How to convert Quoted-Print String

Question

I'm working on French String in .NET Decoding a Mail body , I receive "Chasn=C3=A9 sur illet" I would like to get "Chasné sur illet" and i don't find any solution aver 2 days web search.

C# ou VB.NET Can anyone helps me ?

thanks

Answer 1

Or the easiest of all, just use the QuotedPrintableDecoder from my MimeKit library:

static string DecodeQuotedPrintable (string input, string charset)
{
    var decoder = new QuotedPrintableDecoder ();
    var buffer = Encoding.ASCII.GetBytes (input);
    var output = new byte[decoder.EstimateOutputLength (buffer.Length)];
    int used = decoder.Decode (buffer, 0, buffer.Length, output);
    var encoding = Encoding.GetEncoding (charset);
    return encoding.GetString (output, 0, used);
}

Note that the other answers above assume the decoded content will be ASCII or UTF-8, but that isn't necessarily the case. You'll need to get the charset parameter from the Content-Type header of the MIME part that you are decoding.

Of course... if you don't know how to get that info, you could simply use my awesome MailKit library to get the MIME part from IMAP and have it do all of this work for you.

Answer 2

This is UTF8 encoding.

Using this post:

http://www.dpit.co.uk/decoding-quoted-printable-email-in-c/

Here is the code (don't forget to accept the answer if helped):

using System;
using System.Text;
using System.Text.RegularExpressions;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {

            Console.WriteLine(DecodeQuotedPrintable("Chasn=C3=A9 sur illet"));
            Console.ReadKey();
        }

        static string DecodeQuotedPrintable(string input)
        {
            var occurences = new Regex(@"(=[0-9A-Z][0-9A-Z])+", RegexOptions.Multiline);
            var matches = occurences.Matches(input);
            foreach (Match m in matches)
            {
                byte[] bytes = new byte[m.Value.Length / 3];
                for (int i = 0; i < bytes.Length; i++)
                {
                    string hex = m.Value.Substring(i * 3 + 1, 2);
                    int iHex = Convert.ToInt32(hex, 16);
                    bytes[i] = Convert.ToByte(iHex);
                }
                input = input.Replace(m.Value, Encoding.UTF8.GetString(bytes));
            }
            return input.Replace("=rn", "");
        }
    }
}

Answer 3

From : https://stackoverflow.com/a/36803911/6403521 My solution :

    [TestMethod]
    public void TestMethod1()
    {

        Assert.AreEqual("La Bouichère", quotedprintable("La Bouich=C3=A8re", "utf-8"));
        Assert.AreEqual("Chasné sur illet", quotedprintable("Chasn=C3=A9 sur illet", "utf-8"));
        Assert.AreEqual("é è", quotedprintable("=C3=A9 =C3=A8", "utf-8"));
    }
    private string quotedprintable(string pStrIn, string encoding)
    {
        String strOut = pStrIn.Replace("=\r\n", "");
        // Find the first =
        int position = strOut.IndexOf("=");
        while (position != -1)
        { 
            // String before the =
            string leftpart = strOut.Substring(0, position);
            // get the QuotedPrintable String in a ArrayList
            System.Collections.ArrayList hex = new System.Collections.ArrayList();
            // The first Part
            hex.Add(strOut.Substring(1 + position, 2));
            // Look for the next parts
            while (position + 3 < strOut.Length && strOut.Substring(position + 3, 1) == "=")
            {
                position = position + 3;
                hex.Add(strOut.Substring(1 + position, 2));
            }
            // In the hex Array, we have two items 
            // Convert using the GetEncoding Function
            byte[] bytes = new byte[hex.Count];
            for (int i = 0; i < hex.Count; i++)
            {
                bytes[i] = System.Convert.ToByte(new string(((string)hex[i]).ToCharArray()), 16);
            }
            string equivalent = System.Text.Encoding.GetEncoding(encoding).GetString(bytes);
            // Part of the orignal String after the last QP Symbol
            string rightpart = strOut.Substring(position + 3);
            // Re build the String
            strOut = leftpart + equivalent + rightpart;
            // find the new QP Position
            position = leftpart.Length + equivalent.Length;
            if (rightpart.Length == 0)
            {
                position = -1;
            }
            else
            {
                position = strOut.IndexOf("=", position + 1);
            }
        }
        return strOut;
    }

Answer 4

We had an issue with this method - that it is VERY slow. The following enhanced performance A LOT

public static string FromMailTransferEncoding(this string messageText, Encoding enc, string transferEncoding)
{
    if (string.IsNullOrEmpty(transferEncoding)) 
        return messageText;

    if ("quoted-printable".Equals(transferEncoding.ToLower())) 
    {
        StringBuilder sb = new StringBuilder();               
        string delimitorRegEx = @"=[\r][\n]";
        string[] parts = Regex.Split(messageText, delimitorRegEx);

        foreach (string part in parts)
        {
            string subPart = part;
            Regex occurences = new Regex(@"(=[0-9A-Z][0-9A-Z])+", RegexOptions.Multiline);
            MatchCollection matches = occurences.Matches(subPart);

            foreach (Match m in matches)
            {
                byte[] bytes = new byte[m.Value.Length / 3];
                for (int i = 0; i < bytes.Length; i++)
                {
                    string hex = m.Value.Substring(i * 3 + 1, 2);
                    int iHex = Convert.ToInt32(hex, 16);
                    bytes[i] = Convert.ToByte(iHex);
                }

                subPart = occurences.Replace(subPart, enc.GetString(bytes), 1);
            }

            sb.Append(subPart);
        }
        return sb.ToString();
    }        
return messageText;
}

Answer 5

    static string ConverFromHex(string source)
    {
        string target = string.Empty;

        int startPos = source.IndexOf('=', 0);
        int prevStartPos = 0;
        while (startPos >= 0)
        {
            // concat with substring from source
            target += source.Substring(prevStartPos, startPos - prevStartPos);

            // next offset
            startPos++;

            // update prev pos
            prevStartPos = startPos;

            // get substring
            string hexString = source.Substring(startPos, 2);

            // get int equiv
            int hexNum = 0;
            if (int.TryParse(hexString, System.Globalization.NumberStyles.AllowHexSpecifier, System.Globalization.CultureInfo.InvariantCulture, out hexNum))
            {
                // add to target string
                target += (char)hexNum;

                // add hex length
                prevStartPos += 2;
            }

            // next occurence
            startPos = source.IndexOf('=', startPos);
        }

        // add rest of source
        target += source.Substring(prevStartPos);

        return target;
    }