X509KeyUsageExtension Class
.NET Framework 3.0
Defines the usage of a key contained within an X.509 certificate. This class cannot be inherited.
Namespace: System.Security.Cryptography.X509Certificates
Assembly: System (in system.dll)
Assembly: System (in system.dll)
The X509KeyUsageExtension class uses the flags in the X509KeyUsageFlags enumeration to define or determine key usage.
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 X509KeyUsageExtension 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
System.Object
System.Security.Cryptography.AsnEncodedData
System.Security.Cryptography.X509Certificates.X509Extension
System.Security.Cryptography.X509Certificates.X509KeyUsageExtension
System.Security.Cryptography.AsnEncodedData
System.Security.Cryptography.X509Certificates.X509Extension
System.Security.Cryptography.X509Certificates.X509KeyUsageExtension
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.Community Additions
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