PDF 与 PDF/A（比较及使用方法）

// Common XMLWorker limitations that require manual handling
public void ProcessComplexHTML(string htmlContent)
{
    // CSS flexbox -- not supported by XMLWorker
    if (htmlContent.Contains("display: flex"))
        throw new NotSupportedException("Flexbox layout not supported");

    // JavaScript content -- silently ignored
    if (htmlContent.Contains("<script>"))
        Console.WriteLine("Warning: JavaScript will be ignored");

    // 自定义字体 -- require manual embedding
    if (htmlContent.Contains("@font-face"))
        Console.WriteLine("Warning: Web fonts need manual setup");
}

' Common XMLWorker limitations that require manual handling
Public Sub ProcessComplexHTML(htmlContent As String)
    ' CSS flexbox -- not supported by XMLWorker
    If htmlContent.Contains("display: flex") Then
        Throw New NotSupportedException("Flexbox layout not supported")
    End If

    ' JavaScript content -- silently ignored
    If htmlContent.Contains("<script>") Then
        Console.WriteLine("Warning: JavaScript will be ignored")
    End If

    ' 自定义字体 -- require manual embedding
    If htmlContent.Contains("@font-face") Then
        Console.WriteLine("Warning: Web fonts need manual setup")
    End If
End Sub

using IronPdf;

ChromePdfRenderer renderer = new ChromePdfRenderer();

// Configure rendering options for production use
renderer.RenderingOptions.MarginTop = 40;
renderer.RenderingOptions.MarginBottom = 40;
renderer.RenderingOptions.CssMediaType = PdfCssMediaType.Print;
renderer.RenderingOptions.PrintHtmlBackgrounds = true;

string html = @"<div style='font-family: Arial; width: 100%;'>
    <h1 style='color: #2e6c80;'>Invoice #12345</h1>
    <table style='width: 100%; border-collapse: collapse;'>
        <tr>
            <th style='border: 1px solid #ddd; padding: 8px;'>Item</th>
            <th style='border: 1px solid #ddd; padding: 8px;'>Price</th>
        </tr>
        <tr>
            <td style='border: 1px solid #ddd; padding: 8px;'>Service</td>
            <td style='border: 1px solid #ddd; padding: 8px;'>$100.00</td>
        </tr>
    </table>
</div>";

PdfDocument pdf = renderer.RenderHtmlAsPdf(html);
pdf.SaveAs("invoice.pdf");

Imports IronPdf

Dim renderer As New ChromePdfRenderer()

' Configure rendering options for production use
renderer.RenderingOptions.MarginTop = 40
renderer.RenderingOptions.MarginBottom = 40
renderer.RenderingOptions.CssMediaType = PdfCssMediaType.Print
renderer.RenderingOptions.PrintHtmlBackgrounds = True

Dim html As String = "<div style='font-family: Arial; width: 100%;'>" & _
    "<h1 style='color: #2e6c80;'>Invoice #12345</h1>" & _
    "<table style='width: 100%; border-collapse: collapse;'>" & _
        "<tr>" & _
            "<th style='border: 1px solid #ddd; padding: 8px;'>Item</th>" & _
            "<th style='border: 1px solid #ddd; padding: 8px;'>Price</th>" & _
        "</tr>" & _
        "<tr>" & _
            "<td style='border: 1px solid #ddd; padding: 8px;'>Service</td>" & _
            "<td style='border: 1px solid #ddd; padding: 8px;'>$100.00</td>" & _
        "</tr>" & _
    "</table>" & _
"</div>"

Dim pdf As PdfDocument = renderer.RenderHtmlAsPdf(html)
pdf.SaveAs("invoice.pdf")

using IronPdf;
using Microsoft.Extensions.Logging;

// Production-ready PDF generation with IronPDF
public class PdfGenerator
{
    private readonly ChromePdfRenderer _renderer;
    private readonly ILogger<PdfGenerator> _logger;

    public PdfGenerator(ILogger<PdfGenerator> logger)
    {
        _logger = logger;
        _renderer = new ChromePdfRenderer();
        _renderer.RenderingOptions.Timeout = 60;
        _renderer.RenderingOptions.EnableJavaScript = true;
        _renderer.RenderingOptions.RenderDelay = 2000;
        _renderer.RenderingOptions.HtmlHeader = new HtmlHeaderFooter
        {
            Height = 25,
            HtmlFragment = "<div style='text-align: center;'>{page} of {total-pages}</div>"
        };
    }

    public async Task<PdfDocument> GenerateWithRetry(string html, int maxRetries = 3)
    {
        for (int i = 0; i < maxRetries; i++)
        {
            try
            {
                _logger.LogInformation("Generating PDF, attempt {Attempt}", i + 1);
                return await _renderer.RenderHtmlAsPdfAsync(html);
            }
            catch (Exception ex)
            {
                _logger.LogWarning("PDF generation failed: {Message}", ex.Message);
                if (i == maxRetries - 1) throw;
                await Task.Delay(1000 * (i + 1));
            }
        }
        throw new InvalidOperationException("PDF generation failed after retries");
    }
}

