Internal Identity

This article is relevant to entity models that utilize the deprecated Visual Studio integration of Telerik Data Access. The current documentation of the Data Access framework is available here.

Telerik Data Access always needs to associate its persistent types with a primary key. If such is not supplied, Telerik Data Access uses internal mechanism for creating IDs. The internal identity (or High-Low) mechanism relies that a certain table (voa_keygen) is presented in your database. The internal identity field has an integer type and is calculated by the Telerik Data Access High-Low key generator. The voa_keygen table will be used for storage of the internal identities. Generally, the voa_keygen table will be used to connect the identity column of the table with the column value.

To configure internal identity with Fluent Mapping, you need to specify that the property that is part of the identity key uses the HighLow key generator. The following example demonstrates how to configure internal identity for the Person class.

personConfiguration.HasProperty( p => p.Id ).IsIdentity(KeyGenerator.HighLow);

personConfiguration.HasProperty(Function(p) p.Id).IsIdentity(KeyGenerator.HighLow)

In the previous example, it is supposed that the Person class has an integer property named Id that will be used as an internal identity.

However, if there isn't a specific property/column that could be used as an identity, Telerik Data Access will automatically create one:

personConfiguration.HasIdentity(KeyGenerator.HighLow);

personConfiguration.HasIdentity(KeyGenerator.HighLow)

When you update your database schema to the latest model state, Telerik Data Access will automatically create a new column ("TableName_Id"), which will be used as an internal primary key. The new column is of type SQL INTEGER.

Finally, you can explicitly specify the name for the internal identity column by using the ToColumn method:

personConfiguration.HasIdentity(KeyGenerator.HighLow).ToColumn("InternalIdentityColumn");

personConfiguration.HasIdentity(KeyGenerator.HighLow).ToColumn("InternalIdentityColumn")

For more information about the Telerik Data Access internal identity mechanism, see Working with HighLow Keygen API.

Person Class

public class Person
{
   public int Id {get;set;}
   public string FirstName {get;set;}
   public string LastName {get;set;}
   public string Address {get;set;}
}

Public Class Person
    Private _id As Integer
    Public Property Id() As Integer
        Get
            Return _id
        End Get
        Set(ByVal value As Integer)
            _id = value
        End Set
    End Property

    Private _firstName As String
    Public Property FirstName() As String
        Get
            Return _firstName
        End Get
        Set(ByVal value As String)
            _firstName = value
        End Set
    End Property

    Private _lastName As String
    Public Property LastName() As String
        Get
            Return _lastName
        End Get
        Set(ByVal value As String)
            _lastName = value
        End Set
    End Property

    Private _address As String
    Public Property Address() As String
        Get
            Return _address
        End Get
        Set(ByVal value As String)
            _address = value
        End Set
    End Property
End Class

Sample FluentMetadataSource Implementation - Internal Identity

public class FluentModelMetadataSource : FluentMetadataSource
{
   protected override IList<MappingConfiguration> PrepareMapping()
   {
       List<MappingConfiguration> configurations = new List<MappingConfiguration>();

       MappingConfiguration<Person> personConfiguration = new MappingConfiguration<Person>();
       personConfiguration.MapType( p => new
       {
           Id = p.Id,
           FirstName = p.FirstName,
           LastName = p.LastName,
           HomeAddress = p.Address
       } ).ToTable( "People" );

       personConfiguration.HasProperty( p => p.Id ).IsIdentity(KeyGenerator.HighLow);

       configurations.Add( personConfiguration );
       return configurations;
   }
}

Public Class FluentModelMetadataSource
    Inherits FluentMetadataSource
    Protected Overrides Function PrepareMapping() As _
        System.Collections.Generic.IList(Of Telerik.OpenAccess.Metadata.Fluent.MappingConfiguration)
        Dim configurations As List(Of MappingConfiguration) = New List(Of MappingConfiguration)()
        Dim personConfiguration As New MappingConfiguration(Of Person)()

        personConfiguration.MapType(Function(p) New With {Key .Id = p.Id,
                                          Key .FirstName = p.FirstName,
                                          Key .LastName = p.LastName,
                                          Key .HomeAddress = p.Address}).ToTable("People")

        personConfiguration.HasProperty(Function(p) p.Id).IsIdentity(KeyGenerator.HighLow)

        personConfiguration.FieldNamingRules.AddPrefix = "_"
        configurations.Add(personConfiguration)
        Return configurations
    End Function
End Class