F# – PDF fun with Markdown and FSharp.Formatting

Yan Cui

I help clients go faster for less using serverless technologies.

I spent the last couple of nights putting together a simple Markdown to PDF formatter using Tomas Petricek’s FSharp.Formatting project and the PdfSharp-MigraDoc library.

To use this library, you can either grab the source from the GitHub repository or get it from Nuget using the following command:

F# Usage

To use the library from F#, you can use the Markdown type defined in the FSharp.Markdown namespace (from the FSharp.Formating library), once you’ve opened the FSharp.Markdown.Pdf namespace you’ll have access to two static extension methods:

• TransformPdf – accepts a string as input and outputs the resulting PDF to a local file path or to a specified Stream.
• WritePdf – accepts a MarkdownDocument generated by the Markdown.Parse method, and outputs the resulting PDF to a local file path or to a specified Stream.

	open FSharp.Markdown
	open FSharp.Markdown.Pdf
	let text = """Some text in Markdown format..."""
	// formatting to PDF and save result to file
	Markdown.TransformPdf(text, @"C:\temp\markdown.pdf")
	// formatting to PDF and save result to stream
	use stream = File.OpenWrite(@"C:\temp\markdown2.pdf")
	Markdown.TransformPdf(text, stream)
	let parsed = Markdown.Parse(text)
	// taking a tokenized Markdown document and formatting to PDF
	// before saving result to file
	Markdown.WritePdf(parsed, @"C:\temp\markdown3.pdf")
	// taking a tokenized Markdown document and formatting to PDF
	// before saving result to stream
	use stream' = File.OpenWrite(@"C:\temp\markdown4.pdf")
	Markdown.WritePdf(parsed, stream')

view raw gistfile1.fs hosted with by GitHub

C# Usage

You can also use this library from C#, however, the static extension methods mentioned above is not accessible in C# because type extensions defined in F# are compiled differently to standard extension methods you find in C# (with far more possibilities I might add, such as extension properties, and static methods, for instance!) and is not recognized by the C# compiler..

You can still access the same functionalities using a MarkdownPdf type, with two static methods:

• Transform – equivalent to Markdown.TransformPdf.
• Write – equivalent to Markdown.WritePdf.

	using FSharp.Markdown;
	using FSharp.Markdown.Pdf;
	var text = "Some text in Markdown format...";
	// formatting to PDF and save result to file
	MarkdownPdf.Transform(text, @"C:\temp\markdown.pdf");
	// formatting to PDF and save result to stream
	using (var stream = File.OpenWrite(@"C:\temp\markdown2.pdf"))
	{
	MarkdownPdf.Transform(text, stream);
	}
	var parsed = Markdown.Parse(text);
	// taking a tokenized Markdown document and formatting to PDF
	// before saving result to file
	MarkdownPdf.Write(parsed, @"C:\temp\markdown3.pdf");
	// taking a tokenized Markdown document and formatting to PDF
	// before saving result to stream
	using (var stream2 = File.OpenWrite(@"C:\temp\markdown4.pdf"))
	{
	MarkdownPdf.Write(parsed, stream2);
	}

view raw gistfile1.txt hosted with by GitHub

You can see an example output here with the corresponding Markdown here.