How to Access Xero 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 Xero data through the CData ADO.NET Provider, providing you with more flexibility and control.

Getting Started

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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 Xero Entity Framework 6 assembly and the connection string.

   To connect, set the Schema connection property in addition to any authentication values. Xero offers authentication for private applications, public applications, and partner applications. Set the XeroAppAuthentication property to PUBLIC, PRIVATE, or PARTNER, depending on the type of application configured. To connect from a private application, you will additionally need to set the OAuthAccessToken, OAuthClientId, OAuthClientSecret, CertificateStoreType, CertificateStore, and CertificateStorePassword.

   To connect from a public or partner application, you can use the embedded OAuthClientId, OAuthClientSecret, and CallbackURL, or you can register an app to obtain your own OAuth values.

   See the "Getting Started" chapter of the help documentation for a guide to authenticating to Xero.

   
   <configuration>
      ... 
     <connectionStrings>
       <add name="XeroContext" connectionString="Offline=False;InitiateOAuth=GETANDREFRESH" providerName="System.Data.CData.Xero" />
     </connectionStrings>
     <entityFramework>
       <providers>
          ... 
         <provider invariantName="System.Data.CData.Xero" type="System.Data.CData.Xero.XeroProviderServices, System.Data.CData.Xero.Entities.EF6" />
       </providers>
     <entityFramework>
   </configuration>
   </code> 
   

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

7. Create another .cs file and name it after the Xero entity you are retrieving, for example, Items. 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("Items")]
   public class Items {
     [System.ComponentModel.DataAnnotations.Key] 
     public System.String Name { get; set; }
     public System.String QuantityOnHand { get; set; }
   }
       
   

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

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

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

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