.NET 的免费 PDF 库：C# 中的隐藏成本和更好的替代方案

var document = new PdfDocument();
var page = document.AddPage();
var gfx = XGraphics.FromPdfPage(page);

// Every element needs manual coordinates
var titleFont = new XFont("Arial", 18, XFontStyleEx.Bold);
var bodyFont = new XFont("Arial", 10);

gfx.DrawString("INVOICE #2024-0847", titleFont, XBrushes.Black, 72, 72);
gfx.DrawString("Date: 2024-12-15", bodyFont, XBrushes.Gray, 72, 100);

// Table header - manual line drawing
gfx.DrawLine(XPens.Black, 72, 140, 540, 140);
gfx.DrawString("Item", bodyFont, XBrushes.Black, 72, 155);
gfx.DrawString("Qty", bodyFont, XBrushes.Black, 300, 155);
gfx.DrawString("Price", bodyFont, XBrushes.Black, 400, 155);
gfx.DrawLine(XPens.Black, 72, 170, 540, 170);

// Row data - every cell is a manual coordinate
gfx.DrawString("Annual License", bodyFont, XBrushes.Black, 72, 185);
gfx.DrawString("1", bodyFont, XBrushes.Black, 300, 185);
gfx.DrawString("$749.00", bodyFont, XBrushes.Black, 400, 185);

document.Save("invoice.pdf");

Imports PdfSharp.Pdf
Imports PdfSharp.Drawing

Dim document As New PdfDocument()
Dim page As PdfPage = document.AddPage()
Dim gfx As XGraphics = XGraphics.FromPdfPage(page)

' Every element needs manual coordinates
Dim titleFont As New XFont("Arial", 18, XFontStyleEx.Bold)
Dim bodyFont As New XFont("Arial", 10)

gfx.DrawString("INVOICE #2024-0847", titleFont, XBrushes.Black, 72, 72)
gfx.DrawString("Date: 2024-12-15", bodyFont, XBrushes.Gray, 72, 100)

' Table header - manual line drawing
gfx.DrawLine(XPens.Black, 72, 140, 540, 140)
gfx.DrawString("Item", bodyFont, XBrushes.Black, 72, 155)
gfx.DrawString("Qty", bodyFont, XBrushes.Black, 300, 155)
gfx.DrawString("Price", bodyFont, XBrushes.Black, 400, 155)
gfx.DrawLine(XPens.Black, 72, 170, 540, 170)

' Row data - every cell is a manual coordinate
gfx.DrawString("Annual License", bodyFont, XBrushes.Black, 72, 185)
gfx.DrawString("1", bodyFont, XBrushes.Black, 300, 185)
gfx.DrawString("$749.00", bodyFont, XBrushes.Black, 400, 185)

document.Save("invoice.pdf")

Document.Create(container =>
{
    container.Page(page =>
    {
        page.Size(PageSizes.A4);
        page.Margin(2, Unit.Centimetre);

        page.Content().Column(column =>
        {
            column.Item().Text("Invoice #2024-0847").FontSize(18).Bold();
            column.Item().Table(table =>
            {
                table.ColumnsDefinition(columns =>
                {
                    columns.RelativeColumn(3);
                    columns.RelativeColumn(1);
                    columns.RelativeColumn(1);
                });

                table.Cell().Text("Item").Bold();
                table.Cell().Text("Qty").Bold();
                table.Cell().Text("Price").Bold();

                table.Cell().Text("Annual License");
                table.Cell().Text("1");
                table.Cell().Text("$749.00");
            });
        });
    });
}).GeneratePdf("invoice.pdf");

Document.Create(Sub(container)
    container.Page(Sub(page)
        page.Size(PageSizes.A4)
        page.Margin(2, Unit.Centimetre)

        page.Content().Column(Sub(column)
            column.Item().Text("Invoice #2024-0847").FontSize(18).Bold()
            column.Item().Table(Sub(table)
                table.ColumnsDefinition(Sub(columns)
                    columns.RelativeColumn(3)
                    columns.RelativeColumn(1)
                    columns.RelativeColumn(1)
                End Sub)

                table.Cell().Text("Item").Bold()
                table.Cell().Text("Qty").Bold()
                table.Cell().Text("Price").Bold()

                table.Cell().Text("Annual License")
                table.Cell().Text("1")
                table.Cell().Text("$749.00")
            End Sub)
        End Sub)
    End Sub)
End Sub).GeneratePdf("invoice.pdf")

using PuppeteerSharp;

public class PuppeteerPdfService : IDisposable
{
    private IBrowser _browser;
    private readonly SemaphoreSlim _semaphore;
    private long _pdfCount = 0;

    public PuppeteerPdfService()
    {
        // Limit concurrent pages to prevent memory exhaustion
        _semaphore = new SemaphoreSlim(3, 3);
    }

    public async Task InitializeAsync()
    {
        // Step 1: Download Chromium binary (~280MB)
        var fetcher = new BrowserFetcher();
        await fetcher.DownloadAsync();

