X509Certificate2.Extensions Property

Definition

Namespace:

System.Security.Cryptography.X509Certificates

Assemblies:

netstandard.dll, System.Security.Cryptography.dll

Source:

X509Certificate2.cs

Gets a collection of X509Extension objects.

C#

public System.Security.Cryptography.X509Certificates.X509ExtensionCollection Extensions { get; }

Property Value

X509ExtensionCollection

An X509ExtensionCollection object.

Exceptions

CryptographicException

The certificate is unreadable.

Examples

The following code example opens the current user certificate store, selects only active certificates, then allows the user to select one or more certificates. The example then writes certificate information to the console.

C#

using System;
using System.Security.Cryptography;
using System.Security.Permissions;
using System.IO;
using System.Security.Cryptography.X509Certificates;

class CertSelect
{
    static void Main()
    {
        X509Store store = new X509Store("MY",StoreLocation.CurrentUser);
        store.Open(OpenFlags.ReadOnly | OpenFlags.OpenExistingOnly);

        X509Certificate2Collection collection = (X509Certificate2Collection)store.Certificates;
        X509Certificate2Collection fcollection = (X509Certificate2Collection)collection.Find(X509FindType.FindByTimeValid,DateTime.Now,false);
        X509Certificate2Collection scollection = X509Certificate2UI.SelectFromCollection(fcollection, "Test Certificate Select","Select a certificate from the following list to get information on that certificate",X509SelectionFlag.MultiSelection);
        Console.WriteLine("Number of certificates: {0}{1}",scollection.Count,Environment.NewLine);

        foreach (X509Certificate2 x509 in scollection)
        {
            try
            {
                byte[] rawdata = x509.RawData;
                Console.WriteLine("Content Type: {0}{1}",X509Certificate2.GetCertContentType(rawdata),Environment.NewLine);
                Console.WriteLine("Friendly Name: {0}{1}",x509.FriendlyName,Environment.NewLine);
                Console.WriteLine("Certificate Verified?: {0}{1}",x509.Verify(),Environment.NewLine);
                Console.WriteLine("Simple Name: {0}{1}",x509.GetNameInfo(X509NameType.SimpleName,true),Environment.NewLine);
                Console.WriteLine("Signature Algorithm: {0}{1}",x509.SignatureAlgorithm.FriendlyName,Environment.NewLine);
                Console.WriteLine("Public Key: {0}{1}",x509.PublicKey.Key.ToXmlString(false),Environment.NewLine);
                Console.WriteLine("Certificate Archived?: {0}{1}",x509.Archived,Environment.NewLine);
                Console.WriteLine("Length of Raw Data: {0}{1}",x509.RawData.Length,Environment.NewLine);
                X509Certificate2UI.DisplayCertificate(x509);
                x509.Reset();
            }
            catch (CryptographicException)
            {
                Console.WriteLine("Information could not be written out for this certificate.");
            }
        }
        store.Close();
    }
}

Remarks

The extensions defined in the X.509 v3 certificate format allow additional data to be included in the certificate. A number of extensions are defined by ISO in the X.509 v3 definition as well as by PKIX in RFC 3280, "Certificate and Certificate Revocation List (CRL) Profile." Common extensions include information regarding key usage (X509KeyUsageExtension), key identifiers (X509SubjectKeyIdentifierExtension), certificate policies, revocation information (CRL Distribution Point extension), and other uses.

Applies to