X509KeyUsageExtension Class

Definition

Namespace:

System.Security.Cryptography.X509Certificates

Assemblies:

netstandard.dll, System.Security.Cryptography.dll

Source:

X509KeyUsageExtension.cs

Defines the usage of a key contained within an X.509 certificate. This class cannot be inherited.

C#

public sealed class X509KeyUsageExtension : System.Security.Cryptography.X509Certificates.X509Extension

Inheritance

Object

AsnEncodedData

X509Extension

X509KeyUsageExtension

Examples

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.

C#

using System;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;

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

            X509Certificate2Collection collection = (X509Certificate2Collection)store.Certificates;
            for (int i = 0; i < collection.Count; i++)
            {
                foreach (X509Extension extension in collection[i].Extensions)
                {
                    Console.WriteLine(extension.Oid.FriendlyName + "(" + extension.Oid.Value + ")");

                    if (extension.Oid.FriendlyName == "Key Usage")
                    {
                        X509KeyUsageExtension ext = (X509KeyUsageExtension)extension;
                        Console.WriteLine(ext.KeyUsages);
                    }

                    if (extension.Oid.FriendlyName == "Basic Constraints")
                    {
                        X509BasicConstraintsExtension ext = (X509BasicConstraintsExtension)extension;
                        Console.WriteLine(ext.CertificateAuthority);
                        Console.WriteLine(ext.HasPathLengthConstraint);
                        Console.WriteLine(ext.PathLengthConstraint);
                    }

                    if (extension.Oid.FriendlyName == "Subject Key Identifier")
                    {
                        X509SubjectKeyIdentifierExtension ext = (X509SubjectKeyIdentifierExtension)extension;
                        Console.WriteLine(ext.SubjectKeyIdentifier);
                    }

                    if (extension.Oid.FriendlyName == "Enhanced Key Usage")
                    {
                        X509EnhancedKeyUsageExtension ext = (X509EnhancedKeyUsageExtension)extension;
                        OidCollection oids = ext.EnhancedKeyUsages;
                        foreach (Oid oid in oids)
                        {
                            Console.WriteLine(oid.FriendlyName + "(" + oid.Value + ")");
                        }
                    }
                }
            }
            store.Close();
        }
        catch (CryptographicException)
        {
            Console.WriteLine("Information could not be written out for this certificate.");
        }
    }
}

Remarks

The X509KeyUsageExtension class uses the flags in the X509KeyUsageFlags enumeration to define or determine key usage.

Constructors

X509KeyUsageExtension()	Initializes a new instance of the X509KeyUsageExtension class.
X509KeyUsageExtension(AsnEncodedData, Boolean)	Initializes a new instance of the X509KeyUsageExtension class using an AsnEncodedData object and a value that identifies whether the extension is critical.
X509KeyUsageExtension(X509KeyUsageFlags, Boolean)	Initializes a new instance of the X509KeyUsageExtension class using the specified X509KeyUsageFlags value and a value that identifies whether the extension is critical.

Properties

Critical	Gets a Boolean value indicating whether the extension is critical. (Inherited from X509Extension)
KeyUsages	Gets the key usage flag associated with the certificate.
Oid	Gets or sets the Oid value for an AsnEncodedData object. (Inherited from AsnEncodedData)
RawData	Gets or sets the Abstract Syntax Notation One (ASN.1)-encoded data represented in a byte array. (Inherited from AsnEncodedData)

Methods

CopyFrom(AsnEncodedData)	Initializes a new instance of the X509KeyUsageExtension class using an AsnEncodedData object.
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
Format(Boolean)	Returns a formatted version of the Abstract Syntax Notation One (ASN.1)-encoded data as a string. (Inherited from AsnEncodedData)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetType()	Gets the Type of the current instance. (Inherited from Object)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
ToString()	Returns a string that represents the current object. (Inherited from Object)

Applies to