using System;
using System.Configuration;
using System.Data;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Mail;
using System.Net.Mime;
using System.Security.Cryptography.Pkcs;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;


public partial class _Default : System.Web.UI.Page
{
  protected void Page_Load(object sender, EventArgs e)
  {


    SendMessage();

  }




  public void SendMessage()
  {
    encrypt(signed(buildMessageContent()));
  }

  public void encrypt(string content)
  {
    MailMessage message = new System.Net.Mail.MailMessage();
    string encryptedContentType = "application/x-pkcs7-mime; smime-type=enveloped-data; name=\"smime.p7m\"";
    string signatureBoundry2 = "--PTBoundry=3";
    StringBuilder fullUnencryptedMessageBuilder = new StringBuilder();
    fullUnencryptedMessageBuilder.Append("Content-Type: ");
    fullUnencryptedMessageBuilder.Append("multipart/signed; ");
    fullUnencryptedMessageBuilder.Append("boundary=\"");
    fullUnencryptedMessageBuilder.Append(signatureBoundry2);
    fullUnencryptedMessageBuilder.Append("\"; protocol=\"application/x-pkcs7-signature\"; micalg=SHA1; ");

    fullUnencryptedMessageBuilder.Append("\r\n");
    fullUnencryptedMessageBuilder.Append("Content-Transfer-Encoding: ");
    fullUnencryptedMessageBuilder.Append(TransferEncoding.SevenBit);
    fullUnencryptedMessageBuilder.Append("\r\n\r\n");
    fullUnencryptedMessageBuilder.Append(content);

    string fullUnencryptedMessage = fullUnencryptedMessageBuilder.ToString();

    byte[] encryptedBytes = DoEncrypt(fullUnencryptedMessage, GetCert());

    MemoryStream stream = new MemoryStream(encryptedBytes);
    AlternateView view = new AlternateView(stream, "application/pkcs7-mime; smime-type=signed-data;name=smime.p7m");
    view.TransferEncoding = TransferEncoding.Base64;
    message.AlternateViews.Add(view);
    message.To.Add("yourmail@yourdomain.com");

    message.From = new MailAddress("someone@yourdomain.com");
    message.Subject = "TEST";
    SmtpClient smtp = new SmtpClient("Smtp-relay.ip.nianet.dk");
    smtp.Send(message);


  }

  public byte[] DoEncrypt(string message, X509Certificate2 encryptionCertificates)
  {
    byte[] messageBytes = Encoding.ASCII.GetBytes(message);

    EnvelopedCms envelopedCms = new EnvelopedCms(new ContentInfo(messageBytes));

    CmsRecipient recipients = new CmsRecipient(SubjectIdentifierType.IssuerAndSerialNumber, encryptionCertificates);

    envelopedCms.Encrypt(recipients);

    return envelopedCms.Encode();
  }


  public string signed(string Content)
  {
    string signatureBoundry = "--PTBoundry=2";
    string signatureBoundry2 = "--PTBoundry=3";
    StringBuilder fullUnsignedMessageBuilder = new StringBuilder();

    fullUnsignedMessageBuilder.Append("Content-Type: ");
    fullUnsignedMessageBuilder.Append("multipart/mixed;");
    fullUnsignedMessageBuilder.Append(" boundary=\"");
    fullUnsignedMessageBuilder.Append(signatureBoundry);
    fullUnsignedMessageBuilder.Append("\"\r\n");
    fullUnsignedMessageBuilder.Append("Content-Transfer-Encoding: ");

    fullUnsignedMessageBuilder.Append("7bit");
    fullUnsignedMessageBuilder.Append("\r\n");
    fullUnsignedMessageBuilder.Append(Content);

    string fullUnsignedMessage = fullUnsignedMessageBuilder.ToString();

    byte[] signature = GetSignature(fullUnsignedMessage, GetCert(), GetCert());

