C#によるPDFバッチ処理：ドキュメントワークフローを大規模に自動化する

Install-Package IronPdf

dotnet add package IronPdf

using IronPdf;
using System;
using System.IO;
using System.Linq;
using System.Collections.Generic;

string inputFolder = "documents/";
string outputFolder = "merged/";

Directory.CreateDirectory(outputFolder);

// Group PDFs by prefix (e.g., "invoice-2026-01-*.pdf" -> one merged file)
var pdfFiles = Directory.GetFiles(inputFolder, "*.pdf");
var groups = pdfFiles
    .GroupBy(f => Path.GetFileName(f).Split('-').Take(3).Aggregate((a, b) => $"{a}-{b}"))
    .Where(g => g.Count() > 1);

Console.WriteLine($"Found {groups.Count()} groups to merge");

foreach (var group in groups)
{
    string groupName = group.Key;
    var filesToMerge = group.OrderBy(f => f).ToList();

    Console.WriteLine($"Merging {filesToMerge.Count} files into {groupName}.pdf");

    try
    {
        // Load all PDFs for this group
        var pdfDocs = new List<PdfDocument>();
        foreach (string filePath in filesToMerge)
        {
            pdfDocs.Add(PdfDocument.FromFile(filePath));
        }

        // Merge all documents
        using var merged = PdfDocument.Merge(pdfDocs);
        merged.SaveAs(Path.Combine(outputFolder, $"{groupName}-merged.pdf"));

        // Dispose source documents
        foreach (var doc in pdfDocs)
        {
            doc.Dispose();
        }

        Console.WriteLine($"  [OK] Created {groupName}-merged.pdf ({merged.PageCount} pages)");
    }
    catch (Exception ex)
    {
        Console.WriteLine($"  [ERROR] {groupName}: {ex.Message}");
    }
}

Console.WriteLine("\nMerge complete");

using IronPdf;
using System;
using System.IO;
using System.Threading.Tasks;
using System.Threading;

string inputFolder = "originals/";
string outputFolder = "compressed/";

Directory.CreateDirectory(outputFolder);

string[] pdfFiles = Directory.GetFiles(inputFolder, "*.pdf");
Console.WriteLine($"Found {pdfFiles.Length} PDFs to compress");

long totalOriginalSize = 0;
long totalCompressedSize = 0;
int processed = 0;

var options = new ParallelOptions
{
    MaxDegreeOfParallelism = Environment.ProcessorCount / 2
};

Parallel.ForEach(pdfFiles, options, pdfFile =>
{
    string fileName = Path.GetFileName(pdfFile);
    string outputPath = Path.Combine(outputFolder, fileName);

    try
    {
        long originalSize = new FileInfo(pdfFile).Length;
        Interlocked.Add(ref totalOriginalSize, originalSize);

        using var pdf = PdfDocument.FromFile(pdfFile);

        // Apply compression with JPEG quality setting (0-100, lower = more compression)
        pdf.CompressAndSaveAs(outputPath, 60);

        long compressedSize = new FileInfo(outputPath).Length;
        Interlocked.Add(ref totalCompressedSize, compressedSize);
        Interlocked.Increment(ref processed);

        double reduction = (1 - (double)compressedSize / originalSize) * 100;
        Console.WriteLine($"[OK] {fileName}: {originalSize / 1024}KB → {compressedSize / 1024}KB ({reduction:F1}% reduction)");
    }
    catch (Exception ex)
    {
        Console.WriteLine($"[ERROR] {fileName}: {ex.Message}");
    }
});

double totalReduction = (1 - (double)totalCompressedSize / totalOriginalSize) * 100;
Console.WriteLine($"\nCompression complete:");
Console.WriteLine($"  Files processed: {processed}");
Console.WriteLine($"  Total original: {totalOriginalSize / 1024 / 1024}MB");
Console.WriteLine($"  Total compressed: {totalCompressedSize / 1024 / 1024}MB");
Console.WriteLine($"  Overall reduction: {totalReduction:F1}%");

using IronPdf;
using System;
using System.IO;
using System.Threading.Tasks;
using System.Threading;
using System.Collections.Concurrent;

string inputFolder = "input/";
string outputFolder = "output/";
string errorLogPath = "error-log.txt";

