C#でSharpZipLibでzipファイルを展開するサンプルコード

cd (mkdir SharpZipLibSample01)
dotnet new console -f net8.0
dotnet add package SharpZipLib --version 1.4.2

using System.Diagnostics;
using System.Security.AccessControl;
using ICSharpCode.SharpZipLib.Zip;

// zipEntries は List<string>（エントリ名のリスト）を想定
var stopwatch = Stopwatch.StartNew();

const string OUTPUT_DIR = @"./output";
const string INPUT_ACHIVE_FILE = @"G:\testdata\Archive.zip";
Directory.CreateDirectory(OUTPUT_DIR!);

List<string> zipEntries;
using (var fs = File.OpenRead(INPUT_ACHIVE_FILE))
using (var zip = new ZipFile(fs))
{
    zipEntries = zip.Cast<ZipEntry>()
        .Where(e => !e.IsDirectory)
        .Select(e => e.Name)
        .ToList();
}

using var zipStream = File.OpenRead(INPUT_ACHIVE_FILE);
using var zipFile = new ZipFile(zipStream);

foreach (var entryName in zipEntries)
{
    var entry = zipFile.GetEntry(entryName);
    if (entry == null || entry.IsDirectory) continue;

    using var entryStream = zipFile.GetInputStream(entry);
    var outPath = Path.Combine(OUTPUT_DIR, entry.Name);

    using var outFile = File.Create(outPath);
    entryStream.CopyTo(outFile);
}

stopwatch.Stop();
Console.WriteLine($"直列処理時間: {stopwatch.ElapsedMilliseconds} ms");

using System.Diagnostics;
using System.Security.AccessControl;
using ICSharpCode.SharpZipLib.Zip;

// zipEntries は List<string>（エントリ名のリスト）を想定
var stopwatch = Stopwatch.StartNew();

const string OUTPUT_DIR = @"./output";
const string INPUT_ACHIVE_FILE = @"G:\testdata\Archive.zip";
Directory.CreateDirectory(OUTPUT_DIR!);

List<string> zipEntries;
using (var fs = File.OpenRead(INPUT_ACHIVE_FILE))
using (var zip = new ZipFile(fs))
{
    zipEntries = zip.Cast<ZipEntry>()
        .Where(e => !e.IsDirectory)
        .Select(e => e.Name)
        .ToList();
}

using var zipStream = File.OpenRead(INPUT_ACHIVE_FILE);
using var zipFile = new ZipFile(zipStream);

var options = new ParallelOptions
{
    MaxDegreeOfParallelism = Environment.ProcessorCount / 1
};

// zipEntries は List<string>
Parallel.ForEach(zipEntries, options, entryName =>
{
    using var zipStream = File.OpenRead(INPUT_ACHIVE_FILE);           // 各スレッドで独立に開く
    using var zipFile = new ZipFile(zipStream);
    var entry = zipFile.GetEntry(entryName);
    if (entry == null || entry.IsDirectory) return;

    using var entryStream = zipFile.GetInputStream(entry);
    var outPath = Path.Combine("output", entry.Name);

    using var outFile = File.Create(outPath);
    entryStream.CopyTo(outFile);
});


stopwatch.Stop();
Console.WriteLine($"並列処理時間（MaxThreads={options.MaxDegreeOfParallelism}）: {stopwatch.ElapsedMilliseconds} ms");