X509EnhancedKeyUsageExtension Class

Defines the collection of object identifiers (OIDs) that indicates the applications that use the key. This class cannot be inherited.

Namespace: System.Security.Cryptography.X509Certificates
Assembly: System (in system.dll)

Public NotInheritable Class X509EnhancedKeyUsageExtension
	Inherits X509Extension
Dim instance As X509EnhancedKeyUsageExtension

public final class X509EnhancedKeyUsageExtension extends X509Extension
public final class X509EnhancedKeyUsageExtension extends X509Extension
Not applicable.

An enhanced key usage (EKU) extension is a collection of object identifiers (OIDs) that indicate the applications that use the key.

The following code example demonstrates how to open a user’s personal certificate store and display information about each certificate in the store. This example uses the X509EnhancedKeyUsageExtension class to display the information.

Imports System
Imports System.Security.Cryptography
Imports System.Security.Cryptography.X509Certificates

Module CertSelect

    Sub Main()
            Dim store As New X509Store("MY", StoreLocation.CurrentUser)
            store.Open(OpenFlags.ReadOnly Or OpenFlags.OpenExistingOnly)

            Dim collection As X509Certificate2Collection = CType(store.Certificates, X509Certificate2Collection)
            Dim i As Integer
            For i = 0 To collection.Count
                Dim extension As X509Extension
                For Each extension In collection(i).Extensions
                    Console.WriteLine(extension.Oid.FriendlyName + "(" + extension.Oid.Value + ")")

                    If extension.Oid.FriendlyName = "Key Usage" Then
                        Dim ext As X509KeyUsageExtension = CType(extension, X509KeyUsageExtension)
                    End If

                    If extension.Oid.FriendlyName = "Basic Constraints" Then
                        Dim ext As X509BasicConstraintsExtension = CType(extension, X509BasicConstraintsExtension)
                    End If

                    If extension.Oid.FriendlyName = "Subject Key Identifier" Then
                        Dim ext As X509SubjectKeyIdentifierExtension = CType(extension, X509SubjectKeyIdentifierExtension)
                    End If

                    If extension.Oid.FriendlyName = "Enhanced Key Usage" Then
                        Dim ext As X509EnhancedKeyUsageExtension = CType(extension, X509EnhancedKeyUsageExtension)
                        Dim oids As OidCollection = ext.EnhancedKeyUsages
                        Dim oid As Oid
                        For Each oid In oids
                            Console.WriteLine(oid.FriendlyName + "(" + oid.Value + ")")
                        Next oid
                    End If
                Next extension
            Next i
            Console.WriteLine("Information could not be written out for this certificate.")
        End Try

    End Sub
End Module


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 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0