Directory.CreateDirectory(outputFolder);

string[] htmlFiles = Directory.GetFiles(inputFolder, "*.html");
var renderer = new ChromePdfRenderer();
var errorLog = new ConcurrentBag<string>();

int processed = 0;
int failed = 0;
int retried = 0;

const int maxRetries = 3;

var options = new ParallelOptions
{
    MaxDegreeOfParallelism = Environment.ProcessorCount / 2
};

Parallel.ForEach(htmlFiles, options, htmlFile =>
{
    string fileName = Path.GetFileNameWithoutExtension(htmlFile);
    string outputPath = Path.Combine(outputFolder, $"{fileName}.pdf");
    int attempt = 0;
    bool success = false;

    while (attempt < maxRetries && !success)
    {
        attempt++;
        try
        {
            using var pdf = renderer.RenderHtmlFileAsPdf(htmlFile);
            pdf.SaveAs(outputPath);
            success = true;
            Interlocked.Increment(ref processed);

            if (attempt > 1)
            {
                Interlocked.Increment(ref retried);
                Console.WriteLine($"[OK] {fileName}.pdf (succeeded on attempt {attempt})");
            }
            else
            {
                Console.WriteLine($"[OK] {fileName}.pdf");
            }
        }
        catch (Exception ex) when (IsTransientException(ex) && attempt < maxRetries)
        {
            // Transient error - wait and retry with exponential backoff
            int delayMs = (int)Math.Pow(2, attempt) * 500;
            Console.WriteLine($"[RETRY] {fileName}: {ex.Message} (attempt {attempt}, waiting {delayMs}ms)");
            Thread.Sleep(delayMs);
        }
        catch (Exception ex)
        {
            // Non-transient error or max retries exceeded
            Interlocked.Increment(ref failed);
            string errorMessage = $"{DateTime.Now:yyyy-MM-dd HH:mm:ss} | {fileName} | {ex.GetType().Name} | {ex.Message}";
            errorLog.Add(errorMessage);
            Console.WriteLine($"[ERROR] {fileName}: {ex.Message}");
        }
    }
});

// Write error log
if (errorLog.Count > 0)
{
    File.WriteAllLines(errorLogPath, errorLog);
}

Console.WriteLine($"\nBatch complete:");
Console.WriteLine($"  Processed: {processed}");
Console.WriteLine($"  Failed: {failed}");
Console.WriteLine($"  Retried: {retried}");
if (failed > 0)
{
    Console.WriteLine($"  Error log: {errorLogPath}");
}

// Helper to identify transient exceptions worth retrying
bool IsTransientException(Exception ex)
{
    return ex is IOException ||
           ex is OutOfMemoryException ||
           ex.Message.Contains("timeout", StringComparison.OrdinalIgnoreCase) ||
           ex.Message.Contains("locked", StringComparison.OrdinalIgnoreCase);
}

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

string inputFolder = "input/";
string outputFolder = "output/";
string checkpointPath = "checkpoint.txt";
string errorLogPath = "errors.txt";

Directory.CreateDirectory(outputFolder);

// Load checkpoint - files already processed successfully
var completedFiles = new HashSet<string>();
if (File.Exists(checkpointPath))
{
    completedFiles = new HashSet<string>(File.ReadAllLines(checkpointPath));
    Console.WriteLine($"Resuming from checkpoint: {completedFiles.Count} files already processed");
}

// Get files to process (excluding already completed)
string[] allFiles = Directory.GetFiles(inputFolder, "*.html");
string[] filesToProcess = allFiles
    .Where(f => !completedFiles.Contains(Path.GetFileName(f)))
    .ToArray();

Console.WriteLine($"Files to process: {filesToProcess.Length} (skipping {completedFiles.Count} already done)");

var renderer = new ChromePdfRenderer();
var checkpointLock = new object();
int processed = 0;
int failed = 0;

var options = new ParallelOptions
{
    MaxDegreeOfParallelism = Environment.ProcessorCount / 2
};

