Updated: July 2008
Specifies the metadata class to associate with a data model class.
Assembly: System.ComponentModel.DataAnnotations (in System.ComponentModel.DataAnnotations.dll)
The attribute enables you to associate a class with a data-model partial class. In this associated class you provide additional metadata information that is not in the data model.
For example, in the associated class you can apply the RequiredAttribute attribute to a data field. This enforces that a value is provided for the field even if this constraint is not required by the database schema.
You use the attribute as follows:
In your application, create a file in which you create the data-model partial class that you want to modify.
Create the associated metadata class.
Apply the attribute to the partial entity class, specifying the associated class.
When you apply this attribute, you must adhere to the following usage constraints:
The attribute can only be applied to a class.
The attribute cannot be inherited by derived classes.
The attribute can be applied only one time.
The following example shows how to use the to associate a metadata class with an entity partial class. The example applies the RequiredAttribute attribute to a data field to show how to provide additional information in the associated metadata class.
Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.