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Regular expressions redirection

I want to set redirection from
www.somesite.com/products/dynamicstring/randomtext1/randomtext2
to www.somesite.com/products/dynamicstring
Is it possible to do that through Regex ?
It means if my incming url is
www.somesite.com/products/myproducts/test1/test2 it should redirect to www.somesite.com/products/myproducts/
just briefing more about this :
#TomLord i am using HttpContext.Current.Response.RedirectPermanent(matchingDefinition.To) i have all the redirects "From" and "To" in a class object, in the form of REGEX expressions.Example in From "/product/*" and To "/products" , i am reading these object and trying to redirect them, but i am not able to redirect something like /products/dynamicstring/randomtext1/ to /products/dynamicstring where dynamic string is random string , i dont find any regular expression which can be use to do this. For example /products/samples/randomtext1 should redirect to /products/samples/

Redirection cannot be done with regex alone. Google a bit what is a regular expression in reality. The short answer is: it's string-like expression that describes search pattern. So it can't redirect, not even replace a substring with substring or do anything else then match and capture parts of the matched string.
That being said, regex can help us do what you wanna. I am gonna assume you can use Javascript, cause I can't put a solution in every language. I am also gonna assume you will try to go over the code not copy paste and press enter. If you only need that hire a programmer. If you use another language, principle should be the same:
obtain URL
define regex
use capture group to extract the part of your URL that you need
construct a new URL
redirect to it
While matching the URLs in general is a fair bit more complex, like:
^(?:https?://)?(?:[\w]+\.)(?:\.?[\w]{2,})+$
As long as you are sure you will only be getting URLs and in the format you wanna, we will do it far simpler.
Basically, let's say you have:
some text with 2 dots that ends in com
then a /products/dynamicstring/
then text
then /
then text
As a regex that is:
/\w*.\w*.com\/products\/dynamicstring\/\w*\/\w*/g
Curde matching is done, but we still need to add a capture group we will use to extract part of the string we need:
/(\w*.\w*.com\/products\/)dynamicstring\/\w*\/\w*/g
Oke, now let's leverage this regex to do rest of the work:
Define regex:
var regex = /\w*.\w*.com\/products\/dynamicstring\/\w*\/\w*/g;
Get current URL. If you already have URL use it.
var currUrl = window.location.href;
Extract capture group from string:
var match = regex.exec(currUrl);
Use that to get a new URL from old one:
var redirectUrl = match[1] + myproducts/
Finally, we redirect with:
window.location.replace(redirectUrl);
I wrote all this straight from my head so I recommend you go over each step, look how it works, read some documentation about functions used. You might find an error as well as learn a lot.

Extracts all sub strings between string separators in a string (C#)

I'm trying to parse content of a string to see if the string includes urls, to convert the full string to html, to make the string clickable.
I'm not sure if there is a smarter way of doing this, but I started trying creating a parser with the Split method for strings, or Regex.Split in C#. But I can't find a good way of doing it.
(It is a ASP.NET MVC application, so perhaps there is some smarter way of doing this)
I want to ex. convert the string;
"Customer office is responsible for this. Contact info can be found {link}{www.customerservice.com}{here!}{link} More info can be found {link}{www.customerservice.com/moreinfo}{here!}{link}"
Into
"Customer office is responsible for this. Contact info can be found <a href=www.customerservice.com>here!</a> More info can be found <a href=www.customerservice.com/moreinfo>here!</a>"
i.e.
{link}{url}{text}{link} --> <a href=url>text</a>
Anyone have a good suggestion? I can also change the way the input string is formatted.

You can use the following to match:
{link}{([^}]*)}{([^}]*)}{link}
And replace with:
<a href=$1>$2</a>
See DEMO
Explanation:
{link} match {link} literally
{([^}]*)} match all characters except } in capturing group 1 (for url)
{([^}]*)} match all characters except } in capturing group 2 (for value)
{link} match {link} literally again

you can use regex as
{link}{(.*?)}{(.*?)}{link}
and substution as
<a href=\1>\2</a>
Regex

For your simple link format {link}{url}{text} you can use simple Regex.Replace:
Regex.Replace(input, #"\{link\}\{([^}]*)\}\{([^}]*)\}", #"$2");

Also this non-regex idea may help
var input = "Customer office is responsible for this. Contact info can be found {link}{www.customerservice.com}{here!}{link} More info can be found {link}{www.customerservice.com/moreinfo}{here!}{link}";
var output = input.Replace("{link}{", "<a href=")
.Replace("}{link}", "</a>")
.Replace("}{", ">");

How to remove the domain name?

