c# - SelectPDF.Document.Footer 始终为空？

Question

从 HTTP 请求流创建 PDF 文档。

public class HomeController : Controller {
    public HomeController() {
        converter = new HtmlToPdf();
        InitializeConverter();
    }

    public void Index() {
        ConvertHtmlToPdf(new Uri("http://localhost:52328/CertificateOfOrigin?noCertificate=2691"));
    }

    public void ConvertHtmlToPdf(Uri toConvert) {
        if(toConvert == null) throw new ArgumentNullException(nameof(toConvert));
        using(var stream =new MemoryStream()) {
            var doc = converter.ConvertUrl(toConvert.AbsoluteUri);
            // The doc.AddTemplate returns a PdfTemplate and should be assigned to doc.Footer
            doc.Footer = doc.AddTemplate(doc.Pages[0].ClientRectangle.Width, 100);
            var pageNumbering = new PdfTextElement(20, 50, "Page {page_number} of {total_pages}", doc.Fonts[0], Color.Black);
            // Once template defined, I add it to the doc Footer. But...
            doc.Footer.Add(pageNumbering); // Throws a NullPointerException?
            doc.Footer = template;
            doc.Save(stream);
            doc.Close();

            using(var ms = new MemoryStream(stream.ToArray())) {
                Response.AddHeader("content-disposition", "filename=certificate-of-origin.pdf");
                Response.ContentType = "application/pdf";
                ms.CopyTo(Response.OutputStream);
                Response.End();
                Response.Close();
            }
        }
    }

    private void InitializeConverter() {
        converter.Options.MarginBottom = 0;
        converter.Options.MarginLeft = 0;
        converter.Options.MarginRight = 0;
        converter.Options.MarginTop = 0;
        converter.Options.PdfPageSize = PdfPageSize.Letter;
    }

    private readonly HtmlToPdf converter;
}

我放了一个断点并快速查看了 doc.AddTemplate 方法调用的返回，它返回了一个实际的 PdfTemplate 没问题！

除此之外，一切正常。文档生成没有问题，除非我取消注释页码，因为 doc.Footer 尽管分配了它，但它仍然为空。

这可能是一个错误吗？同上。

标签： c#.netpdfpdf-generationselectpdf

Answer 1

您需要在转换之前设置页眉/页脚内容，如下所示： https ://selectpdf.com/demo-mvc/HtmlToPdfHeadersAndFooters

using System;
using System.Web.Mvc;

namespace SelectPdf.Samples.Controllers
{
    public class HtmlToPdfHeadersAndFootersController : Controller
    {
        // GET: HtmlToPdfHeadersAndFooters
        public ActionResult Index()
        {
            return View();
        }

        [HttpPost]
        public ActionResult SubmitAction(FormCollection collection)
        {
            // get parameters
            string headerUrl = Server.MapPath("~/files/header.html");
            string footerUrl = Server.MapPath("~/files/footer.html");

            bool showHeaderOnFirstPage = collection["ChkHeaderFirstPage"] == "on";
            bool showHeaderOnOddPages = collection["ChkHeaderOddPages"] == "on";
            bool showHeaderOnEvenPages = collection["ChkHeaderEvenPages"] == "on";

            int headerHeight = 50;
            try
            {
                headerHeight = Convert.ToInt32(collection["TxtHeaderHeight"]);
            }
            catch { }

            bool showFooterOnFirstPage = collection["ChkFooterFirstPage"] == "on";
            bool showFooterOnOddPages = collection["ChkFooterOddPages"] == "on";
            bool showFooterOnEvenPages = collection["ChkFooterEvenPages"] == "on"; 

            int footerHeight = 50;
            try
            {
                footerHeight = Convert.ToInt32(collection["TxtFooterHeight"]);
            }
            catch { }

            // instantiate a html to pdf converter object
            HtmlToPdf converter = new HtmlToPdf();

            // header settings
            converter.Options.DisplayHeader = showHeaderOnFirstPage ||
                showHeaderOnOddPages || showHeaderOnEvenPages;
            converter.Header.DisplayOnFirstPage = showHeaderOnFirstPage;
            converter.Header.DisplayOnOddPages = showHeaderOnOddPages;
            converter.Header.DisplayOnEvenPages = showHeaderOnEvenPages;
            converter.Header.Height = headerHeight;

            PdfHtmlSection headerHtml = new PdfHtmlSection(headerUrl);
            headerHtml.AutoFitHeight = HtmlToPdfPageFitMode.AutoFit;
            converter.Header.Add(headerHtml);

