Regex replace everything except a particular pattern

Question

I\'m looking to extract:

50%

From a string that will have more or less this format:

The 50% is in here somewhere.

I\'d

Answer 1

You can use Regex.Matches and concatenate each matches result. Just pick one you like the most.

//Sadly, we can't extend the Regex class
public class RegExp
{
    //usage : RegExp.Filter("50% of 50% is 25%", @"[0-9]+\%")
    public static string Filter(string input, string pattern)
    {
        return Regex.Matches(input, pattern).Cast()
            .Aggregate(string.Empty, (a,m) => a += m.Value);
    }
}

public static class StringExtension
{
    //usage : "50% of 50% is 25%".Filter(@"[0-9]+\%")
    public static string Filter(this string input, string pattern)
    {
        return Regex.Matches(input, pattern).Cast()
            .Aggregate(string.Empty, (a,m) => a += m.Value);
    }
}