How to convert a string containing escape characters to a string

Question

I have a string that is returned to me which contains escape characters.

Here is a sample string

"test\40gmail.com"

As you can see it contains escape characters. I need it to be converted to its real value which is

"test@gmail.com"

How can I do this?

Is this the only case, or are there many different control characters that you'll have to account for? — Jason Down, Jul 20 '12 at 17:27
Are you working in a web environment? (i.e. do you already have a reference to System.Web in your project). Or do you need something that is independent? — James, Jul 20 '12 at 17:31
Both HttpUtility and WebUtility have decoding methods - please reference this https://stackoverflow.com/questions/122641/how-can-i-decode-html-characters-in-c — Mike Perrenoud, Jul 20 '12 at 17:30

score 10 · Accepted Answer · edited Jun 23 '15 at 11:29

10

If you are looking to replace all escaped character codes, not only the code for @, you can use this snippet of code to do the conversion:

public static string UnescapeCodes(string src) {
    var rx = new Regex("\\\\([0-9A-Fa-f]+)");
    var res = new StringBuilder();
    var pos = 0;
    foreach (Match m in rx.Matches(src)) {
        res.Append(src.Substring(pos, m.Index - pos));
        pos = m.Index + m.Length;
        res.Append((char)Convert.ToInt32(m.Groups[1].ToString(), 16));
    }
    res.Append(src.Substring(pos));
    return res.ToString();
}

The code relies on a regular expression to find all sequences of hex digits, converting them to int, and casting the resultant value to a char.

edited Jun 23 '15 at 11:29

Gianluca Ghettini

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answered Jul 20 '12 at 17:44

Sergey Kalinichenko

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I'm a little confused with regex and C# (so many escape characters). Could you possibly post the regex string by itself (not formatted for C# use)? – James Jul 20 '12 at 17:53
@James Sure, it's `\\([0-9A-Fa-f]+)` (here, the slash is escaped for the regex engine, but not for the compiler). – Sergey Kalinichenko Jul 20 '12 at 17:55
It's handy when working with regexes to use a C# "verbatim string literal".. e.g. `var rx = new Regex(@"\\([0-9A-Fa-f]+)");` – Dominic Cronin Apr 16 '14 at 10:02
res.Append(src.Substring(pos, m.Index)); should be res.Append(src.Substring(pos, m.Index - pos)); – Gianluca Ghettini Jun 23 '15 at 11:26

score 1 · Answer 2 · answered Jun 21 '22 at 20:57

1

.NET provides the static methods Regex.Unescape and Regex.Escape to perform this task and back again. Regex.Unescape will do what you need.

https://learn.microsoft.com/en-us/dotnet/api/system.text.regularexpressions.regex.unescape

answered Jun 21 '22 at 20:57

Ben Gripka

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Micah Armantrout · Answer 3 · 2012-07-20T18:07:11.323

0

string test = "test\40gmail.com";

test.replace(@"\40","@");

If you want a more general approach ...

HTML Decode

edited Jul 20 '12 at 18:07

answered Jul 20 '12 at 17:26

Micah Armantrout

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please explain how it would not – Micah Armantrout Jul 20 '12 at 17:27
he probably saw your previous answer prior to the edit.. your answer will work Micah – MethodMan Jul 20 '12 at 17:28
1

When I first saw it, it had `test.replace("\40","");`, and @dasblinkenlight's commment would be true. – crashmstr Jul 20 '12 at 17:28
You need `@"\40"` (same with `test`'s declaration) so that C# takes it verbatim. – Tim S. Jul 20 '12 at 17:42
1

I downvoted this because the answer applies only to the sample string, and not to the general case. – Ryan Kohn Jul 20 '12 at 18:02

Esoteric Screen Name · Answer 4 · 2012-07-20T18:48:24.147

0

The sample string provided ("test\40gmail.com") is JID escaped. It is not malformed, and HttpUtility/WebUtility will not correctly handle this escaping scheme.

You can certainly do it with string or regex functions, as suggested in the answers from dasblinkenlight and C.Barlow. This is probably the cleanest way to achieve the desired result. I'm not aware of any .NET libraries for decoding JID escaping, and a brief search hasn't turned up much. Here is a link to some source which may be useful, though.

edited Jul 20 '12 at 18:48

answered Jul 20 '12 at 18:07

Esoteric Screen Name

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You are assuming that he is using Jabber / chat client when this is not stated – Micah Armantrout Jul 20 '12 at 18:22
@MicahArmantrout No, I'm not. I didn't say he was using that client, I said he has strings escaped in the same fashion. Using `\(hex value)` to indicate an escaped character is not platform dependent. – Esoteric Screen Name Jul 20 '12 at 18:41
@MicahArmantrout No. I am absolutely not making that assumption. – Esoteric Screen Name Jul 20 '12 at 18:42

Willie Visagie · Answer 5 · 2017-10-05T12:28:17.583

I just wrote this piece of code and it seems to work beautifully... It requires that the escape sequence is in HEX, and is valid for value's 0x00 to 0xFF.

// Example
str = remEscChars(@"Test\x0D") // str = "Test\r"

Here is the code.

private string remEscChars(string str)
{
   int pos = 0;
   string subStr = null;
   string escStr = null;

   try
   {
      while ((pos = str.IndexOf(@"\x")) >= 0)
      {
         subStr = str.Substring(pos + 2, 2);
         escStr = Convert.ToString(Convert.ToChar(Convert.ToInt32(subStr, 16)));
         str = str.Replace(@"\x" + subStr, escStr);
      }
   }
   catch (Exception ex)
   {
      throw ex;
   }

   return str;
}

How to convert a string containing escape characters to a string

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