/// <summary>
/// Extract issuer alternative name is available.
/// </summary>
/// <returns>Issuer alternative name or null.</returns>
protected GeneralNames GetIssuerAlternativeName()
{
Asn1OctetString extensionValue = Issuer?.GetExtensionValue(new DerObjectIdentifier(X509Extensions.SubjectAlternativeName.Id));
return(extensionValue == null ? null : GeneralNames.GetInstance(X509ExtensionUtilities.FromExtensionValue(extensionValue)));
}