullSemantics = true;
   var query = from line in context.SampleTable_1 select line;