Creates a single source file version of DotNetZip

DotNetZipOneFile.cs

using System;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;

namespace ZipReducedOneFile
{
    class Program
    {
        static void Main()
        {
            var files = Directory.EnumerateFiles(@"C:\Temp\DotNetZip\src\Zip", "*.cs")
                .Concat(Directory.EnumerateFiles(@"C:\Temp\DotNetZip\src\BZip2", "*.cs"))
                .Concat(Directory.EnumerateFiles(@"C:\Temp\DotNetZip\src\Zlib", "*.cs"))
                .Concat(Directory.EnumerateFiles(@"C:\Temp\DotNetZip\src\CommonSrc", "CRC32.cs"));

            var lines = from file in files
                        from line in File.ReadAllLines(file)
                        select line;

            var usingRegex = new Regex(@"^using (.+?);");

            var usings = (from line in lines
                          let match = usingRegex.Match(line)
                          let ns = string.Join("", match.Groups[1].Value.Where(ch => !char.IsWhiteSpace(ch)))
                          where match.Success
                          select new { line, ns })
                          // distinct-by ns
                         .GroupBy(x => x.ns).Select(x => x.First().line);

            var remainder = (from line in lines
                             where !usingRegex.IsMatch(line)
                             select line);

            File.WriteAllLines(
                @"C:\Temp\DotNetZip\src\ZipReducedOneFile\DotNetZip.cs", 
                usings.Concat(remainder));
        }
    }
}