String function (regex?) to remove query string pair from url string

Question

Given the following example "strings":

somePage.aspx?id=20&name=brian&token=1234
somePage.aspx?id=20&token=1234&name=brian
somePage.aspx?token=1234&id=20&name=brian

I want to remove the name/value pair for token in all cases, so I am left with:

somePage.aspx?id=20&name=brian
somePage.aspx?id=20&name=brian
somePage.aspx?id=20&name=brian

Note: I cannot use the Uri class for various reason.

Is there a single regex or string function that can do this?

I cannot use the Uri class for various reason for example? — L.B
– L.B, Commented Jan 9, 2012 at 18:58
Could be in a class library where adding a System.Web reference is just too much bloat? I've come across that. — kamranicus
– kamranicus, Commented Jan 9, 2012 at 19:02
Forcing the inclusion of System.Web would cause his application to break for anyone who only has .Net 4.0 Client Profile installed (which is the default installation of .Net on many W7 machines), so it makes sense to avoid System.Web to reduce deployment problems. — ean5533
– ean5533, Commented Jan 9, 2012 at 19:10
@ean5533 - Uri is not in System.Web, it is in System - msdn.microsoft.com/en-us/library/system.uri.aspx — Alexei Levenkov
– Alexei Levenkov, Commented Jan 9, 2012 at 19:32
The reason I can't use the Uri class is because I am dealing with a combination of absolute paths and various relative paths ("../", /SomeFolder/, etc.) and being able to derive a true path may not be possible. — Brian David Berman
– Brian David Berman, Commented Jan 9, 2012 at 19:38

ean5533 · Accepted Answer · 2012-01-09 18:54:51Z

5

I think this will do it for you (haven't had a chance to test).

string s = "somePage.aspx?id=20&name=brian&token=1234";
s = Regex.Replace(s, @"(&token=[^&\s]+|token=[^&\s]+&?)", "");

Edit: Updated to correctly handle the case where token is the first pair.

answered Jan 9, 2012 at 18:54

ean5533

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5 Comments

ean5533 Over a year ago

@JosephSilber In the case where token was the first pair, it wouldn't remove the trailing & after token, so the resulting string would look like somePage.aspx?&id=20&name=brian

Joseph Silber Over a year ago

Correct. Which is why you should use this: token=[^&]+&?

kamranicus Over a year ago

PS. Make the regex static to avoid performance issues, especially considering this will probably be called multiple times in a request.

ean5533 Over a year ago

@JosephSilber Good idea, much more succinct. Post it as an answer, it's better than mine.

ean5533 Over a year ago

@JosephSilber I labored over that code for hours, but for you I'll allow it.

Jpsy · Accepted Answer · 2017-12-20 15:11:04Z

3

(\btoken=[^&]*&|[\?&]token=[^&]*$)

See https://regexr.com/3ia6k

This regexp removes the token param in all variations, including the variation where token is the only param:

somePage.aspx?token=1234

Explanation:

Part 1: \btoken=[^&]*&

...catches token including its value and a terminating &.
This part handles the following cases:

somePage.aspx?id=20&token=1234&name=brian
somePage.aspx?token=1234&id=20&name=brian

Part 2: [\?&]token=[^&]*$

...catches token when it appears as the last parameter and/or the only parameter, together with its leading ? or &.
This part handles the following cases:

somePage.aspx?id=20&name=brian&token=1234
somePage.aspx?token=1234

edited Dec 20, 2017 at 15:11

answered Jan 9, 2012 at 18:59

Jpsy

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2 Comments

yajiv Over a year ago

it will not pass case like "abc.com?token=123"

Jpsy Over a year ago

@yajiv: You are fully correct. Although your case has not been requested by the OP, it might be very relevant for many visitors of this question. I have updated my answer to handle all possible combinations. Also added a bit of explanation.

Alexei Levenkov · Accepted Answer · 2012-01-09 18:59:34Z

2

Consider using HttpUtility.ParseQueryString ( http://msdn.microsoft.com/en-us/library/ms150046.aspx ) to parse and UriBuilder to construct back...

Be careful with all encodings and ordering of parameters in query string - Uri class would helped with it.

answered Jan 9, 2012 at 18:59

Alexei Levenkov

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1 Comment

kamranicus Over a year ago

Sounds like he wants to avoid System.Web otherwise he probably would have just used new Uri(url).

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