How to extract the strings between two special characters using Regular Expressions in C#

You can do it like this

using System.Text.RegularExpressions;
using System;

public class Test
{
        public static void Main(){
                string s = "My name is #Dave# and I am #18# years old";
                Regex r = new Regex(@"#(.+?)#");
                MatchCollection mc = r.Matches(s);
                Console.WriteLine("Name is " + mc[0].Groups[1].Value);
                Console.WriteLine("Age is " + mc[1].Groups[1].Value);
        }
}

Demo here

I don't know what your application is but I must say this is not a very robust looking data transfer method. Start getting a few extra #s in there and it all goes wrong. For example people with # in their names!

However if you can guarantee that you will always be working with a string of this format then this does work.

Explanation of Regex #(.+?)#

First # matches a #

( begins a group. Indexed into in .Groups[1] in the code. [0] is the whole match eg #Dave# not just Dave

.+? matches at least one character. . is a character. + is repetition (at least once). And ? tells the regex engine to be lazy - so don't match a # as that will get matched by our final #

) close the group

# matches another # - the 'closing' one in this case

A regular expression such as "#[^#]+#" would match a hash, followed by one or more none-hash characters, followed by another hash.

There are various alternatives that would work for this such as "#.*?#".

The following code would output the #P_NAME# and #P_AGE#.

string p = "My Name is #P_NAME# and \r\n I am #P_AGE# years old";
Regex reg = new Regex("#[^#]+#");

MatchCollection matches = reg.Matches(p);
foreach (Match m in matches)
{
    Console.WriteLine(m.Value);
}

Thanks everyone..

Following worked for me...

string str = "My Name is #P_NAME# and \r\n I am #P_AGE# years old";

MatchCollection allMatchResults = null;
var regexObj = new Regex(@"#\w*#");
allMatchResults = regexObj.Matches(str);

'allMatchResults' contains #P_NAME# and #P_AGE# (i.e. including # character). But having it helps my other logic