how to pass html as a string using wkhtmltopdf?

STDIn and STDOut have been redirected in this example, so you shouldn't need files at all.

public static class Printer
{
    public const string HtmlToPdfExePath = "wkhtmltopdf.exe";

    public static bool GeneratePdf(string commandLocation, StreamReader html, Stream pdf, Size pageSize)
    {
        Process p;
        StreamWriter stdin;
        ProcessStartInfo psi = new ProcessStartInfo();

        psi.FileName = Path.Combine(commandLocation, HtmlToPdfExePath);
        psi.WorkingDirectory = Path.GetDirectoryName(psi.FileName);

        // run the conversion utility
        psi.UseShellExecute = false;
        psi.CreateNoWindow = true;
        psi.RedirectStandardInput = true;
        psi.RedirectStandardOutput = true;
        psi.RedirectStandardError = true;

        // note: that we tell wkhtmltopdf to be quiet and not run scripts
        psi.Arguments = "-q -n --disable-smart-shrinking " + (pageSize.IsEmpty? "" : "--page-width " + pageSize.Width +  "mm --page-height " + pageSize.Height + "mm") + " - -";

        p = Process.Start(psi);

        try {
            stdin = p.StandardInput;
            stdin.AutoFlush = true;
            stdin.Write(html.ReadToEnd());
            stdin.Dispose();

            CopyStream(p.StandardOutput.BaseStream, pdf);
            p.StandardOutput.Close();
            pdf.Position = 0;

            p.WaitForExit(10000);

            return true;
        } catch {
            return false;

        } finally {
            p.Dispose();
        }
    }

    public static void CopyStream(Stream input, Stream output)
    {
        byte[] buffer = new byte[32768];
        int read;
        while ((read = input.Read(buffer, 0, buffer.Length)) > 0) {
            output.Write(buffer, 0, read);
        }
    }
}

Redirecting STDIN is probably the easiest way to accomplish what you're trying to do.

One method of redirecting STDIN with wkhtmltopdf (in ASP.Net) is as follows:

    private void WritePDF(string HTML)
    {
        string inFileName,
                outFileName,
                tempPath;
        Process p;
        System.IO.StreamWriter stdin;
        ProcessStartInfo psi = new ProcessStartInfo();

        tempPath = Request.PhysicalApplicationPath + "temp\\";
        inFileName = Session.SessionID + ".htm";
        outFileName = Session.SessionID + ".pdf";

        // run the conversion utility
        psi.UseShellExecute = false;
        psi.FileName = "c:\\Program Files (x86)\\wkhtmltopdf\\wkhtmltopdf.exe";
        psi.CreateNoWindow = true;
        psi.RedirectStandardInput = true;
        psi.RedirectStandardOutput = true;
        psi.RedirectStandardError = true;

        // note that we tell wkhtmltopdf to be quiet and not run scripts
        // NOTE: I couldn't figure out a way to get both stdin and stdout redirected so we have to write to a file and then clean up afterwards
        psi.Arguments = "-q -n - " + tempPath + outFileName;

        p = Process.Start(psi);

        try
        {
            stdin = p.StandardInput;
            stdin.AutoFlush = true;

            stdin.Write(HTML);
            stdin.Close();

            if (p.WaitForExit(15000))
            {
                // NOTE: the application hangs when we use WriteFile (due to the Delete below?); this works
                Response.BinaryWrite(System.IO.File.ReadAllBytes(tempPath + outFileName));
                //Response.WriteFile(tempPath + outFileName);
            }
        }
        finally
        {
            p.Close();
            p.Dispose();
        }

        // delete the pdf
        System.IO.File.Delete(tempPath + outFileName);
    }

Note that the code above assumes that there's a temp directory available in your application directory. Also, you must explicitly enable write access to that directory for the user account used when running the IIS process.

I know this is an older post, but I want future developers to have this option. I had the same need, and the idea of having to start a background process just to get a PDF inside of a web app is terrible.

Here's another option: https://github.com/TimothyKhouri/WkHtmlToXDotNet

It's a .NET native wrapper around wkhtmltopdf.

Sample code here:

var pdfData = HtmlToXConverter.ConvertToPdf("<h1>COOOL!</h1>");

Note, it's not thread-safe as of right now - I'm working on that. So just use a monitor or something or a lock.