            // footer settings
            converter.Options.DisplayFooter = showFooterOnFirstPage ||
                showFooterOnOddPages || showFooterOnEvenPages;
            converter.Footer.DisplayOnFirstPage = showFooterOnFirstPage;
            converter.Footer.DisplayOnOddPages = showFooterOnOddPages;
            converter.Footer.DisplayOnEvenPages = showFooterOnEvenPages;
            converter.Footer.Height = footerHeight;

            PdfHtmlSection footerHtml = new PdfHtmlSection(footerUrl);
            footerHtml.AutoFitHeight = HtmlToPdfPageFitMode.AutoFit;
            converter.Footer.Add(footerHtml);

            // add page numbering element to the footer
            if (collection["ChkPageNumbering"] == "on")
            {
                // page numbers can be added using a PdfTextSection object
                PdfTextSection text = new PdfTextSection(0, 10,
                    "Page: {page_number} of {total_pages}  ",
                    new System.Drawing.Font("Arial", 8));
                text.HorizontalAlign = PdfTextHorizontalAlign.Right;
                converter.Footer.Add(text);
            }

            // create a new pdf document converting an url
            PdfDocument doc = converter.ConvertUrl(collection["TxtUrl"]);

            // custom header on page 3
            if (doc.Pages.Count >= 3)
            {
                PdfPage page = doc.Pages[2];

                PdfTemplate customHeader = doc.AddTemplate(
                    page.PageSize.Width, headerHeight);
                PdfHtmlElement customHtml = new PdfHtmlElement(
                    "<div><b>This is the custom header that will " +
                    "appear only on page 3!</b></div>",
                    string.Empty);
                customHeader.Add(customHtml);

                page.CustomHeader = customHeader;
            }

            // save pdf document
            byte[] pdf = doc.Save();

            // close pdf document
            doc.Close();

            // return resulted pdf document
            FileResult fileResult = new FileContentResult(pdf, "application/pdf");
            fileResult.FileDownloadName = "Document.pdf";
            return fileResult;
        }
    }
}

或者使用这种方法，将页眉/页脚添加到已生成的 pdf 中： https ://selectpdf.com/demo-mvc/ExistingPdfHeadersAndFooters

using System.Web.Mvc;
using System.Drawing;

namespace SelectPdf.Samples.Controllers
{
    public class ExistingPdfHeadersAndFootersController : Controller
    {
        // GET: ExistingPdfHeadersAndFooters
        public ActionResult Index()
        {
            return View();
        }

        [HttpPost]
        public ActionResult SubmitAction(FormCollection collection)
        {
            // the test file
            string filePdf = Server.MapPath("~/files/selectpdf.pdf");
            string imgFile = Server.MapPath("~/files/logo.png");

            // resize the content
            PdfResizeManager resizer = new PdfResizeManager();
            resizer.Load(filePdf);

            // add extra top and bottom margins
            resizer.PageMargins = new PdfMargins(0, 0, 90, 40);

            // add the header and footer to the existing (now resized pdf document)
            PdfDocument doc = resizer.GetDocument();

            // header template (90 points in height) with image element
            PdfTemplate header = doc.AddTemplate(doc.Pages[0].ClientRectangle.Width, 90);
            PdfImageElement img1 = new PdfImageElement(10, 10, imgFile);
            header.Add(img1);

            // footer template (40 points in height) with text element
            PdfTemplate footer = doc.AddTemplate(new RectangleF(0,
                doc.Pages[0].ClientRectangle.Height - 40,
                doc.Pages[0].ClientRectangle.Width, 40));

            // create a new pdf font
            PdfFont font2 = doc.AddFont(PdfStandardFont.Helvetica);
            font2.Size = 12;

            PdfTextElement text1 = new PdfTextElement(10, 10,
                "Generated by SelectPdf. Page number {page_number} of {total_pages}.",
            font2);
            text1.ForeColor = System.Drawing.Color.Blue;
            footer.Add(text1);

            // save pdf document
            byte[] pdf = doc.Save();

            // close pdf document
            resizer.Close();

            // return resulted pdf document
            FileResult fileResult = new FileContentResult(pdf, "application/pdf");
            fileResult.FileDownloadName = "Document.pdf";
            return fileResult;
        }
    }    
}

最好的方法是第一种，因此请尝试在转换之前移动页脚设置。