I have one sharepoint application, in this i have to show the current user, i used SPContext.Current.Web.CurrentUser.LoginName. then it returns XXXXXX\abida. But i want only the username like abida. How to achieve this requirement?

Note that we have to escape the slash...
string loginName = SPContext.Current.Web.CurrentUser.LoginName;
string[] loginNameParts = loginName.Split('\\');
string loginNameWithoutDomain = nameParts[1];
I presume you are doing this in order to use the name-only for some reason and that you aren't relying on the user name being unique in its own right. You could have DOMAIN1\BobSmith and DOMAIN2\BobSmith - so if you were using "BobSmith" as a unique user name, you could come unstuck.

you do not. The name is not guaranteed to be unique without the domain prefix. If you erally want to show it without, then just remove it - split the string at the "\" and use the second element. There are multiple ways do do that, from the Split method on the string to using IndexOf for the "\" and then substring to extract the reminder.

Regular expression to define format of backup filenames

In the application I am currently working on, I have an option to create automatic backups of a certain file on the hard disk. What I would like to do is offer the user the possibility to configure the name of the file and its extension.
For example, the backup filename could be something like : "backup_month_year_username.bak". I had the idea to save the format in the form of a regular expression. For the example above, the regexp would look like :
"^backup_(?<Month>\d{2})_(?<Year>\d{2})_(?<Username>\w).(?<extension>bak)$"
I thought about using regex because I will also have to browse through the directory of backuped files to delete those older than a certain date. The main trouble I have now is how to create a filename using the regex. In a way I should replace the tags with the information. I could do that using regex.replace and another regex, but I feel it's a big weird doing that and it might be a better way.
Thanks
[Edit] Maybe I wasn't really clear in the first go, but the idea is of course that the user (in this case an admin that will know regex syntax) will have the possibility to modify the form of the filename, that's all the idea behind it[/Edit]

... and if the regex changes, it is next to impossible to reconstruct a string from a given regex.
Edit:
Create some predefined "place-holders": %u could be the user's name, %y could be the year, etc.:
backup_%m_%y_%u.bak
and then simple replace the %? with their actual values.

It sounds like you're trying to use the regular expression to create the file name from a pattern which the user should be able to specify.
Regular expressions can - AFAIK - not be used to create output, but only to validate input, so you'd have the user specify two things:
a file name production pattern like Bart suggested
a validation pattern in form of a regular expression that helps you split the file names into their parts
EDIT
By the way, your sample regex contains an error: The "." is use for "any character", also \w only matches one word character, so I guess you meant to write
"^backup_(?<Month>\d{2})_(?<Year>\d{2})_(?<Username>\w+)\.(?<extension>bak)$"

If the filename is always in this form, there is no reason for a regex, as it's easier to process with string.Split ...

With Bart's solution it is easy enough to split (using string.Split) the generated file name using underscore as the delimiter, to get back the information.

Ok, I think I have found a way to use only the regex. As I am using groups to get the information, I will use another regular expression to match the regular expression and replace the groups with the value:
Regex rgx = new Regex("\(\?\<Month\>.+?\)");
rgx.Replace("^backup_(?<Month>\d{2})_(?<Year>\d{2})_(?<Username>\w+)\.(?<extension>bak)$"
, DateTime.Now.Month.ToString());
Ok, it's really a hack, but at least it works and I have only one pattern defined by the user. It might not work if the regex is too complex, but I think I can deal with that problem.
What do you think?

C# Need to locate web addresses using REGEX is that possible?

C# Need to locate web addresses using REGEX is that possible?
Basically I need to parse a string prior to loading it into a WebBrowser
myString = "this is an example string http://www.google.com , and I need to make the link clickable";
webBrow.DocumentText = myString;
Basically what I want to happen is a replace of the web address so that it looks like a hyperlink, and do this with any address pulled in to the string. I would need to replace the web address so that web address would read like
<a href='web address'>web address</a>
This would allow me to have the links clickable..
Any Ideas?

new Regex(#"https?://([-\w\.]+)+(:\d+)?(/([\w/_\.]*(\?\S+)?)?)?").Match(myString)

It's possible depending on how strict or permissive you want your parsing to be.
As a first cut, you can try #"\bhttp://\S+" which will match any string starting with "http://" at a word boundary (non-word character, such as whitespace or punctuation).
To search using a regex and replace all occurrences with your custom text, you could use the Regex.Replace method.
You may want to read up on Regular Expression Language Elements to learn more.