How can I replace ending of a string using regex?

Question

I have a string "http://www.something.com/test/?pt=12"

I want to replace pt=12 by pt=13 using regex.

The string after replace will be : "http://www.something.com/test/?pt=13"

How can I achieve this in C#?

You could just use the String.Replace() method: myStr.Replace("pt=12", "pt=13"). — Spencer Wieczorek
– Spencer Wieczorek, Commented Jul 30, 2015 at 5:45
Spencer - I know the string.replace but actual requirmwent is quite complex.. I need a regex only. It's not a simple string replace. — Gurucharan Balakuntla Maheshku
– Gurucharan Balakuntla Maheshku, Commented Jul 30, 2015 at 6:17
If my answer was the answer you were looking for, could you please give it a check. thanks :) — Ralph
– Ralph, Commented Jul 30, 2015 at 22:50

Ralph · Accepted Answer · 2015-07-30 06:07:56Z

1

string result = "";
Regex reg = new Regex("(.*)(pt=12)");
Match regexMatch = reg.Match("http://www.something.com/test/?pt=12");
if(regexMatch.Success){
    result = regexMatch.Groups[1].Value + "pt=13"
}

answered Jul 30, 2015 at 6:07

Ralph

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Wiktor Stribiżew · Accepted Answer · 2015-07-30 13:43:55Z

1

I suppose you know the pt= part. I also presume that the param value is a number.

Then, you can use the following regex replacement:

var newval = 13;
var res = Regex.Replace(str, @"\?pt=[0-9]+", string.Format("?pt={0}", newval));

If the param can be non-first in the query string, replace \? with [?&].

Note that you could use the System.UriBuilder class. It has a Query property that you can use to rebuild the query string.

answered Jul 30, 2015 at 13:43

Wiktor Stribiżew

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