Parallel.ForEach(filesToProcess, options, htmlFile =>
{
    string fileName = Path.GetFileName(htmlFile);
    string baseName = Path.GetFileNameWithoutExtension(htmlFile);
    string outputPath = Path.Combine(outputFolder, $"{baseName}.pdf");

    try
    {
        using var pdf = renderer.RenderHtmlFileAsPdf(htmlFile);
        pdf.SaveAs(outputPath);

        // Record success in checkpoint (thread-safe)
        lock (checkpointLock)
        {
            File.AppendAllText(checkpointPath, fileName + Environment.NewLine);
        }

        Interlocked.Increment(ref processed);
        Console.WriteLine($"[OK] {baseName}.pdf");
    }
    catch (Exception ex)
    {
        Interlocked.Increment(ref failed);

        // Log error for review
        lock (checkpointLock)
        {
            File.AppendAllText(errorLogPath,
                $"{DateTime.Now:yyyy-MM-dd HH:mm:ss} | {fileName} | {ex.Message}{Environment.NewLine}");
        }

        Console.WriteLine($"[ERROR] {fileName}: {ex.Message}");
    }
});

Console.WriteLine($"\nBatch complete:");
Console.WriteLine($"  Newly processed: {processed}");
Console.WriteLine($"  Failed: {failed}");
Console.WriteLine($"  Total completed: {completedFiles.Count + processed}");
Console.WriteLine($"  Checkpoint saved to: {checkpointPath}");

using IronPdf;
using System;
using System.IO;
using System.Threading.Tasks;
using System.Threading;
using System.Diagnostics;

string inputFolder = "input/";
string outputFolder = "output/";

Directory.CreateDirectory(outputFolder);

string[] htmlFiles = Directory.GetFiles(inputFolder, "*.html");
var renderer = new ChromePdfRenderer();

Console.WriteLine($"Processing {htmlFiles.Length} files with {Environment.ProcessorCount} CPU cores");

int processed = 0;
var stopwatch = Stopwatch.StartNew();

// Configure parallelism based on system resources
// Rule of thumb: ProcessorCount / 2 for memory-intensive operations
var options = new ParallelOptions
{
    MaxDegreeOfParallelism = Math.Max(1, Environment.ProcessorCount / 2)
};

Console.WriteLine($"Max parallelism: {options.MaxDegreeOfParallelism}");

// Use Parallel.ForEach for CPU-bound batch operations
Parallel.ForEach(htmlFiles, options, htmlFile =>
{
    string fileName = Path.GetFileNameWithoutExtension(htmlFile);
    string outputPath = Path.Combine(outputFolder, $"{fileName}.pdf");

    try
    {
        // Render HTML to PDF
        using var pdf = renderer.RenderHtmlFileAsPdf(htmlFile);
        pdf.SaveAs(outputPath);

        int current = Interlocked.Increment(ref processed);

        // Progress reporting every 10 files
        if (current % 10 == 0)
        {
            double elapsed = stopwatch.Elapsed.TotalSeconds;
            double rate = current / elapsed;
            double remaining = (htmlFiles.Length - current) / rate;
            Console.WriteLine($"Progress: {current}/{htmlFiles.Length} ({rate:F1} files/sec, ~{remaining:F0}s remaining)");
        }
    }
    catch (Exception ex)
    {
        Console.WriteLine($"[ERROR] {fileName}: {ex.Message}");
    }
});

stopwatch.Stop();
double totalRate = processed / stopwatch.Elapsed.TotalSeconds;

Console.WriteLine($"\nComplete:");
Console.WriteLine($"  Files processed: {processed}/{htmlFiles.Length}");
Console.WriteLine($"  Total time: {stopwatch.Elapsed.TotalSeconds:F1}s");
Console.WriteLine($"  Average rate: {totalRate:F1} files/sec");
Console.WriteLine($"  Time per file: {stopwatch.Elapsed.TotalMilliseconds / processed:F0}ms");

// Memory monitoring helper (call between chunks for large batches)
void CheckMemoryPressure()
{
    const long memoryThreshold = 4L * 1024 * 1024 * 1024; // 4 GB
    long currentMemory = GC.GetTotalMemory(forceFullCollection: false);

    if (currentMemory > memoryThreshold)
    {
        Console.WriteLine($"Memory pressure detected ({currentMemory / 1024 / 1024}MB), forcing GC...");
        GC.Collect();
        GC.WaitForPendingFinalizers();
        GC.Collect();
    }
}

using IronPdf;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using System.Threading;
using System.Collections.Concurrent;
using System.Diagnostics;
using System.Text.Json;