    StringBuilder signedMessageBuilder = new StringBuilder();

    signedMessageBuilder.Append("--");
    signedMessageBuilder.Append(signatureBoundry2);
    signedMessageBuilder.Append("\r\n");
    signedMessageBuilder.Append(fullUnsignedMessage);
    signedMessageBuilder.Append("\r\n");
    signedMessageBuilder.Append("--");
    signedMessageBuilder.Append(signatureBoundry2);
    signedMessageBuilder.Append("\r\n");
    signedMessageBuilder.Append("Content-Type: application/x-pkcs7-signature; name=\"smime.p7s\"\r\n");
    signedMessageBuilder.Append("Content-Transfer-Encoding: base64\r\n");
    signedMessageBuilder.Append("Content-Disposition: attachment; filename=\"smime.p7s\"\r\n\r\n");
    signedMessageBuilder.Append(Convert.ToBase64String(signature));
    signedMessageBuilder.Append("\r\n\r\n");

    signedMessageBuilder.Append("--");
    signedMessageBuilder.Append(signatureBoundry2);
    signedMessageBuilder.Append("--\r\n");

    return signedMessageBuilder.ToString();
  }


  public byte[] GetSignature(string message, X509Certificate2 signingCertificate, X509Certificate2 encryptionCertificate)
  {
    byte[] messageBytes = Encoding.ASCII.GetBytes(message);

    SignedCms signedCms = new SignedCms(new ContentInfo(messageBytes), true);

    CmsSigner cmsSigner = new CmsSigner(SubjectIdentifierType.IssuerAndSerialNumber, signingCertificate);
    cmsSigner.IncludeOption = X509IncludeOption.WholeChain;

    if (encryptionCertificate != null)
    {
      cmsSigner.Certificates.Add(encryptionCertificate);
    }

    Pkcs9SigningTime signingTime = new Pkcs9SigningTime();
    cmsSigner.SignedAttributes.Add(signingTime);

    signedCms.ComputeSignature(cmsSigner, false);

    return signedCms.Encode();
  }


  public string buildMessageContent()
  {

    string messageBoundry = "--PTBoundry=2";
    StringBuilder message = new StringBuilder();

    message.Append("\r\n");
    message.Append("\r\n");
    message.Append("--");
    message.Append(messageBoundry + "\r\n");
    message.Append("Content-Type: text/html; charset=us-ascii\r\n");  //could use text/html as well here if you want a html message
    message.Append("Content-Transfer-Encoding: ");
    message.Append("quoted - printable");
    message.Append("\r\n\r\n");
    message.Append("TEST AF kryptering");//BODY TEXT GOES HERE
    message.Append("\r\n");

    //ADD file section
    //could be filename or whatever
    //foreach (string filename in attachments){ 
    //Read file part implement your own 

    byte[] buff = null;
    FileStream fs = new FileStream("c:\\snebaer.jpg", FileMode.Open, FileAccess.Read);
    BinaryReader br = new BinaryReader(fs);
    long numBytes = new FileInfo("c:\\snebaer.jpg").Length;
    buff = br.ReadBytes((int)numBytes);

    byte[] bytes = buff;
    //Setup filecontent 
    String filecontent =
     Convert.ToBase64String(bytes,
                          Base64FormattingOptions.InsertLineBreaks);

    message.Append("--");
    message.Append(messageBoundry);
    message.Append("\r\n");
    message.Append("Content-Type: ");
    message.Append("application/octet-stream;");
    message.Append("name=c:\\snebaer.jpg");
    message.Append("\r\n");
    message.Append("Content-Transfer-Encoding: base64\r\n\r\n");
    message.Append(filecontent);
    message.Append("\r\n\r\n");
    //}

    //END FILSECTION


    message.Append("--");
    message.Append(messageBoundry);
    message.Append("--\r\n");


    return message.ToString();
  }


  public static X509Certificate2 GetCert()
  {
    //Sets up a new store to look for at certificat in.
    X509Store localStore = new X509Store(StoreName.My, StoreLocation.LocalMachine);
    localStore.Open(OpenFlags.ReadOnly | OpenFlags.OpenExistingOnly);

    try
    {
      //NOTE FALSE IS ONLY USED FOR TESTS SHOULD BE CHANGED TO true<br>
      X509Certificate2Collection matches =
      localStore.Certificates.Find(X509FindType.FindBySerialNumber, "a0 51 bf 0a bc 4a 11 8b 41 9d 56 47 92 b2 34 6c", false);
      if (matches.Count > 0)
      {
        return matches[0];
      }
      else
      {
        return null;
      }
    }
    finally
    {
      localStore.Close();
    }

  }
}