c# - MigraDoc PDF 渲染器遇到 System.NullReferenceException

Question

我在 Azure 上使用 MigraDoc 和 PDF 渲染器，但它抛出了 System.NullReferenceException。这是异常(exception):

System.NullReferenceException: Object reference not set to an instance of an object.
at PdfSharp.Fonts.OpenType.OpenTypeFontface.CetOrCreateFrom(XFontSource fontSource)
at PdfSharp.Drawing.XGlyphTypeface.GetOrCreateFrom(String familyName, FontResolvingOptions fontResolvingOptions)
at PdfSharp.Drawing.XFont.Initialize()
at MigraDoc.Rendering.FontHandler.FontToXFont(Font font, PdfFontEncoding encoding)
at MigraDoc.Rendering.ParagraphRenderer.get_CurrentFont()
at MigraDoc.Rendering.ParagraphRenderer.InitFormat(Area area, FormatInfo previousFormatInfo)
at MigraDoc.Rendering.ParagraphRenderer.Format(Area area, FormatInfo previousFormatInfo)
at MigraDoc.Rendering.TopDownFormatter.FormatOnAreas(XGraphics gfx, Boolean topLevel)
at MigraDoc.Rendering.FormattedDocument.Format(XGraphics gfx)
at MigraDoc.Rendering.DocumentRenderer.PrepareDocument()
at MigraDoc.Rendering.PdfDocumentRenderer.PrepareDocumentRenderer(Boolean prepareCompletely)
at MigraDoc.Rendering.PdfDocumentRenderer.PrepareRenderPages()
at MigraDoc.Rendering.PdfDocumentRenderer.RenderDocument()
at EmailQueue.AddCopyToEFolder.<Run>d__3.MoveNext()

这是我在出现问题时使用的代码。 document 属于 MigraDoc.DocumentObjectModel.Document 类，并且已填充文本。

PdfDocumentRenderer pdf = new PdfDocumentRenderer(true);
MemoryStream stream = new MemoryStream();
pdf.Document = document;
pdf.RenderDocument(); //<-- This is where the exception occurs
pdf.Save(stream, false);

编辑:我已经实现了 MyFontResolver 类，如下所示，并且我正在使用 GlobalFontSettings.FontResolver = new MyFontResolver();在我的代码中将字体解析器设置为类

public class MyFontResolver : IFontResolver
    {
        public FontResolverInfo ResolveTypeface(string familyName, bool isBold, bool isItalic)
        {
            // Ignore case of font names.
            var name = familyName.ToLower();

            // Deal with the fonts we know.
            switch (name)
            {
                case "ubuntu":
                    if (isBold)
                    {
                        if (isItalic)
                            return new FontResolverInfo("Ubuntu#bi");
                        return new FontResolverInfo("Ubuntu#b");
                    }
                    if (isItalic)
                        return new FontResolverInfo("Ubuntu#i");
                    return new FontResolverInfo("Ubuntu#");

                case "janitor":
                    return new FontResolverInfo("Janitor#");
            }

            // We pass all other font requests to the default handler.
            // When running on a web server without sufficient permission, you can return a default font at this stage.
            return PlatformFontResolver.ResolveTypeface(familyName, isBold, isItalic);
        }

        private byte[] LoadFontData(string name)
        {
            var assembly = Assembly.GetExecutingAssembly();

            // Test code to find the names of embedded fonts - put a watch on "ourResources"
            //var ourResources = assembly.GetManifestResourceNames();

            using (Stream stream = assembly.GetManifestResourceStream(name))
            {
                if (stream == null)
                    throw new ArgumentException("No resource with name " + name);

                int count = (int)stream.Length;
                byte[] data = new byte[count];
                stream.Read(data, 0, count);
                return data;
            }
        }

        public byte[] GetFont(string faceName)
        {
            switch (faceName)
            {
                case "Arial#":
                    return LoadFontData("MyProject.fonts.arial.arial.ttf"); ;

                case "Arial#b":
                    return LoadFontData("MyProject.fonts.arial.arialbd.ttf"); ;

                case "Arial#i":
                    return LoadFontData("MyProject.fonts.arial.ariali.ttf");

                case "Arial#bi":
                    return LoadFontData("MyProject.fonts.arial.arialbi.ttf");
            }

            return null;
        }
    }

我现在收到一个单独的错误，我认为我的字体解析器应该修复该错误

System.InvalidOperationException: Microsoft Azure returns STATUS_ACCESS_DENIED ((NTSTATUS)0xC0000022L) from GetFontData. This is a bug in Azure. You must implement a FontResolver to circumvent this issue.
at PdfSharp.Drawing.XFontSource.ReadFontBytesFromGdi(Font gdiFont)
at PdfSharp.Fonts.PlatformFontResolver.CreateFontSource(String familyName, FontResolvingOptions fontResolvingOptions, Font& font, String typefaceKey)
at PdfSharp.Fonts.PlatformFontResolver.ResolveTypeface(String familyName, FontResolvingOptions fontResolvingOptions, String typefaceKey)
at PdfSharp.Fonts.PlatformFontResolver.ResolveTypeface(String familyName, Boolean isBold, Boolean isItalic)
at EmailQueue.AddCopyToEFolder.MyFontResolver.ResolveTypeface(String familyName, Boolean isBold, Boolean isItalic)
at PdfSharp.Fonts.FontFactory.ResolveTypeface(String familyName, FontResolvingOptions fontResolvingOptions, String typefaceKey)
at PdfSharp.Drawing.XGlyphTypeface.GetOrCreateFrom(String familyName, FontResolvingOptions fontResolvingOptions)
at PdfSharp.Drawing.XFont.Initialize()
at MigraDoc.Rendering.FontHandler.FontToXFont(Font font, PdfFontEncoding encoding)
at MigraDoc.Rendering.ParagraphRenderer.get_CurrentFont()
at MigraDoc.Rendering.ParagraphRenderer.InitFormat(Area area, FormatInfo previousFormatInfo)
at MigraDoc.Rendering.ParagraphRenderer.Format(Area area, FormatInfo previousFormatInfo)
at MigraDoc.Rendering.TopDownFormatter.FormatOnAreas(XGraphics gfx, Boolean topLevel)
at MigraDoc.Rendering.FormattedDocument.Format(XGraphics gfx)
at MigraDoc.Rendering.DocumentRenderer.PrepareDocument()
at MigraDoc.Rendering.PdfDocumentRenderer.PrepareDocumentRenderer(Boolean prepareCompletely)
at MigraDoc.Rendering.PdfDocumentRenderer.PrepareRenderPages()
at MigraDoc.Rendering.PdfDocumentRenderer.RenderDocument()
at EmailQueue.AddCopyToEFolder.<Run>d__3.MoveNext()

感谢您提供的任何帮助

Answer 1

看起来您必须对文档中使用的字体使用 IFontResolver 接口(interface)。

很可能您的应用没有访问 Azure 服务器上安装的 TTF 文件的权限，或者未安装所需的 TTF。

另请参阅:
https://forum.pdfsharp.net/viewtopic.php?f=8&t=3244
https://forum.pdfsharp.net/viewtopic.php?f=8&t=3073

编辑:要回答已编辑的问题:您的字体解析器将所有未处理的请求传递给 PlatformFontResolver.ResolveTypeface(familyName, isBold, isItalic); 这显然不适用于 Azure。因此，请将此调用替换为异常，并确保您的代码在本地计算机上运行而不会引发该异常 - 那么它也应该在 Azure 上运行。