Regex vs. where clause

Benchmark.csx

using System.Diagnostics;
using System.Text.RegularExpressions;

var iterations = 1000;
var badString = "http://this.is.my/INVALID#!@STRING";
var replaceRegex = new Regex("[^a-z0-9]", RegexOptions.Compiled | RegexOptions.IgnoreCase);

// Test query
var sw = Stopwatch.StartNew();

for(int i=0; i<iterations; i++)
{
    var newString = string.Join(string.Empty, badString.Where(char.IsLetterOrDigit));
    if(i == 0)
        Console.WriteLine(newString);
}

sw.Stop();
Console.WriteLine(sw.ElapsedTicks);

// Test regex
sw = Stopwatch.StartNew();

for(int i=0; i<iterations; i++)
{
    var newString = replaceRegex.Replace(badString, string.Empty);
    if(i == 0)
        Console.WriteLine(newString);
}
sw.Stop();
Console.WriteLine(sw.ElapsedTicks);

// Test string builder

sw = Stopwatch.StartNew();

for(int i=0; i<iterations; i++)
{
    var sb = new StringBuilder();
    foreach(char c in badString)
    {
        if(char.IsLetterOrDigit(c))
        {
            sb.Append(c);
        }
    }

    var newString = sb.ToString();
    if(i == 0)
        Console.WriteLine(newString);
}

sw.Stop();
Console.WriteLine(sw.ElapsedTicks);