regex.replace does not working in pattern with "$" - c#

Question

I've tried to replace user name in Git's URL, by using Regex.replace().

The reason I want to use Regex.Replace instead of string.Replace is because I want to replace only the first occurrence.

The expected result is: "https://******:adss!#&@github.com/test/test.git" The actual result is: "https://#32$3:adss!#&@github.com/test/test.git"

Unfortunately it's not replaced. The code as bellow:

class Program
{
    private static Regex reg = new Regex(@"(?i)(http|https):\/\/(?<UserName>.*):(.*?)@.*\/");
    private const string userNameGroup = "UserName";

    static void Main(string[] args)
    {
        string url = matchRgexWithUserName("https://#32$3:adss!#&@github.com/test/test.git");

        Console.WriteLine(url);
    }

    static string matchRgexWithUserName(string url)
    {
        Match match = reg.Match(url.ToString());

        string username = match.Groups[userNameGroup].Value;
        Regex r = new Regex(username);
        url = r.Replace(url,"******",1);
        return url;
    }
}

this line works well:

string username = match.Groups[userNameGroup].Value;

the problem is with these lines:

Regex r = new Regex(username);
        url = r.Replace(url,"******",1);
        return url;

I suspect the problem is with the "$". Is there other way to overcome on it? Thanks!

Please, try regexstorm.net/tester before coding your regex. You can fix it there. — user1389591
– user1389591, Commented Dec 23, 2015 at 13:02
Any sample of expected input and output + the actual output that you get? — Ian
– Ian, Commented Dec 23, 2015 at 13:02
Sorry but it's not the same problem. My problem is to replace any user name (not hard-coded) from the url. I'll update my question to explain more the problem. — Roni
– Roni, Commented Dec 23, 2015 at 13:16
you can use this method to escape special characters in regex: msdn.microsoft.com/en-us/library/… — Arie
– Arie, Commented Dec 23, 2015 at 13:22

Jakub Lortz · Accepted Answer · 2015-12-23 13:31:46Z

1

It doesn't work, because $ is a special character in regex.

To solve the problem, you can put everything before UserName and after it into groups too:

Regex reg = new Regex(@"(?<firstPart>(?i)(http|https):\/\/)(?<UserName>.*)(?<secondPart>:(.*?)@.*\/)");

Then you can use Replace to combine firstPart, "******" and secondPart - without UserName:

string result = reg.Replace(url, "${firstPart}******${secondPart}");

Basically, you match the url to a {firstPart}{UserName}{secondPart} pattern and replace it with {firstPart}******{secondPart} (removing the UserName).

edited Dec 23, 2015 at 13:31

answered Dec 23, 2015 at 13:13

Jakub Lortz

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3 Comments

JLRishe Over a year ago

This won't work correctly if the ****** contains any dollar signs.

Jakub Lortz Over a year ago

@JLRishe "******" contains only *s - that's what the UserName group should be replaced with.

JLRishe Over a year ago

I was figuring that ****** was OP's way of hiding the actual value from us, but you might be right.

JLRishe · Accepted Answer · 2015-12-23 13:07:31Z

0

Using Regex.Replace that way is the wrong way to go about this. Once you know the username, you can use a regular string replace:

url = url.Replace("://" + username, "://" + "*****");

edited Dec 23, 2015 at 13:07

answered Dec 23, 2015 at 13:04

JLRishe

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1 Comment

Roni Over a year ago

but if your user name is same as some folder's name in the path that will be replaced too.

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