[C#.NET] 書き込みモードで開かれたファイルを読み取る ReadLines メソッド

using System.Collections.Generic;
using System.IO;
using System.Text;

/// <summary>
/// Provides iterators to read lines in a file.
/// </summary>
public static class TextFile
{
    /// <summary>
    /// Enumrates lines in the file with the file share setting.
    /// </summary>
    /// <param name="path"></param>
    /// <param name="fileShare"></param>
    /// <param name="encoding"></param>
    /// <returns></returns>
    public static IEnumerable<string> ReadLines(
        string path,
        FileShare fileShare = FileShare.ReadWrite,
        Encoding encoding = null)
    {
        using (var stream = new FileStream(path, FileMode.Open, FileAccess.Read, fileShare))
        using (var reader = new StreamReader(stream, encoding ?? Encoding.UTF8))
        {
            string line;
            while ((line = reader.ReadLine()) != null)
            {
                yield return line;
            }
        }
    }
}

var lines = FileText.ReadLines(path)
    .Skip(2) // 2 行スキップ
    .Where(x => x.Contains("HOGE")) // HOGE を含んでいれば
    .Select(x => ConvertLine(x)); // なんか処理
foreach (var line in lines)
{
    Console.WriteLine(line);
}

[ResourceExposure(ResourceScope.Machine)]
[ResourceConsumption(ResourceScope.Machine)]
public static IEnumerable<String> ReadLines(String path)
{
	if (path == null)
		throw new ArgumentNullException("path");
	if (path.Length == 0)
		throw new ArgumentException(Environment.GetResourceString("Argument_EmptyPath"), "path");
	Contract.EndContractBlock();

	return ReadLinesIterator.CreateIterator(path, Encoding.UTF8);
}

internal class ReadLinesIterator : Iterator<string>
{
    // ～中略～
    private static ReadLinesIterator CreateIterator(string path, Encoding encoding, StreamReader reader)
    {
        return new ReadLinesIterator(path, encoding, reader ?? new StreamReader(path, encoding));
    }
}

Stream stream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read, DefaultFileStreamBufferSize, FileOptions.SequentialScan, Path.GetFileName(path), false, false, checkHost);