MetadataTypeAttribute Class (System.ComponentModel.DataAnnotations)

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MetadataTypeAttribute Class

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

Inheritance Hierarchy
System.Object
  System.Attribute
    System.ComponentModel.DataAnnotations.MetadataTypeAttribute

Namespace:  System.ComponentModel.DataAnnotations
Assembly:  System.ComponentModel.DataAnnotations (in System.ComponentModel.DataAnnotations.dll)
Syntax
Visual Basic
<AttributeUsageAttribute(AttributeTargets.Class, AllowMultiple := False)> _
Public NotInheritable Class MetadataTypeAttribute _
	Inherits Attribute
C#
[AttributeUsageAttribute(AttributeTargets.Class, AllowMultiple = false)]
public sealed class MetadataTypeAttribute : Attribute
Visual C++
[AttributeUsageAttribute(AttributeTargets::Class, AllowMultiple = false)]
public ref class MetadataTypeAttribute sealed : public Attribute
F#
[<Sealed>]
[<AttributeUsageAttribute(AttributeTargets.Class, AllowMultiple = false)>]
type MetadataTypeAttribute =  
    class
        inherit Attribute
    end

The MetadataTypeAttribute type exposes the following members.

Constructors
  Name Description
Public method MetadataTypeAttribute Initializes a new instance of the MetadataTypeAttribute class.
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Properties
  Name Description
Public property MetadataClassType Gets the metadata class that is associated with a data-model partial class.
Public property TypeId When implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute.)
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Methods
  Name Description
Public method Equals Infrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.)
Protected method Finalize Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public method GetHashCode Returns the hash code for this instance. (Inherited from Attribute.)
Public method GetType Gets the Type of the current instance. (Inherited from Object.)
Public method IsDefaultAttribute When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute.)
Public method Match When overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
Protected method MemberwiseClone Creates a shallow copy of the current Object. (Inherited from Object.)
Public method ToString Returns a string that represents the current object. (Inherited from Object.)
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Explicit Interface Implementations
  Name Description
Explicit interface implemetation Private method _Attribute.GetIDsOfNames Maps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute.)
Explicit interface implemetation Private method _Attribute.GetTypeInfo Retrieves the type information for an object, which can be used to get the type information for an interface. (Inherited from Attribute.)
Explicit interface implemetation Private method _Attribute.GetTypeInfoCount Retrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute.)
Explicit interface implemetation Private method _Attribute.Invoke Provides access to properties and methods exposed by an object. (Inherited from Attribute.)
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Remarks

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.

Examples

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.

Visual Basic

Imports System
Imports System.Web.DynamicData
Imports System.ComponentModel.DataAnnotations

<MetadataType(GetType(CustomerMetadata))> _
Partial Public Class Customer

End Class

Public Class CustomerMetadata

    ' Apply RequitedAttribute.
    <Required(ErrorMessage:="Title is required.")> _
    Public Title As Object


End Class
C#

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;


}
Version Information

.NET Framework

Supported in: 4, 3.5 SP1

.NET Framework Client Profile

Supported in: 4
Platforms

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
Thread Safety
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
See Also

Reference

System.ComponentModel.DataAnnotations Namespace