How to Generate PDFs with Async and Multithreading

using IronPdf;
using System.Threading.Tasks;

// Instantiate ChromePdfRenderer to create PDF documents from HTML strings.
ChromePdfRenderer renderer = new ChromePdfRenderer();

// Array of HTML strings to be converted into PDF documents.
string[] htmlStrings = { "<h1>Html 1</h1>", "<h1>Html 2</h1>", "<h1>Html 3</h1>" };

// Create an array to store the tasks that will render the HTML strings to PDF.
var renderingTasks = new Task<PdfDocument>[htmlStrings.Length];

// Loop through each HTML string to start a new task for rendering it as a PDF.
for (int i = 0; i < htmlStrings.Length; i++)
{
    int index = i; // Capture the current loop index for use within the asynchronous task.
    renderingTasks[i] = Task.Run(async () =>
    {
        // Asynchronously render the HTML string to a PDF document.
        return await renderer.RenderHtmlAsPdfAsync(htmlStrings[index]);
    });
}

// Uncomment the line below to wait for all rendering tasks to complete.
// Necessary if you are calling this block within an asynchronous method.
// await Task.WhenAll(renderingTasks);

Imports IronPdf

Imports System.Threading.Tasks



' Instantiate ChromePdfRenderer to create PDF documents from HTML strings.

Private renderer As New ChromePdfRenderer()



' Array of HTML strings to be converted into PDF documents.

Private htmlStrings() As String = { "<h1>Html 1</h1>", "<h1>Html 2</h1>", "<h1>Html 3</h1>" }



' Create an array to store the tasks that will render the HTML strings to PDF.

Private renderingTasks = New Task(Of PdfDocument)(htmlStrings.Length - 1){}



' Loop through each HTML string to start a new task for rendering it as a PDF.

For i As Integer = 0 To htmlStrings.Length - 1

	Dim index As Integer = i ' Capture the current loop index for use within the asynchronous task.

	renderingTasks(i) = Task.Run(Async Function()

		' Asynchronously render the HTML string to a PDF document.

		Return Await renderer.RenderHtmlAsPdfAsync(htmlStrings(index))

	End Function)

Next i



' Uncomment the line below to wait for all rendering tasks to complete.

' Necessary if you are calling this block within an asynchronous method.

' await Task.WhenAll(renderingTasks);

using IronPdf;
using System;
using System.Collections.Generic;
using System.Threading.Tasks;

// List of HTML strings to be converted into PDFs.
var htmlQueue = new List<string>() 
{ 
    "<h1>Html 1</h1>", 
    "<h1>Html 2</h1>", 
    "<h1>Html 3</h1>" 
};

// Instantiate the ChromePdfRenderer, which is used for rendering HTML to PDF.
ChromePdfRenderer renderer = new ChromePdfRenderer();

// List for storing the rendered PDF documents.
List<PdfDocument> pdfResults = new List<PdfDocument>();

// Use Parallel.ForEach to convert each HTML string in the list to a PDF document.
Parallel.ForEach(htmlQueue, html =>
{
    // Render HTML to PDF.
    PdfDocument pdf = renderer.RenderHtmlAsPdf(html);

    // Lock the pdfResults list when adding to make it thread-safe.
    lock (pdfResults)
    {
        pdfResults.Add(pdf);
    }
    
    // Optionally, save the PDF document to disk.
    // Uncomment the line below to save each PDF with a unique file name.
    // pdf.SaveAs($"output_{Guid.NewGuid()}.pdf");
});

// Now the pdfResults list contains the PDF documents created from the HTML input.
// Optional: Perform additional operations on the pdfResults list here.

Imports IronPdf

Imports System

Imports System.Collections.Generic

Imports System.Threading.Tasks



' List of HTML strings to be converted into PDFs.

Private htmlQueue = New List(Of String)() From {"<h1>Html 1</h1>", "<h1>Html 2</h1>", "<h1>Html 3</h1>"}



' Instantiate the ChromePdfRenderer, which is used for rendering HTML to PDF.

Private renderer As New ChromePdfRenderer()



' List for storing the rendered PDF documents.

Private pdfResults As New List(Of PdfDocument)()



' Use Parallel.ForEach to convert each HTML string in the list to a PDF document.

Parallel.ForEach(htmlQueue, Sub(html)

	' Render HTML to PDF.

	Dim pdf As PdfDocument = renderer.RenderHtmlAsPdf(html)



	' Lock the pdfResults list when adding to make it thread-safe.

	SyncLock pdfResults

		pdfResults.Add(pdf)

	End SyncLock



	' Optionally, save the PDF document to disk.

	' Uncomment the line below to save each PDF with a unique file name.

	' pdf.SaveAs($"output_{Guid.NewGuid()}.pdf");

End Sub)



' Now the pdfResults list contains the PDF documents created from the HTML input.

' Optional: Perform additional operations on the pdfResults list here.