X509Extension Class

 
System_CAPS_noteNote

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Represents an X509 extension.

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


Public Class X509Extension
	Inherits AsnEncodedData

NameDescription
System_CAPS_protmethodX509Extension()

Initializes a new instance of the X509Extension class.

System_CAPS_pubmethodX509Extension(AsnEncodedData, Boolean)

Initializes a new instance of the X509Extension class.

System_CAPS_pubmethodX509Extension(Oid, Byte(), Boolean)

Initializes a new instance of the X509Extension class.

System_CAPS_pubmethodX509Extension(String, Byte(), Boolean)

Initializes a new instance of the X509Extension class.

NameDescription
System_CAPS_pubpropertyCritical

Gets a Boolean value indicating whether the extension is critical.

System_CAPS_pubpropertyOid

Gets or sets the Oid value for an AsnEncodedData object.(Inherited from AsnEncodedData.)

System_CAPS_pubpropertyRawData

Gets or sets the Abstract Syntax Notation One (ASN.1)-encoded data represented in a byte array.(Inherited from AsnEncodedData.)

NameDescription
System_CAPS_pubmethodCopyFrom(AsnEncodedData)

Copies the extension properties of the specified AsnEncodedData object.(Overrides AsnEncodedData.CopyFrom(AsnEncodedData).)

System_CAPS_pubmethodEquals(Object)

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_protmethodFinalize()

Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)

System_CAPS_pubmethodFormat(Boolean)

Returns a formatted version of the Abstract Syntax Notation One (ASN.1)-encoded data as a string.(Inherited from AsnEncodedData.)

System_CAPS_pubmethodGetHashCode()

Serves as the default hash function. (Inherited from Object.)

System_CAPS_pubmethodGetType()

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_protmethodMemberwiseClone()

Creates a shallow copy of the current Object.(Inherited from Object.)

System_CAPS_pubmethodToString()

Returns a string that represents the current object.(Inherited from Object.)

X509 extensions are dynamic, extended properties that can be added to an X509 certificate and changed. The X509Extension class can be used to create extensions that are associated with a certificate but are not part of a certificate as issued by a certification authority (CA).

In its most basic form, an X509 extension has an object identifier (OID), a Boolean value describing whether the extension is considered critical or not, and ASN-encoded data. Custom extensions can be registered in a CryptoConfig file.

The.NET Framework includes implementations of several common X509 extensions:

The following code example demonstrates using the X509Extension class.

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
Available since 2.0

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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