Wednesday, February 22, 2017

How to send encrypted mail in C#

It was a request of one of my client to send the mail as encrypted so that this kept secure while sending to customers. So after a search I found Jason Niver's code to be very handy to use. So I am sharing this will all so next time it becomes little bit easy to get.
using System;
using System.Text;
using System.Net.Mail;
using System.IO;
using System.Security.Cryptography.Pkcs;
using System.Security.Cryptography.X509Certificates;
namespace CommonUtilities
    //requires reference to System.Security
    class EmailUtil
        public static void SendEncryptedEmail(string[] to, string from, string subject, string body, string[] attachments)
            MailMessage message = new MailMessage();
            message.From = new MailAddress(from);
            message.Subject = subject;
            if (attachments != null && attachments.Length > 0)
                StringBuilder buffer = new StringBuilder();
                buffer.Append("MIME-Version: 1.0\r\n");
                buffer.Append("Content-Type: multipart/mixed; boundary=unique-boundary-1\r\n");
                buffer.Append("This is a multi-part message in MIME format.\r\n");
                buffer.Append("Content-Type: text/plain\r\n");  //could use text/html as well here if you want a html message
                buffer.Append("Content-Transfer-Encoding: 7Bit\r\n\r\n");
                if (!body.EndsWith("\r\n"))
                foreach (string filename in attachments)
                    FileInfo fileInfo = new FileInfo(filename);
                    buffer.Append("Content-Type: application/octet-stream; file=" + fileInfo.Name + "\r\n");
                    buffer.Append("Content-Transfer-Encoding: base64\r\n");
                    buffer.Append("Content-Disposition: attachment; filename=" + fileInfo.Name + "\r\n");
                    byte[] binaryData = File.ReadAllBytes(filename);
                    string base64Value = Convert.ToBase64String(binaryData, 0, binaryData.Length);
                    int position = 0;
                    while (position < base64Value.Length)
                        int chunkSize = 100;
                        if (base64Value.Length - (position + chunkSize) < 0)
                            chunkSize = base64Value.Length - position;
                        buffer.Append(base64Value.Substring(position, chunkSize));
                        position += chunkSize;
                body = buffer.ToString();
                body = "Content-Type: text/plain\r\nContent-Transfer-Encoding: 7Bit\r\n\r\n" + body;
            byte[] messageData = Encoding.ASCII.GetBytes(body);
            ContentInfo content = new ContentInfo(messageData);
            EnvelopedCms envelopedCms = new EnvelopedCms(content);
            CmsRecipientCollection toCollection = new CmsRecipientCollection();
            foreach (string address in to)
                message.To.Add(new MailAddress(address));
                X509Certificate2 certificate = null; //Need to load from store or from file the client's cert
                CmsRecipient recipient = new CmsRecipient(SubjectIdentifierType.SubjectKeyIdentifier, certificate);
            byte[] encryptedBytes = envelopedCms.Encode();
            //add digital signature:
            SignedCms signedCms = new SignedCms(new ContentInfo(encryptedBytes));
            X509Certificate2 signerCertificate = null; //Need to load from store or from file the signer's cert
            CmsSigner signer = new CmsSigner(SubjectIdentifierType.SubjectKeyIdentifier, signerCertificate);
            encryptedBytes = signedCms.Encode();
            //end digital signature section
            MemoryStream stream = new MemoryStream(encryptedBytes);
            AlternateView view = new AlternateView(stream, "application/pkcs7-mime; smime-type=signed-data;name=smime.p7m");
            SmtpClient client = new SmtpClient("your.smtp.mailhost");
            //add authentication info if required by your smtp server etc...
            //client.Credentials = CredentialCache.DefaultCredentials;

Now its time to install the certificate, for this go with the bellow codes.

using System.Security.Cryptography.X509Certificates;
private X509Certificate GetCertificate()
    X509Store store = new X509Store(StoreName.My, StoreLocation.LocalMachine);
    X509Certificate2Collection certs = store.Certificates.Find(X509FindType.FindBySerialNumber, “123456”, true);
    return certs[0];

1. Sending encrypted mail
2. Using certificates from the Windows certificate store

best practice to replace in C#

In most of the application we have to replace a string with some value and sometimes it has to be used multiple times for multiple characters. Like first replace the dot(.) and then hyphen(-) and then some other characters. by using String.Replace(String,String) method we can easily replace one characters or we can use regular expression to replace the characters or stings.

So for one character replacement there we can use only one String.Replace(String, String) by passing the new and old characters. But when we have to replace multiple characters then what is the best way to do? Lets see.

We can do this in two ways.

1. Using multiple Replace() method:

string demo = "This, is. my-text/ Remove, all= unwanted characters.";
// not a good practice
demo = demo.Replace(",", "");
demo = demo.Replace("/", "");
demo = demo.Replace("=", "");

This way you can replace the characters but there is a better way to do this.

// best practice
demo = demo.Replace(",", "").
            Replace("/", "").
            Replace("=", "");

Now this piece of code will save both time and space complexity to replace the desired characters.

2. Using Regular expression:

For multiple characters we can use regular expression to matching the string content and then replace the characters with the new values.

Let us took the previous example where we have to replace ",", "/" & "=" with blank value. So, our regular expression will be something like this. 

And the code will be like
Regex rgx = new Regex(@"[,/=]");
demo = rgx.Replace(demo, ""); 
Matches any lowercase ASCII letter.
We only need to match words with lowercase first letters.
This is a character range expression.
Word break:
Matches where a word starts.
Word characters:
Matches must have one or more characters.
Replace new line with new value.

Tuesday, February 14, 2017


This <noscript> tag defines the enable of javaScript in your browser. To state whether JavaScript is enabled or not in your browser we can use this tag. This works fully independently, means no other JavaScript or JQuery library are not needed to use this facility.

First create a HTML page with JavaScript functionality and a noscript tag.

<!DOCTYPE html>
<html xmlns="">
    <title>NoScript Example</title>
        Javascript is either disabled or not supported in your browser.
        Please enable it or use a Javascript enabled browser.
        This is a HTML page.
        alert('JavaScript is working!');

Now run the HTML page in browser and HTML content will display followed by a pop up showing "JavaScript is working".

Notice the text within noscript is not showing in the browser. Now disable the JavaScript in browser.
For Chrome go to Advance Settings->Privacy->Content Settings->JavaScript and select "Do not allow any site to run JavaScript". Hit OK and refresh the page.

Now you can see the text within nosript tag and notice no popup will be there as you disabled the JavaScript.

For Mozilla visit this link, and for Internet Explorer visit this link

Browser Dependency:
This HTML tag supports all the front line browsers like,
  • Chrome
  • Android
  • Firefox
  • Firefox Mobile
  • Internet Explorer (IE)
  • IE Phone
  • Opera
  • Opera Mobile
  • Safari
  • Safari Mobile

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