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MetadataTypeAttribute Class

Updated: July 2008

Specifies the metadata class to associate with a data model class.

Namespace:  System.ComponentModel.DataAnnotations
Assembly:  System.ComponentModel.DataAnnotations (in System.ComponentModel.DataAnnotations.dll)

[AttributeUsageAttribute(AttributeTargets.Class, AllowMultiple = false, Inherited = false)]
public sealed class MetadataTypeAttribute : Attribute

The MetadataTypeAttribute 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 MetadataTypeAttribute 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 MetadataTypeAttribute 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 MetadataTypeAttribute 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.

using System;
using System.Web.DynamicData;
using System.ComponentModel.DataAnnotations;

[MetadataType(typeof(CustomerMetaData))]
public partial class Customer
{


}


public class CustomerMetaData
{
    // Apply RequiredAttribute
    [Required(ErrorMessage = "Title is required.")]
    public object Title;


}

System.Object
  System.Attribute
    System.ComponentModel.DataAnnotations.MetadataTypeAttribute

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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.

.NET Framework

Supported in: 3.5 SP1

Date

History

Reason

July 2008

Added topic for new class.

SP1 feature change.

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