C Sharp Find Hexadecimal Numbers

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This recipe will limit the input to numbers and letters that are valid for hexadecimal representations.

[edit] code

using System;
using System.IO;
using System.Text.RegularExpressions;
public class Recipe
{
    private static Regex _Regex = new Regex( @"^[0-9a-f]+$",
        RegexOptions.IgnoreCase );
    public void Run(string fileName)
    {
        String line;
        int lineNbr = 0;
        using (StreamReader sr = new StreamReader(fileName))
        {
            while(null != (line = sr.ReadLine()))
            {
                lineNbr++;
                if (_Regex.IsMatch(line))
                {
                    Console.WriteLine("Found match '{0}' at line {1}",
                        line,
                        lineNbr);
                }
            }
        }
    }
    public static void Main( string[] args )
    {
        Recipe r = new Recipe();
        r.Run(args[0]);
    }
}

[edit] How It Works

This recipe uses a simple character class to limit the input to digits and the letters a through f:

Regular Expression Description
^ the beginning of the line, followed by . . .
[0-9a-f] a character class that matches the digits zero through nine and the letters
\s a through f . . .
+ found one or more times . . .
$ the end of the line.

Alternatively, you can replace 0-9 in the character class with \d.

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