I'm not a big regular expressions expert but this sounds like a
perfect job for it.

Type in ".net regex" in google for some basic samples.  regexlib.com
might have the expression you are looking for.

Hello deepak,

As Robbe already pointed out Regex is the way to go here. Combine it with
a MatchEvaluator and you're all done. Currently I do not have time to work
out an example for you, but I'll probably get round to it somewhere tonight.

Jesse

--
Jesse Houwing
jesse.houwing at sogeti.nl

Hello deepak,

The following code does the trick:

======

private static readonly Regex rx = new Regex("[0-9]{1,2}/[0-9]{1,2}/[0-9]{4}
[0-9]{1,2}:[0-9]{2}:[0-9]{2} (AM|PM)", RegexOptions.IgnoreCase | RegexOptions.Compiled);
private static string ReplaceDates(Match m)
{
   DateTime date = DateTime.ParseExact(m.Value, "M/d/yyyy h:mm:ss tt", CultureInfo.InvariantCulture);
   return date.ToString("s") + "Z";
}

string input = "The description of the problem ERIndia_Bharti / 12/19/2008
8:37:00 PM last comment only ER_Kista / 2/19/2008 9:45:00 AM last comment
only ER_Kista / 2/19/2008 10:45:59 AM last comment only ER_Kista / 2/19/2008
9:47:00 AM";
string output = rx.Replace(input, new MatchEvaluator(ReplaceDates));

======

The regex takes care of finding all occurances of a date/time string in your
original input text.

The MatchEvaluator is used to parse the dates (I used the exact format used
here to make sure it parses correctly).

Then I rewrote every match using the "s" for sortable datetime format. This
doesn't append the "Z" at the end (the u(niversal) format does that, but
that doesn't have the T in the middle). I appended that manually.

I think it solves both your issues, as the format is the same in both strings.
Am I correct?

If you still have any questions, please let me know.

--
Jesse Houwing
jesse.houwing at sogeti.nl