PRB： x509 证书支持仅 DER 编码证书

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

namespace ReadBase64Cert
{
    public class ReadBase64Cert
    {
        public ReadBase64Cert()
        {
        }
        public static void Main(string[] args)
        {
            if (args.Length < 1)
            {
                Console.WriteLine("Usage: Base64EncodedFile (.cer)\n");
                return;
            }

            // args[0] - Base64Encoded .cer file

            // Open the certificate, and read it into a byte array.
            FileStream certFile = new FileStream(args[0],
                FileMode.Open,
                FileAccess.Read);
            int size = (int)certFile.Length;
            byte[] certBytes = new byte[size];
            size = certFile.Read(certBytes, 0, size);
            certFile.Close();
    
            // Remove the unnecessary characters.
            String certString = Encoding.ASCII.GetString(certBytes);
            StringBuilder sb = new StringBuilder(certString);
            sb.Replace("-----BEGIN CERTIFICATE-----", "");
            sb.Replace("-----END CERTIFICATE-----", "");
    
            // Decode the bytes from base64 to raw bytes.
            certBytes = Convert.FromBase64String(sb.ToString());
            X509Certificate cert = new X509Certificate(certBytes);
            Console.WriteLine(cert.GetName()); 
        }
    }
}