Replacing digits in C# string

Question

I am trying to use regular expressions to do some work on strings but I am having some difficulty. My goal is to replace numbers in a string with a character, specifically if there is a group of numbers in the string I want to replace the entire group of numbers with a *. If there is just a single digit I want to replace that with a ?.

For example, if I had the string "test12345.txt" I would like to turn that to "test*.txt", but if I have "test1.txt" I would like to turn that to just "test?.txt".

I tried

Regex r = new Regex(@"\d+", RegexOptions.None);
returnString = r.Replace(returnString, "*");

But this replaces replaces even a single digit on its own with a *

Regex r = new Regex(@"\d+", RegexOptions.None); returnString = r.Replace(returnString, "*"); But this replaces replaces even a single digit on its own with a * — DukeOfMarmalade
– DukeOfMarmalade, Commented Dec 21, 2011 at 8:36
@Jim, you have to use two regexes for your problem, see below — fge
– fge, Commented Dec 21, 2011 at 8:38

IanNorton · Accepted Answer · 2011-12-21 08:36:58Z

24

This is pretty easy with Regex.Replace

string input = "test12345.txt";

// replace all numbers with a single *
string replacedstar = Regex.Replace( input, "[0-9]{2,}", "*" );

// replace remaining single digits with ?
string replacedqm = Regex.Replace( input, "[0-9]", "?" );

answered Dec 21, 2011 at 8:36

IanNorton

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2 Comments

Jason Dias Over a year ago

Is there a way to replace this all numbers with * at each position ? eg. input: test1234 results in: test**** Thanks in advance

Galacticai Over a year ago

[0-9] does not cover other languages, \d is recommended for global contexts since it checks for other languages' digits too

Abdul Munim · Accepted Answer · 2011-12-21 08:42:19Z

4

This will do, first it will match more than two digits and replace the complete block with * and the 2nd statement is for if there's single digit, it will replace with ?'

var newFileName = Regex.Replace(fileName, @"\d{2,}", "*");
newFileName = Regex.Replace(fileName, @"\d", "?");

Hope this helps.

answered Dec 21, 2011 at 8:42

Abdul Munim

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Comments

fge · Accepted Answer · 2011-12-21 08:36:37Z

2

Do this with two regexes:

replace \d{2,} with *,
replace \d with ?.

answered Dec 21, 2011 at 8:36

fge

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Comments

Muhammad Hasan Khan · Accepted Answer · 2011-12-21 09:41:57Z

2

    static string ReplaceNumbers(string text)
    {
        string output = Regex.Replace(text, @"\d{2,}", "*");
        output = Regex.Replace(output, @"\d", "?");
        return output;
    }

\d is for digit
{2,} means at least 2 digits with no max limit

edited Dec 21, 2011 at 9:41

answered Dec 21, 2011 at 8:36

Muhammad Hasan Khan

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2 Comments

jb. Over a year ago

Does \d{1,1} ensure that there is only one digit? Or would it still match "2" from the string "23"? If not, what's the difference between \d{1,1} and just \d ?

Muhammad Hasan Khan Over a year ago

@jb there is no difference between \d{1,1} and \d

sharuk badsha · Accepted Answer · 2020-02-04 12:52:11Z

0

        int n1 = Convert.ToInt32(number.Text);
        int n2 = Convert.ToInt32(replace.Text);
        int n3 = Convert.ToInt32(othernumber.Text);
        int temp;
        int result = 0;
        int i = 1;
        while (n1 > 0)
        {
            temp = n1 % 10;
            if (n2 == temp)
            {
                result += n3 * i;
            }
            else
            {
                result = result + temp * i;
            }
            i *= 10;
            n1 = n1 / 10;
        }
        afterswap.Text = Convert.ToString(result);

answered Feb 4, 2020 at 12:52

sharuk badsha

1

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