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

   The DataSource property must be set to a valid local folder name.

   Also, specify the IncludeFiles property to work with text files having extensions that differ from .csv, .tab, or .txt. Specify multiple file extensions in a comma-separated list. You can also set Extended Properties compatible with the Microsoft Jet OLE DB 4.0 driver. Alternatively, you can provide the format of text files in a Schema.ini file.

   Set UseRowNumbers to true if you are deleting or updating in CSV. This will create a new column with the name RowNumber which will be used as key for that table.

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