C# Event Handler（開発者向けの仕組み）

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(Of 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(html As String, outputPath As String)
            _worker.RunWorkerAsync(Tuple.Create(html, outputPath))
        End Sub

        ' Perform PDF generation in background
        Private Sub OnDoWork(sender As Object, e As DoWorkEventArgs)
            Dim args = DirectCast(e.Argument, Tuple(Of String, String))
            Dim html = args.Item1
            Dim path = args.Item2
            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(sender As Object, 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
    Module Program

        Sub Main(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 Sub OnPdfGenerated(sender As Object, e As PdfGeneratedEventArgs)
            Console.WriteLine($"PDF generated at: {e.FilePath}")
        End Sub
    End Module

End Namespace