        // Step 2: Launch with production-hardened flags
        _browser = await Puppeteer.LaunchAsync(new LaunchOptions
        {
            Headless = true,
            Args = new[]
            {
                "--no-sandbox",              // Required in Docker
                "--disable-setuid-sandbox",  // Required in Docker
                "--disable-dev-shm-usage",   // Prevent /dev/shm exhaustion
                "--disable-gpu",
                "--no-zygote",
                "--single-process",
                "--disable-extensions",
                "--max_old_space_size=4096"
            },
            Timeout = 30000
        });
    }

    public async Task<byte[]> GeneratePdfAsync(string html)
    {
        await _semaphore.WaitAsync();
        IPage page = null;

        try
        {
            Interlocked.Increment(ref _pdfCount);
            page = await _browser.NewPageAsync();

            await page.SetContentAsync(html, new NavigationOptions
            {
                WaitUntil = new[] { WaitUntilNavigation.Networkidle0 },
                Timeout = 20000
            });

            var pdfBytes = await page.PdfAsync(new PdfOptions
            {
                Format = PaperFormat.A4,
                PrintBackground = true,
                MarginOptions = new MarginOptions
                {
                    Top = "20mm", Bottom = "20mm",
                    Left = "15mm", Right = "15mm"
                }
            });

            return pdfBytes;
        }
        finally
        {
            if (page != null)
            {
                try { await page.CloseAsync(); }
                catch { /* Disposal can hang — GitHub issue #1489 */ }
            }
            _semaphore.Release();
        }
    }

    // Restart browser periodically to reclaim leaked memory
    public async Task RecycleBrowserAsync()
    {
        var oldBrowser = _browser;
        await InitializeAsync();
        try { oldBrowser?.Dispose(); } catch { }
    }

    public void Dispose()
    {
        _browser?.Dispose();
        _semaphore?.Dispose();
    }
}

Imports PuppeteerSharp
Imports System.Threading

Public Class PuppeteerPdfService
    Implements IDisposable

    Private _browser As IBrowser
    Private ReadOnly _semaphore As SemaphoreSlim
    Private _pdfCount As Long = 0

    Public Sub New()
        ' Limit concurrent pages to prevent memory exhaustion
        _semaphore = New SemaphoreSlim(3, 3)
    End Sub

    Public Async Function InitializeAsync() As Task
        ' Step 1: Download Chromium binary (~280MB)
        Dim fetcher = New BrowserFetcher()
        Await fetcher.DownloadAsync()

        ' Step 2: Launch with production-hardened flags
        _browser = Await Puppeteer.LaunchAsync(New LaunchOptions With {
            .Headless = True,
            .Args = {
                "--no-sandbox",              ' Required in Docker
                "--disable-setuid-sandbox",  ' Required in Docker
                "--disable-dev-shm-usage",   ' Prevent /dev/shm exhaustion
                "--disable-gpu",
                "--no-zygote",
                "--single-process",
                "--disable-extensions",
                "--max_old_space_size=4096"
            },
            .Timeout = 30000
        })
    End Function

    Public Async Function GeneratePdfAsync(html As String) As Task(Of Byte())
        Await _semaphore.WaitAsync()
        Dim page As IPage = Nothing

        Try
            Interlocked.Increment(_pdfCount)
            page = Await _browser.NewPageAsync()

            Await page.SetContentAsync(html, New NavigationOptions With {
                .WaitUntil = {WaitUntilNavigation.Networkidle0},
                .Timeout = 20000
            })

            Dim pdfBytes = Await page.PdfAsync(New PdfOptions With {
                .Format = PaperFormat.A4,
                .PrintBackground = True,
                .MarginOptions = New MarginOptions With {
                    .Top = "20mm", .Bottom = "20mm",
                    .Left = "15mm", .Right = "15mm"
                }
            })

            Return pdfBytes
        Finally
            If page IsNot Nothing Then
                Try
                    Await page.CloseAsync()
                Catch
                    ' Disposal can hang — GitHub issue #1489
                End Try
            End If
            _semaphore.Release()
        End Try
    End Function

    ' Restart browser periodically to reclaim leaked memory
    Public Async Function RecycleBrowserAsync() As Task
        Dim oldBrowser = _browser
        Await InitializeAsync()
        Try
            oldBrowser?.Dispose()
        Catch
        End Try
    End Function

    Public Sub Dispose() Implements IDisposable.Dispose
        _browser?.Dispose()
        _semaphore?.Dispose()
    End Sub
End Class