Code-First Approach
An alternative to introspecting the model from the provider is to handwrite your model classes. This is the code-first approach to Entity Framework, which gives you greater control over the exact data model you use in your application.
Install Entity Framework
Install Entity Framework or add references to the required assemblies for your chosen version of Entity Framework. See Using EF 6 for using Entity Framework 6. See Installed Assemblies for more information about all assemblies shipped with the provider.
Register the Provider
Add the connection string to App.Config or Web.config. The connectionStrings node is often located directly below the configSection node in the root configuration node.
<configuration> ... <connectionStrings> <add name="DB2Context" connectionString="Server=10.0.1.2;Port=50000;User=admin;Password=admin;Database=test" providerName="System.Data.CData.DB2" /> </connectionStrings> ... </configuration>
Create the Context Class
Start by creating the DB2Context class. This is the base object that extends DbContext and exposes the DbSet properties that represent the tables in the data source. Next, override some of the default functionality of the DbContext class by overriding the OnModelCreating method. You can find a description of these properties in the code below:
C#
using System.Data.Entity;
using System.Data.Entity.Infrastructure;
using System.Data.Entity.ModelConfiguration.Conventions;
class DB2Context : DbContext {
public DB2Context() { }
public DbSet<Books> Books { set; get; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
// To remove the requests to the Migration History table
Database.SetInitializer<DB2Context>(null);
// To remove the plural names
modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
//For versions of EF before 6.0, uncomment the following line to remove calls to EdmTable, a metadata table
//modelBuilder.Conventions.Remove<IncludeMetadataConvention>();
//To remove the default schema "dbo"
modelBuilder.HasDefaultSchema("");
}
}
VB.NET
Imports System.Data.Entity
Imports System.Data.Entity.Infrastructure
Imports System.Data.Entity.ModelConfiguration.Conventions
Class DB2Context
Inherits DbContext
Public Sub New()
End Sub
public property Books As DbSet(Of Books)
Protected Overrides Sub OnModelCreating(modelBuilder As DbModelBuilder)
' To remove the requests to the Migration History table
Database.SetInitializer(of DB2Context)(Nothing)
' To remove the plural names
modelBuilder.Conventions.Remove(Of PluralizingTableNameConvention)
' For versions of EF before 6.0, uncomment the following line to remove calls to EdmTable, a metadata table
' modelBuilder.Conventions.Remove(Of IncludeMetadataConvention)()
' To remove the default schema "dbo"
modelBuilder.HasDefaultSchema("")
End Sub
End Class
Create the Table Models
Finally, define a class for each table that was defined in the DbSet properties of the context class. The table classes should have a list of properties that correspond to each field of that table. A corresponding map class must be defined to configure attributes for each property in the table class.
C#
using System.Data.Entity.ModelConfiguration;
using System.ComponentModel.DataAnnotations.Schema; //EF 6 and later
//using System.ComponentModel.DataAnnotations //For versions of EF before 6
[System.ComponentModel.DataAnnotations.Schema.Table("\"Sample\".\"DB2INST1\".Books")]
public class Books {
[System.ComponentModel.DataAnnotations.Key]
public System.String Id { get; set; }
public System.String Author { get; set; }
}
VB.NET
Imports System.Data.Entity.ModelConfiguration
Imports System.ComponentModel.DataAnnotations.Schema 'EF 6 and later
'Imports System.ComponentModel.DataAnnotations 'For versions of EF before 6
<System.ComponentModel.DataAnnotations.Schema.Table("\"Sample\".\"DB2INST1\".Books")>
public class Books
<System.ComponentModel.DataAnnotations.Key>
public property Id As System.String
public property Author As System.String
End Class
Perform LINQ Commands in Your Code
You are now ready to start using LINQ in your code. Be sure to declare (c#)"using System.Linq"/(VB.Net)"Imports System.Linq" in your file.
C#
DB2Context ents = new DB2Context();
var BooksQuery = from Books in ents.Books
orderby Books.Author
select Books;
VB.Net
Dim ents As DB2Context = New DB2Context()
Dim BooksQuery = From Books In ents.Books
Order By Books.Author
Select Books