c# find and replace urls from string with regex

Question

i want to replace url for example www.google.com or http://www.google.com with www.google.com i have a code for this

str = Regex.Replace(str,
                @"((http|ftp|https):\/\/[\w\-_]+(\.[\w\-_]+)+([\w\-\.,@?^=%&:/~\+#]*[\w\-\@?^=%&/~\+#])?)",
                "<a target='_blank' href='$1'>$1</a>");

it is working with http://www.google.com but it is not working with www.google.com or subdomain.google.com which regex code matches with every url links. and when i wrote a long link it will write same of the url for example

http://www.google.com/search/asdadad/sdsdsd/sadasdx-sadasd-weqeqwe-zxcxzc.com

. i want to write it as

<a href="http://www.google.com/search/asdadad/sdsdsd/sadasdx-sadasd-weqeqwe-zxcxzc.com">google.com/asdas... </a>

what is the best way to make this? i am new for regex

Answer 1

This will also catch www.test.com:

(((http|ftp|https):\/\/)?[\w\-_]+(\.[\w\-_]+)+([\w\-\.,@?^=%&:\/~\+#]*[\w\-\@?^=%&\/~\+#])?)
 ↑---------------------↑↑

Just surround the part thats optional and append a questionmark. You can check it out here.

---

The first match in this regex (matches are defined with "(" and ")") is the whole url. So you could use replacing like this:

Regex rgxUrls = new Regex(pattern);
string result = rgxUrls.Replace(yourText, "<a href=\"$1\"> space for custom text </a>");
                                                      ↑ Inserts first match

Where I've used $1 you can also use $2 - $5. Check the image above thats showing which groups are capturing which part of the url.

Full test can be found here.
Just click execute on the top.

Output:

---

According the comments, how group caption works:

Text: "this is your text to search"  
Pattern: "text to"

Match[0] will always match your whole match text to. Every groups above like Match[1] or Match[2] has to be defined with "(" and ")".

Text: "this is your text to search"  
Pattern: "text (to)"  
Match[0]: "text to"  
Match[1]: "to"  


Pattern: "text (t(o))"  
Match[0]: "text to"  
Match[1]: "to"  
Match[2]: "o"  

The caption with "()" works from the outside to the inside.

$1
(((http|ftp|https):\/\/)?[\w\-_]+(\.[\w\-_]+)+([\w\-\.,@?^=%&:\/~\+#]*[\w\-\@?^=%&\/~\+#])?)
↑--------------------------------------------------------------------------------------------------↑

$2 (http://)
(((http|ftp|https):\/\/)?[\w\-_]+(\.[\w\-_]+)+([\w\-\.,@?^=%&:\/~\+#]*[\w\-\@?^=%&\/~\+#])?)
 ↑---------------------↑

$3 (http)
(((http|ftp|https):\/\/)?[\w\-_]+(\.[\w\-_]+)+([\w\-\.,@?^=%&:\/~\+#]*[\w\-\@?^=%&\/~\+#])?)
  ↑--------------↑

$4 (.com)
(((http|ftp|https):\/\/)?[\w\-_]+(\.[\w\-_]+)+([\w\-\.,@?^=%&:\/~\+#]*[\w\-\@?^=%&\/~\+#])?)
                                 ↑----------↑   

$5 (/appendedSubdirectory/anotherOne)
(((http|ftp|https):\/\/)?[\w\-_]+(\.[\w\-_]+)+([\w\-\.,@?^=%&:\/~\+#]*[\w\-\@?^=%&\/~\+#])?)
                                              ↑--------------------------------------------------↑   

I cant explain everything about regex in here. This question looks solved for me. If you've got deeper questions according regex start a new one and show some effort you've done before.