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X509EnhancedKeyUsageExtension Class

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

System.Object
  System.Security.Cryptography.AsnEncodedData
    System.Security.Cryptography.X509Certificates.X509Extension
      System.Security.Cryptography.X509Certificates.X509EnhancedKeyUsageExtension

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

'Declaration
Public NotInheritable Class X509EnhancedKeyUsageExtension _
	Inherits X509Extension

The X509EnhancedKeyUsageExtension type exposes the following members.

  NameDescription
Public methodX509EnhancedKeyUsageExtensionInitializes a new instance of the X509EnhancedKeyUsageExtension class.
Public methodX509EnhancedKeyUsageExtension(AsnEncodedData, Boolean)Initializes a new instance of the X509EnhancedKeyUsageExtension class using an AsnEncodedData object and a value that identifies whether the extension is critical.
Public methodX509EnhancedKeyUsageExtension(OidCollection, Boolean)Initializes a new instance of the X509EnhancedKeyUsageExtension class using an OidCollection and a value that identifies whether the extension is critical.
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  NameDescription
Public propertyCriticalGets a Boolean value indicating whether the extension is critical. (Inherited from X509Extension.)
Public propertyEnhancedKeyUsagesGets the collection of object identifiers (OIDs) that indicate the applications that use the key.
Public propertyOidGets or sets the Oid value for an AsnEncodedData object. (Inherited from AsnEncodedData.)
Public propertyRawDataGets or sets the Abstract Syntax Notation One (ASN.1)-encoded data represented in a byte array. (Inherited from AsnEncodedData.)
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  NameDescription
Public methodCopyFromInitializes a new instance of the X509EnhancedKeyUsageExtension class using an AsnEncodedData object. (Overrides X509Extension.CopyFrom(AsnEncodedData).)
Public methodEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Public methodFormatReturns a formatted version of the Abstract Syntax Notation One (ASN.1)-encoded data as a string. (Inherited from AsnEncodedData.)
Public methodGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
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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()
        Try 
            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)
                        Console.WriteLine(ext.KeyUsages)
                    End If 

                    If extension.Oid.FriendlyName = "Basic Constraints" Then 
                        Dim ext As X509BasicConstraintsExtension = CType(extension, X509BasicConstraintsExtension)
                        Console.WriteLine(ext.CertificateAuthority)
                        Console.WriteLine(ext.HasPathLengthConstraint)
                        Console.WriteLine(ext.PathLengthConstraint)
                    End If 

                    If extension.Oid.FriendlyName = "Subject Key Identifier" Then 
                        Dim ext As X509SubjectKeyIdentifierExtension = CType(extension, X509SubjectKeyIdentifierExtension)
                        Console.WriteLine(ext.SubjectKeyIdentifier)
                    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
            store.Close()
        Catch
            Console.WriteLine("Information could not be written out for this certificate.")
        End Try 

    End Sub 
End Module

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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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