A string replacement question with C#

Question

How do I remove string in bold within following url where q= is fixed parameter?

http://abc.com/qwe.aspx?q=DIEYeGJgNwvPSJ32ic1sY5x1ZYjOZTQZD9mjWl2EQJ8=&u=/foo/boo/kb

Thanks.

score 10 · Accepted Answer · answered Apr 15 '11 at 13:08

10

it is pretty simple. I use System.Uri class to parse the url, then remove the q query string parameter, and then build a new url without this parameter:

var url = new Uri("http://abc.com/qwe.aspx?q=DIEYeGJgNwvPSJ32ic1sY5x1ZYjOZTQZD9mjWl2EQJ8=&u=/foo/boo/kb");
var query = HttpUtility.ParseQueryString(url.Query);
query.Remove("q");
UriBuilder ub = new UriBuilder(url);
ub.Query = query.ToString();
var result = ub.Uri.ToString();

Now result holds value: http://abc.com/qwe.aspx?u=/foo/boo/kb.

answered Apr 15 '11 at 13:08

Oleks

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This sould be the safest way to remove the query parameter. – Zebi Apr 15 '11 at 13:15
Too much code to do a simple thing. If the point is that url is the one found in HttpRequest, then, this could be an overkill. I'll vote for regex solution. – Matías Fidemraizer Apr 15 '11 at 13:18
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The regex solution mentioned below as it is written at the moment does not just match the parameter named **q** but instead all parameters that end with **q** and thus won't work as intended. – Marius Schulz Apr 15 '11 at 13:22
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Not the simplest solution, but given the lack of context for the source of the URL, it is definitely the most correct. +1 – Harry Steinhilber Apr 15 '11 at 13:30

score 1 · Answer 2 · answered Apr 15 '11 at 13:07

1

input = Regex.Replace(input, "q=[^&]+", "") would be one way to do it.

answered Apr 15 '11 at 13:07

John M Gant

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You need to be a little careful with this one since a parameter like "uq=something" will be removed unintentionally. – Marius Schulz Apr 15 '11 at 13:10
No it won't, "q=" won't match "qu=". – Antoine Apr 15 '11 at 13:12
@Marius, wouldn't the `q=` part of the regex prevent that? – John M Gant Apr 15 '11 at 13:12
Sorry, I misspelled the parameter name (I've fixed it now). I thought of a parameter called **uq**. – Marius Schulz Apr 15 '11 at 13:13
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@Marius, good point. If that was a possibility, we could always add a look-behind for `[?&]`. – John M Gant Apr 15 '11 at 13:15
@Zebi: Indeed, the pattern matches *q=/foo/boo/* — however, *uq=/foo/boo/* is not supposed to match! – Marius Schulz Apr 15 '11 at 13:21

score 0 · Answer 3 · answered Apr 15 '11 at 13:08

0

Are the positions fixed? You can do one IndexOf("q=") and IndexOf("u=") and use SubString twice to remove the part. An other way would be to use regular expressions.

answered Apr 15 '11 at 13:08

Zebi

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score 0 · Answer 4 · answered Apr 15 '11 at 13:15

Maybe this URL comes from some request, meaning you've that query string in the HttpRequest instance, associated to HttpContext.

In this case, you can always remove "q" query string parameter just by calling HttpContext.Current.Request.QueryString.Remove("q");

Another solution would be the one suggested by Alex.

score -1 · Answer 5 · answered Apr 15 '11 at 13:07

-1

if Q is a fixed parameter....

str = str.Replace("q=DIEYeGJgNwvPSJ32ic1sY5x1ZYjOZTQZD9mjWl2EQJ8=", "");

Otherwise I would do:

var qa = Request.QueryString;
qa.Remove("q");
var queryString = qa.ToString();

answered Apr 15 '11 at 13:07

tster

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This is not helpful — the parameter *name* is fixed, not its value! – Marius Schulz Apr 15 '11 at 13:08
He said it's fixed. Anyways, I added what I would do for a variable value query string. – tster Apr 15 '11 at 13:10
The parameter name is fixed, not the string after **q=**! – Marius Schulz Apr 15 '11 at 13:11
@Marius Schulz, How do you know that? He said `q= is fixed parameter` which makes me think that the parameter doesn't change. – tster Apr 15 '11 at 13:12
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I inferred that just the part **q=** is fixed because Ricky wrote that part in bold. – Marius Schulz Apr 15 '11 at 13:17

A string replacement question with C#

5 Answers5