问MigraDoc PDF渲染器遇到System.NullReferenceException

EN

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()

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

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;
        }
    }

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()