C# Event Handler (How it Works for Developers)

public event EventHandler PdfGenerationStarted;
public event EventHandler<PdfGeneratedEventArgs> PdfGenerationCompleted;

Public Event PdfGenerationStarted As EventHandler
Public Event PdfGenerationCompleted As EventHandler(Of PdfGeneratedEventArgs)

using System;
using System.ComponentModel;
using IronPdf;
namespace IronPdfEventHandlerExample
{
    // 1. Define custom EventArgs to carry event data
    public class PdfGeneratedEventArgs : EventArgs
    {
        public string FilePath { get; set; }
    }
    // 2. Main class with event, BackgroundWorker, and logic
    public class PdfGenerator
    {
        // Declare the public event using EventHandler<T>
        public event EventHandler<PdfGeneratedEventArgs> PdfGenerated;
        private readonly BackgroundWorker _worker;
        public PdfGenerator()
        {
            _worker = new BackgroundWorker();
            _worker.DoWork += OnDoWork;
            _worker.RunWorkerCompleted += OnRunWorkerCompleted;
        }
        // Start the async operation
        public void GenerateAsync(string html, string outputPath)
        {
            _worker.RunWorkerAsync(new Tuple<string, string>(html, outputPath));
        }
        // Perform PDF generation in background
        private void OnDoWork(object sender, DoWorkEventArgs e)
        {
            var (html, path) = (Tuple<string, string>)e.Argument;
            var renderer = new HtmlToPdf();
            var pdf = renderer.RenderHtmlAsPdf(html);
            pdf.SaveAs(path);
            e.Result = path;
        }
        // Notify subscribers when the PDF is ready
        private void OnRunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            var path = e.Result as string;
            PdfGenerated?.Invoke(this, new PdfGeneratedEventArgs { FilePath = path });
        }
    }
    // 3. Program to wire it all together
    class Program
    {
        public static void Main(string[] args)
        {
            var generator = new PdfGenerator();
            // Subscribe to the PdfGenerated event
            generator.PdfGenerated += OnPdfGenerated;
            Console.WriteLine("Generating PDF asynchronously...");
            generator.GenerateAsync("<h1>Hello, IronPDF!</h1>", "output.pdf");
            Console.WriteLine("Press any key to exit after generation.");
            Console.ReadKey();
        }
        // Event handler for when the PDF is ready
        static void OnPdfGenerated(object sender, PdfGeneratedEventArgs e)
        {
            Console.WriteLine($"PDF generated at: {e.FilePath}");
        }
    }
}

Imports System
Imports System.ComponentModel
Imports IronPdf
Namespace IronPdfEventHandlerExample
	' 1. Define custom EventArgs to carry event data
	Public Class PdfGeneratedEventArgs
		Inherits EventArgs

		Public Property FilePath() As String
	End Class
	' 2. Main class with event, BackgroundWorker, and logic
	Public Class PdfGenerator
		' Declare the public event using EventHandler<T>
		Public Event PdfGenerated As EventHandler(Of PdfGeneratedEventArgs)
		Private ReadOnly _worker As BackgroundWorker
		Public Sub New()
			_worker = New BackgroundWorker()
			AddHandler _worker.DoWork, AddressOf OnDoWork
			AddHandler _worker.RunWorkerCompleted, AddressOf OnRunWorkerCompleted
		End Sub
		' Start the async operation
		Public Sub GenerateAsync(ByVal html As String, ByVal outputPath As String)
			_worker.RunWorkerAsync(New Tuple(Of String, String)(html, outputPath))
		End Sub
		' Perform PDF generation in background
		Private Sub OnDoWork(ByVal sender As Object, ByVal e As DoWorkEventArgs)
'INSTANT VB TODO TASK: VB has no equivalent to C# deconstruction declarations:
			var(html, path) = (Tuple(Of String, String))e.Argument
			Dim renderer = New HtmlToPdf()
			Dim pdf = renderer.RenderHtmlAsPdf(html)
			pdf.SaveAs(path)
			e.Result = path
		End Sub
		' Notify subscribers when the PDF is ready
		Private Sub OnRunWorkerCompleted(ByVal sender As Object, ByVal e As RunWorkerCompletedEventArgs)
			Dim path = TryCast(e.Result, String)
			RaiseEvent PdfGenerated(Me, New PdfGeneratedEventArgs With {.FilePath = path})
		End Sub
	End Class
	' 3. Program to wire it all together
	Friend Class Program
		Public Shared Sub Main(ByVal args() As String)
			Dim generator = New PdfGenerator()
			' Subscribe to the PdfGenerated event
			AddHandler generator.PdfGenerated, AddressOf OnPdfGenerated
			Console.WriteLine("Generating PDF asynchronously...")
			generator.GenerateAsync("<h1>Hello, IronPDF!</h1>", "output.pdf")
			Console.WriteLine("Press any key to exit after generation.")
			Console.ReadKey()
		End Sub
		' Event handler for when the PDF is ready
		Private Shared Sub OnPdfGenerated(ByVal sender As Object, ByVal e As PdfGeneratedEventArgs)
			Console.WriteLine($"PDF generated at: {e.FilePath}")
		End Sub
	End Class
End Namespace