// Configuration
var config = new PipelineConfig
{
    InputFolder = "input/",
    OutputFolder = "output/",
    ArchiveFolder = "archive/",
    ErrorFolder = "errors/",
    CheckpointPath = "pipeline-checkpoint.json",
    ReportPath = "pipeline-report.json",
    MaxConcurrency = Math.Max(1, Environment.ProcessorCount / 2),
    MaxRetries = 3,
    JpegQuality = 70
};

// Initialize folders
Directory.CreateDirectory(config.OutputFolder);
Directory.CreateDirectory(config.ArchiveFolder);
Directory.CreateDirectory(config.ErrorFolder);

// Load checkpoint for resume capability
var checkpoint = LoadCheckpoint(config.CheckpointPath);
var results = new ConcurrentBag<ProcessingResult>();
var stopwatch = Stopwatch.StartNew();

// Get files to process
string[] allFiles = Directory.GetFiles(config.InputFolder, "*.html");
string[] filesToProcess = allFiles
    .Where(f => !checkpoint.CompletedFiles.Contains(Path.GetFileName(f)))
    .ToArray();

Console.WriteLine($"Pipeline starting:");
Console.WriteLine($"  Total files: {allFiles.Length}");
Console.WriteLine($"  Already processed: {checkpoint.CompletedFiles.Count}");
Console.WriteLine($"  To process: {filesToProcess.Length}");
Console.WriteLine($"  Concurrency: {config.MaxConcurrency}");

var renderer = new ChromePdfRenderer();
var checkpointLock = new object();

var options = new ParallelOptions
{
    MaxDegreeOfParallelism = config.MaxConcurrency
};

Parallel.ForEach(filesToProcess, options, inputFile =>
{
    var result = new ProcessingResult
    {
        FileName = Path.GetFileName(inputFile),
        StartTime = DateTime.UtcNow
    };

    try
    {
        // Stage: Pre-validation
        if (!ValidateInput(inputFile))
        {
            result.Status = "PreValidationFailed";
            result.Error = "Input file failed validation";
            results.Add(result);
            return;
        }

        string baseName = Path.GetFileNameWithoutExtension(inputFile);
        string tempPath = Path.Combine(config.OutputFolder, $"{baseName}.pdf");
        string archivePath = Path.Combine(config.ArchiveFolder, $"{baseName}.pdf");

        // Stage: Process with retry
        PdfDocument pdf = null;
        int attempt = 0;
        bool success = false;

        while (attempt < config.MaxRetries && !success)
        {
            attempt++;
            try
            {
                pdf = renderer.RenderHtmlFileAsPdf(inputFile);
                success = true;
            }
            catch (Exception ex) when (IsTransient(ex) && attempt < config.MaxRetries)
            {
                Thread.Sleep((int)Math.Pow(2, attempt) * 500);
            }
        }

        if (!success || pdf == null)
        {
            result.Status = "ProcessingFailed";
            result.Error = "Max retries exceeded";
            results.Add(result);
            return;
        }

        using (pdf)
        {
            // Stage: Compress and convert to PDF/A-3b for archival
            pdf.SaveAsPdfA(tempPath, PdfAVersions.PdfA3b);
        }

        // Stage: Post-validation
        if (!ValidateOutput(tempPath))
        {
            File.Move(tempPath, Path.Combine(config.ErrorFolder, $"{baseName}.pdf"), overwrite: true);
            result.Status = "PostValidationFailed";
            result.Error = "Output file failed validation";
            results.Add(result);
            return;
        }

        // Stage: Archive
        File.Move(tempPath, archivePath, overwrite: true);

        // Update checkpoint
        lock (checkpointLock)
        {
            checkpoint.CompletedFiles.Add(result.FileName);
            SaveCheckpoint(config.CheckpointPath, checkpoint);
        }

        result.Status = "Success";
        result.OutputSize = new FileInfo(archivePath).Length;
        result.EndTime = DateTime.UtcNow;
        results.Add(result);

