Split a flat file maintaining header

SplitFlatFile.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace SplitFlatFile {
	class Program {
		static void Main(string[] args) {
			try {
				string inputFile = args[0];
				int linesPerFile;

				var fileInfo = new FileInfo(inputFile);
				if (!fileInfo.Exists)
					throw new Exception("File does not exist");
				double linesDbl = double.Parse(args[1]);
				linesPerFile = (int)linesDbl;
				if (linesPerFile != linesDbl)
					throw new Exception("Specify a valid number of lines");

				int count = 1;
				var lines = File.ReadLines(inputFile).Skip(1).ToList();
				var header = File.ReadLines(inputFile).Take(1);

				var log = new List<string>();
				log.Add(string.Format("Source,{0}", lines.Count()));

				foreach (var chunk in Chunk(lines, linesPerFile)) {
					var filename = Path.Combine(fileInfo.Directory.FullName, string.Format("{0}_{1:D2}{2}", Path.GetFileNameWithoutExtension(fileInfo.Name), count, fileInfo.Extension));
					File.WriteAllLines(filename, header);
					File.AppendAllLines(filename, chunk);

					log.Add(string.Format("{0},{1}", filename, File.ReadAllLines(filename).Count()));
					count++;
				}

				File.WriteAllLines(Path.Combine(fileInfo.Directory.FullName, string.Format("{0}_log.csv", Path.GetFileNameWithoutExtension(fileInfo.Name))), log);
			} catch (Exception ex) {
				PrintUsage();
				Console.WriteLine("Error");
				Console.WriteLine(ex.Message);
			}
		}

		private static void PrintUsage() {
			Console.WriteLine("Usage: SplitFlatFile filename N");
		}

		/// <summary>
		/// Break a list of items into chunks of a specific size, perf may be O(n^2) unless you use it on a List or Array
		/// http://stackoverflow.com/questions/419019/split-list-into-sublists-with-linq
		/// </summary>
		public static IEnumerable<IEnumerable<T>> Chunk<T>(IEnumerable<T> source, int chunksize) {
			while (source.Any()) {
				yield return source.Take(chunksize);
				source = source.Skip(chunksize);
			}
		}

	}
}