Статья
11/17/2011

KeyAttribute Class

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Specifies one or more entity properties to use as the unique identity for the entity.

Inheritance Hierarchy

System.Object
System.Attribute
System.ComponentModel.DataAnnotations.KeyAttribute

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

Syntax

'Declaration
<AttributeUsageAttribute(AttributeTargets.Property Or AttributeTargets.Field, AllowMultiple := False,  _
    Inherited := True)> _
Public NotInheritable Class KeyAttribute _
    Inherits Attribute

[AttributeUsageAttribute(AttributeTargets.Property|AttributeTargets.Field, AllowMultiple = false, 
    Inherited = true)]
public sealed class KeyAttribute : Attribute

The KeyAttribute type exposes the following members.

Constructors

	Name	Description
	KeyAttribute	Initializes a new instance of the KeyAttribute class.

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Methods

	Name	Description
	Equals	Infrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetHashCode	Returns the hash code for this instance. (Inherited from Attribute.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	Match	When overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	ToString	Returns a string that represents the current object. (Inherited from Object.)

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Remarks

You apply the KeyAttribute attribute to one or more properties to specify the values that uniquely identify the entity object.

Examples

The following example shows a KeyAttribute applied to a property named ProductID that uniquely identifies the individual data records represented by this class.

Public Class Product
  <Key()> _
  Public Property ProductID As Integer
    'Implement Get and Set logic
  End Property
End Class

public class Product
{
  [Key]
  public integer ProductID { get; set; }
}

Version Information

Silverlight

Supported in: 5, 4, 3

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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.

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