C# Windows窗体Panel转PDF遇依赖问题，求替代实现方案

希望将WinForms窗体中的Panel控件内容导出为PDF文件，尝试用iText7编写了代码，但运行时抛出异常，安装相关依赖时又出现大量错误，寻求其他实现Panel转PDF的方案。

所用代码 #

using System;
using System.Data;
using System.Windows.Forms;
using iText.Kernel.Pdf;
using iText.Layout;
using iText.Layout.Element;
using iText.IO.Image;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;

namespace PDFGeneratorApp
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        
        private void buttonPrintPDF_Click(object sender, EventArgs e)
        {
            Panel myPanel = panel1;
            string filePath = "file.pdf";
            ExportPanelToPdf(panel1, filePath);
        }

        public static void ExportPanelToPdf(Panel panel, string filePath)
        {
            // 先将Panel捕获为位图
            Bitmap bitmap = new Bitmap(panel.Width, panel.Height);
            panel.DrawToBitmap(bitmap, new Rectangle(0, 0, panel.Width, panel.Height));

            // 将图像保存到流
            using (MemoryStream stream = new MemoryStream())
            {
                bitmap.Save(stream, ImageFormat.Png);
                byte[] imageBytes = stream.ToArray();

                // 创建PDF文档
                PdfWriter writer = new PdfWriter(filePath);
                PdfDocument pdf = new PdfDocument(writer);
                Document document = new Document(pdf);

                // 将图像添加到PDF
                ImageData imageData = ImageDataFactory.Create(imageBytes);
                iText.Layout.Element.Image image = new iText.Layout.Element.Image(imageData);

                document.Add(image);

                // 关闭文档
                document.Close();
            }
        }
    }
}

抛出的异常 #

iText.Kernel.Exceptions.PdfException
HResult=0x80131500
Message=Unknown PdfException.
Source=itext.kernel
StackTrace:
at iText.Kernel.Pdf.SmartModePdfObjectsSerializer..ctor()
at iText.Kernel.Pdf.PdfWriter..ctor(Stream os, WriterProperties properties)
at iText.Kernel.Pdf.PdfWriter..ctor(String filename)
at PDFGeneratorApp.Form1.ExportPanelToPdf(Panel panel, String filePath) in C:\Users\CONSULTANT 2\source\repos\PDFGeneratorApp\Form1.cs:line 62
at PDFGeneratorApp.Form1.buttonPrintPDF_Click(Object sender, EventArgs e) in C:\Users\CONSULTANT 2\source\repos\PDFGeneratorApp\Form1.cs:line 46
at System.Windows.Forms.Control.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ButtonBase.WndProc(Message& m)
at System.Windows.Forms.Button.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.Run(Form mainForm)
at PDFGeneratorApp.Program.Main() in C:\Users\CONSULTANT 2\source\repos\PDFGeneratorApp\Program.cs:line 19

最初抛出异常的调用栈：
iText.Bouncycastleconnector.BouncyCastleDefaultFactory.CreateIDigest(string)
iText.Kernel.Pdf.SmartModePdfObjectsSerializer.SmartModePdfObjectsSerializer()

内部异常1：

NotSupportedException: Either com.itextpdf:bouncy-castle-adapter or com.itextpdf:bouncy-castle-fips-adapter dependency must be added in order to use BouncyCastleFactoryCreator

方案1：使用PdfSharp（免费开源） #

PdfSharp是.NET平台下的开源PDF库，无需额外加密依赖，操作简单。核心思路是先将Panel转为位图，再把位图插入PDF。

实现步骤： #

1. 通过NuGet安装PdfSharp包（选择适配.NET Framework的版本）。
2. 替换导出代码：

using PdfSharp.Drawing;
using PdfSharp.Pdf;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Windows.Forms;

public static void ExportPanelToPdf(Panel panel, string filePath)
{
    // 捕获Panel为位图
    Bitmap bitmap = new Bitmap(panel.Width, panel.Height);
    panel.DrawToBitmap(bitmap, new Rectangle(0, 0, panel.Width, panel.Height));

    // 将位图转为PdfSharp可用的XImage
    using (MemoryStream ms = new MemoryStream())
    {
        bitmap.Save(ms, ImageFormat.Png);
        ms.Position = 0;
        XImage xImage = XImage.FromStream(ms);

        // 创建PDF文档并设置页面尺寸匹配Panel
        PdfDocument document = new PdfDocument();
        PdfPage page = document.AddPage();
        page.Width = XUnit.FromPixels(bitmap.Width);
        page.Height = XUnit.FromPixels(bitmap.Height);

        // 将图像绘制到PDF页面
        XGraphics gfx = XGraphics.FromPdfPage(page);
        gfx.DrawImage(xImage, 0, 0, page.Width, page.Height);

        // 保存并关闭文档
        document.Save(filePath);
        document.Close();
    }
}

方案2：WinForms打印系统+虚拟PDF打印机 #

利用WinForms自带的PrintDocument控件，结合系统自带的虚拟PDF打印机（如Microsoft Print to PDF），直接将Panel内容"打印"为PDF，无需额外第三方库。

实现步骤： #

1. 在窗体中添加PrintDocument控件（命名为printDocument1）。
2. 编写导出逻辑：

private void buttonPrintPDF_Click(object sender, EventArgs e)
{
    PrintDialog printDialog = new PrintDialog();
    printDialog.Document = printDocument1;
    // 强制选择Microsoft Print to PDF（也可让用户自行选择）
    printDialog.PrinterSettings.PrinterName = "Microsoft Print to PDF";
    
    if (printDialog.ShowDialog() == DialogResult.OK)
    {
        // 绑定打印事件，绘制Panel内容
        printDocument1.PrintPage += (s, args) =>
        {
            Bitmap bitmap = new Bitmap(panel1.Width, panel1.Height);
            panel1.DrawToBitmap(bitmap, new Rectangle(0, 0, panel1.Width, panel1.Height));
            // 按页面尺寸缩放绘制图像
            args.Graphics.DrawImage(bitmap, args.PageBounds);
        };
        
        // 执行打印，输出为PDF文件
        printDocument1.Print();
    }
}

注意：Windows 10及以上系统默认自带Microsoft Print to PDF，若未安装可在「设置-应用-可选功能」中添加。

方案3：使用Spire.PDF免费版 #

Spire.PDF免费版功能足够满足简单的图像转PDF需求，无需处理复杂依赖。

实现步骤： #

1. 通过NuGet安装FreeSpire.PDF包。
2. 编写导出代码：

using Spire.Pdf;
using Spire.Pdf.Graphics;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Windows.Forms;

public static void ExportPanelToPdf(Panel panel, string filePath)
{
    Bitmap bitmap = new Bitmap(panel.Width, panel.Height);
    panel.DrawToBitmap(bitmap, new Rectangle(0, 0, panel.Width, panel.Height));

    // 创建PDF文档并设置页面尺寸
    PdfDocument doc = new PdfDocument();
    PdfPage page = doc.Pages.Add(new SizeF(bitmap.Width, bitmap.Height));
    PdfCanvas canvas = new PdfCanvas(page);

    // 将位图转为PdfImage并绘制到页面
    using (MemoryStream ms = new MemoryStream())
    {
        bitmap.Save(ms, ImageFormat.Png);
        PdfImage image = PdfImage.FromStream(ms);
        canvas.DrawImage(image, 0, 0, bitmap.Width, bitmap.Height);
    }

    // 保存PDF
    doc.SaveToFile(filePath);
    doc.Close();
}

内容的提问来源于stack exchange，提问作者Hex Heager