        Console.WriteLine($"[OK] {baseName}.pdf ({result.OutputSize / 1024}KB)");
    }
    catch (Exception ex)
    {
        result.Status = "Error";
        result.Error = ex.Message;
        result.EndTime = DateTime.UtcNow;
        results.Add(result);
        Console.WriteLine($"[ERROR] {result.FileName}: {ex.Message}");
    }
});

stopwatch.Stop();

// Generate report
var report = new PipelineReport
{
    TotalFiles = allFiles.Length,
    ProcessedThisRun = results.Count,
    Succeeded = results.Count(r => r.Status == "Success"),
    PreValidationFailed = results.Count(r => r.Status == "PreValidationFailed"),
    ProcessingFailed = results.Count(r => r.Status == "ProcessingFailed"),
    PostValidationFailed = results.Count(r => r.Status == "PostValidationFailed"),
    Errors = results.Count(r => r.Status == "Error"),
    TotalDuration = stopwatch.Elapsed,
    AverageFileTime = results.Any() ? TimeSpan.FromMilliseconds(stopwatch.Elapsed.TotalMilliseconds / results.Count) : TimeSpan.Zero
};

string reportJson = JsonSerializer.Serialize(report, new JsonSerializerOptions { WriteIndented = true });
File.WriteAllText(config.ReportPath, reportJson);

Console.WriteLine($"\n=== Pipeline Complete ===");
Console.WriteLine($"Succeeded: {report.Succeeded}");
Console.WriteLine($"Failed: {report.PreValidationFailed + report.ProcessingFailed + report.PostValidationFailed + report.Errors}");
Console.WriteLine($"Duration: {report.TotalDuration.TotalMinutes:F1} minutes");
Console.WriteLine($"Report: {config.ReportPath}");

// Helper methods
bool ValidateInput(string path)
{
    try
    {
        var info = new FileInfo(path);
        if (!info.Exists || info.Length == 0 || info.Length > 50 * 1024 * 1024) return false;
        string content = File.ReadAllText(path);
        return content.Contains("<html", StringComparison.OrdinalIgnoreCase) ||
               content.Contains("<!DOCTYPE", StringComparison.OrdinalIgnoreCase);
    }
    catch { return false; }
}

bool ValidateOutput(string path)
{
    try
    {
        using var pdf = PdfDocument.FromFile(path);
        return pdf.PageCount > 0 && new FileInfo(path).Length > 1024;
    }
    catch { return false; }
}

bool IsTransient(Exception ex) =>
    ex is IOException || ex is OutOfMemoryException ||
    ex.Message.Contains("timeout", StringComparison.OrdinalIgnoreCase);

Checkpoint LoadCheckpoint(string path)
{
    if (File.Exists(path))
    {
        string json = File.ReadAllText(path);
        return JsonSerializer.Deserialize<Checkpoint>(json) ?? new Checkpoint();
    }
    return new Checkpoint();
}

void SaveCheckpoint(string path, Checkpoint cp) =>
    File.WriteAllText(path, JsonSerializer.Serialize(cp));


ata classes
s PipelineConfig

public string InputFolder { get; set; } = "";
public string OutputFolder { get; set; } = "";
public string ArchiveFolder { get; set; } = "";
public string ErrorFolder { get; set; } = "";
public string CheckpointPath { get; set; } = "";
public string ReportPath { get; set; } = "";
public int MaxConcurrency { get; set; }
public int MaxRetries { get; set; }
public int JpegQuality { get; set; }


s Checkpoint

public HashSet<string> CompletedFiles { get; set; } = new();


s ProcessingResult

public string FileName { get; set; } = "";
public string Status { get; set; } = "";
public string Error { get; set; } = "";
public long OutputSize { get; set; }
public DateTime StartTime { get; set; }
public DateTime EndTime { get; set; }


s PipelineReport

public int TotalFiles { get; set; }
public int ProcessedThisRun { get; set; }
public int Succeeded { get; set; }
public int PreValidationFailed { get; set; }
public int ProcessingFailed { get; set; }
public int PostValidationFailed { get; set; }
public int Errors { get; set; }
public TimeSpan TotalDuration { get; set; }
public TimeSpan AverageFileTime { get; set; }