C# Regex.Replace

Question

this is my Set of string inside richtextbox1..

/Category/5
/Category/4
/Category/19
/Category/22
/Category/26
/Category/27
/Category/24
/Category/3
/Category/1
/Category/15
http://example.org/Category/15/noneedtoadd

i want to change all the starting "/" with some url like "http://example.com/"

output:

http://example.com/Category/5
http://example.com/Category/4
http://example.com/Category/19
http://example.com/Category/22
http://example.com/Category/26
http://example.com/Category/27
http://example.com/Category/24
http://example.com/Category/3
http://example.com/Category/1
http://example.com/Category/15
http://example.org/Category/15/noneedtoadd

just asking, what is the pattern for that? :)

Why use an impact wrench when you need a screwdriver?

Michael Todd
– Michael Todd

2011-08-02 18:20:02 +00:00
Commented Aug 2, 2011 at 18:20 — Michael Todd
– Michael Todd, Commented Aug 2, 2011 at 18:20

jdphenix · Accepted Answer · 2014-03-20 05:51:07Z

7

You don't need a regular expression here. Iterate through the items in your list and use String.Format to build the desired URL.

String.Format(@"http://example.com{0}", str);

If you want to check to see whether one of the items in that textbox is a fully-formed URL before prepending the string, then use String.StartsWith (doc).

if (!String.StartsWith("http://")) { 
    // use String.Format 
}

edited Mar 20, 2014 at 5:51

jdphenix

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answered Aug 2, 2011 at 18:16

csano

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2 Comments

Vincent Dagpin Over a year ago

what if inside the richtextbox, there's a string that does not start with / ?

csano Over a year ago

So it's either /category/1 or category/1?

dtb · Accepted Answer · 2014-03-20 14:01:02Z

4

Since you're dealing with URIs, you can take advantage of the Uri Class which can resolve relative URIs:

Uri baseUri = new Uri("http://example.com/");

Uri result1 = new Uri(baseUri, "/Category/5");
// result1 == {http://example.com/Category/5}

Uri result2 = new Uri(baseUri, "http://example.org/Category/15/noneedtoadd");
// result2 == {http://example.org/Category/15/noneedtoadd}

edited Mar 20, 2014 at 14:01

answered Aug 2, 2011 at 18:22

dtb

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Comments

jdphenix · Accepted Answer · 2014-03-20 05:51:22Z

3

The raw regex pattern is ^/ which means that it will match a slash at the beginning of the line.

Regex.Replace (text, @"^/", "http://example.com/")

edited Mar 20, 2014 at 5:51

jdphenix

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answered Aug 2, 2011 at 18:23

agent-j

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2 Comments

Vincent Dagpin Over a year ago

how about if i added multiline "?m"

agent-j Over a year ago

I don't understand what you mean by "?m". Do you mean RegexOptions.MultiLine? If so, that doesn't matter for my regex.

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