How do you parse the Subject Alternate Names from an X509Certificate2?

Question

Is there an easy way to get the Subject Alternate Names from an X509Certificate2 object?

        foreach (X509Extension ext in certificate.Extensions)
               


        

Answer 1

Expanding on Minh Nguyen's Answer taking into account using OID i rewrote it as a extension

namespace MyExtensions
{
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Security.Cryptography;
    using System.Security.Cryptography.X509Certificates;
    using System.Text.RegularExpressions;

    public static class X509Certificate2Extensions
    {
        private const string SubjectAlternateNameOID = "2.5.29.17";

        public static List SubjectAlternativeNames(this X509Certificate2 cert)
        {
            var subjectAlternativeName = cert.Extensions.Cast()
                .Where(n => n.Oid.Value == X509Certificate2Extensions.SubjectAlternateNameOID)
                .Select(n => new AsnEncodedData(n.Oid, n.RawData))
                .Select(n => n.Format(true))
                .FirstOrDefault();

            return string.IsNullOrWhiteSpace(subjectAlternativeName)
                ? new List()
                : subjectAlternativeName.Split(new[] {"\r\n", "\r", "\n"}, StringSplitOptions.RemoveEmptyEntries)
                    .Select(n => Regex.Match(n, @"^DNS Name=(.+)"))
                    .Where(r => r.Success && !string.IsNullOrWhiteSpace(r.Groups[1].Value))
                    .Select(r => r.Groups[1].Value)
                    .ToList();
        }
    }
}