C# - regex finding all ascii enclosed in ' ' and convert them to hex ascii output

Question

I write a converter for user input data, which converts number value strings and ascii characters enclosed in ' ' to hex representation. Number entering works fine with:

string TestText = "lorem, 'C', 127, 0x06, '#' ipsum";
TestText = Regex.Replace(
    TestText, 
    " +\\d{1,3}", 
    (MatchEvaluator)(match => Convert.ToByte(match.Value).ToString("X2")));         
Out.Text = TestText;

But how can I detect ascii chars enclosed in ' ' and convert them to a hex string like: 'C' will be 43 and '+' becomes 2B.

You don't need to explicitly cast your lambda with `(MatchEvaluator)` — juharr, Mar 15 '16 at 11:58
Personally I do not know C#, but using what you have asked to do a quick search in the stack overflow questions, I found these two questions with accepted answers here. [Converting Numbers between hex and dec in C#](http://stackoverflow.com/questions/74148/how-to-convert-numbers-between-hexadecimal-and-decimal-in-c) AND [Getting the ascii value of a character in C#](http://stackoverflow.com/questions/5002909/getting-the-ascii-value-of-a-character-in-a-c-sharp-string) Both have accepted answers, both should help you with your problem. — KyleFairns, Mar 15 '16 at 12:00

score 0 · Answer 1 · answered Mar 15 '16 at 11:56

0

Basically, you want to match the regular expression '[^']'. This looks for all characters that are not ' but which are enclosed in '.

Then, in your match evaluator, you get the character in the middle, and convert it to a hexadecimal string. To do that, first cast the char to an int and then you can use ToString("x2"):

TestText = Regex.Replace(TestText, "'[^']'",
    (MatchEvaluator)(match => ((int)match.Value[1]).ToString("x2")));

answered Mar 15 '16 at 11:56

poke

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Should this not be '[^']+' As your example will only match a single character between apostrophes. – Rohaq Mar 15 '16 at 12:59
@Rohaq I am under the impression that that is the desired result. – poke Mar 15 '16 at 13:05

score 0 · Answer 2 · answered Mar 15 '16 at 11:58

First, you need a RegEx to capture the character inside the 's: "'(.)'"

Then you need to convert that character to its hex equivalent, like so: Encoding.ASCII.GetBytes(match.Groups[1].Value).First().ToString("X2")

so your final code would look like this:

string TestText = "lorem, 'C', 127, 0x06, '#' ipsum '+'";
TestText = Regex.Replace(TestText, @" +\d{1,3}", match => Convert.ToByte(match.Value).ToString("X2"));         
TestText = Regex.Replace(TestText, "'(.)'", match => Encoding.ASCII.GetBytes(match.Groups[1].Value).First().ToString("X2"));
Out.Text = TestText;

Note that, as pointed out in the comments, your RegEx is currently matching the 0 at the beginning of 0x06, which may not be what you want.

C# - regex finding all ascii enclosed in ' ' and convert them to hex ascii output

2 Answers2