Imports IronPdf
Imports Microsoft.Extensions.Logging

' Production-ready PDF generation with IronPDF
Public Class PdfGenerator
    Private ReadOnly _renderer As ChromePdfRenderer
    Private ReadOnly _logger As ILogger(Of PdfGenerator)

    Public Sub New(logger As ILogger(Of PdfGenerator))
        _logger = logger
        _renderer = New ChromePdfRenderer()
        _renderer.RenderingOptions.Timeout = 60
        _renderer.RenderingOptions.EnableJavaScript = True
        _renderer.RenderingOptions.RenderDelay = 2000
        _renderer.RenderingOptions.HtmlHeader = New HtmlHeaderFooter With {
            .Height = 25,
            .HtmlFragment = "<div style='text-align: center;'>{page} of {total-pages}</div>"
        }
    End Sub

    Public Async Function GenerateWithRetry(html As String, Optional maxRetries As Integer = 3) As Task(Of PdfDocument)
        For i As Integer = 0 To maxRetries - 1
            Try
                _logger.LogInformation("Generating PDF, attempt {Attempt}", i + 1)
                Return Await _renderer.RenderHtmlAsPdfAsync(html)
            Catch ex As Exception
                _logger.LogWarning("PDF generation failed: {Message}", ex.Message)
                If i = maxRetries - 1 Then Throw
                Await Task.Delay(1000 * (i + 1))
            End Try
        Next
        Throw New InvalidOperationException("PDF generation failed after retries")
    End Function
End Class

// Before (iTextSharp) -- error-prone approach requiring workarounds
public byte[] CreatePdfWithIText(string htmlContent)
{
    using var ms = new MemoryStream();
    var document = new Document();
    var writer = PdfWriter.GetInstance(document, ms);
    document.Open();

    // Must add empty paragraph to avoid "no pages" error
    document.Add(new Paragraph(""));

    try
    {
        using var sr = new StringReader(htmlContent);
        XMLWorkerHelper.GetInstance().ParseXHtml(writer, document, sr);
    }
    catch (Exception ex)
    {
        document.Add(new Paragraph("Error: " + ex.Message));
    }

    document.Close();
    return ms.ToArray();
}

// After (IronPDF) -- reliable, no workarounds needed
public byte[] CreatePdfWithIron(string htmlContent)
{
    ChromePdfRenderer renderer = new ChromePdfRenderer();
    renderer.RenderingOptions.EnableJavaScript = true;
    renderer.RenderingOptions.RenderDelay = 500;

    PdfDocument pdf = renderer.RenderHtmlAsPdf(htmlContent);
    return pdf.BinaryData;
}

Imports System.IO
Imports iTextSharp.text
Imports iTextSharp.text.pdf
Imports iTextSharp.tool.xml

Public Class PdfCreator

    ' Before (iTextSharp) -- error-prone approach requiring workarounds
    Public Function CreatePdfWithIText(htmlContent As String) As Byte()
        Using ms As New MemoryStream()
            Dim document As New Document()
            Dim writer As PdfWriter = PdfWriter.GetInstance(document, ms)
            document.Open()

            ' Must add empty paragraph to avoid "no pages" error
            document.Add(New Paragraph(""))

            Try
                Using sr As New StringReader(htmlContent)
                    XMLWorkerHelper.GetInstance().ParseXHtml(writer, document, sr)
                End Using
            Catch ex As Exception
                document.Add(New Paragraph("Error: " & ex.Message))
            End Try

            document.Close()
            Return ms.ToArray()
        End Using
    End Function

    ' After (IronPDF) -- reliable, no workarounds needed
    Public Function CreatePdfWithIron(htmlContent As String) As Byte()
        Dim renderer As New ChromePdfRenderer()
        renderer.RenderingOptions.EnableJavaScript = True
        renderer.RenderingOptions.RenderDelay = 500

        Dim pdf As PdfDocument = renderer.RenderHtmlAsPdf(htmlContent)
        Return pdf.BinaryData
    End Function

End Class