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C# Events (How it Works for Developers)

Events in C# are a fundamental part of event-driven programming. They allow objects to communicate and notify others when something of interest happens. In this guide, we will explore events and how to declare and use them. Let’s break it down step by step to ensure a clear understanding. We'll also explore IronPDF for PDF operations in C# applications.

What Are Events in C#?

Events in C# enable communication between objects. When an event is raised, other objects can respond to it. Events rely on delegates, which act as type-safe pointers to methods. An event delegate type defines the signature of methods that can handle the public event, ensuring consistency in event data handling.

Core Components of Events

To fully understand events, let’s look at their main components:

1. Publisher Class

The publisher class is the source of the event. It is responsible for declaring the event and raising it when a specific action or condition occurs. This process typically involves an event handler method to determine when the event occurs. The publisher also uses an event delegate to define the signature of the methods that can handle the event. For example, in a graphical user interface (GUI), a button control acts as the publisher when it raises a "Click" event.

2. Subscriber Class

The subscriber class listens for events and reacts to them. A subscriber registers its interest in an event by attaching an event handling method to the event. When the publisher raises the event, the subscriber’s event handler method executes. A single event can have multiple subscribers, each responding differently when the event happens.

3. Delegates

Delegates are the foundation of events in C#. They are type-safe pointers to methods and define the contract that all event handlers must follow. Delegates ensure that only methods with a specific signature can handle the event, providing a consistent and error-free event-handling mechanism.

4. Event Handlers

Event handlers are methods in the subscriber class that are executed when an event is triggered. They contain the logic to handle the event, such as updating the UI, logging data, or performing calculations. The signature of an event handler must match the delegate type associated with the event. Additionally, other classes can use event handlers to react to shared events. It makes it easier to implement events in a modular and reusable way.

5. Event Data

In many cases, events need to convey additional information to subscribers. This is achieved using event data classes, which are derived from the base EventArgs class. The event data contains specific details about the event, such as a message, status, or other relevant information.

How to Declare and Use Events in C#

Step 1: Declare a Delegate

Delegates define the method signature for event handlers. In this example, we create a delegate to represent the event handler with two parameters: object sender and EventArgs e.

public delegate void MyEventHandler(object sender, EventArgs e);
public delegate void MyEventHandler(object sender, EventArgs e);
Public Delegate Sub MyEventHandler(ByVal sender As Object, ByVal e As EventArgs)
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Step 2: Declare an Event

Events are declared using the event keyword and are based on the delegate type. Here’s an example:

public class Publisher
{
    public event MyEventHandler Notify; // Declare the event.
}
public class Publisher
{
    public event MyEventHandler Notify; // Declare the event.
}
Public Class Publisher
	Public Event Notify As MyEventHandler ' Declare the event.
End Class
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Step 3: Raise the Event

The event is raised by calling the delegate and passing the necessary parameters.

public void TriggerEvent()
{
    if (Notify != null) // Check if there are subscribers.
    {
        Notify(this, EventArgs.Empty); // Raise the event.
    }
}
public void TriggerEvent()
{
    if (Notify != null) // Check if there are subscribers.
    {
        Notify(this, EventArgs.Empty); // Raise the event.
    }
}
Public Sub TriggerEvent()
	If Notify IsNot Nothing Then ' Check if there are subscribers.
		Notify(Me, EventArgs.Empty) ' Raise the event.
	End If
End Sub
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Step 4: Subscribe to the Event

Subscribers register event handlers using the += operator:

Publisher publisher = new Publisher();
Subscriber subscriber = new Subscriber();
publisher.Notify += subscriber.OnNotify; // Subscribe to the event.
Publisher publisher = new Publisher();
Subscriber subscriber = new Subscriber();
publisher.Notify += subscriber.OnNotify; // Subscribe to the event.
Dim publisher As New Publisher()
Dim subscriber As New Subscriber()
publisher.Notify += subscriber.OnNotify ' Subscribe to the event.
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Step 5: Handle the Event

An event handler is a method in the subscriber class that matches the delegate signature:

public void OnNotify(object sender, EventArgs e)
{
    Console.WriteLine("Event received!");
}
public void OnNotify(object sender, EventArgs e)
{
    Console.WriteLine("Event received!");
}
Public Sub OnNotify(ByVal sender As Object, ByVal e As EventArgs)
	Console.WriteLine("Event received!")
End Sub
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IronPDF: C# PDF Library

IronPDF, a versatile library for working with PDFs in .NET, integrates seamlessly with C# applications. Combined with events in C#, it can provide a dynamic way to handle real-time scenarios like progress updates, error handling or notifications during PDF generation or manipulation. Let’s explore this relationship engagingly. In C#, events are a way to signal that something has happened. They allow one part of your program to notify other parts about specific occurrences, such as a file being processed, a task completed, or an error encountered.

How Does IronPDF Fit?

IronPDF allows you to generate, modify, and secure PDFs, and integrating it with events can make your application more interactive. For instance:

  • Progress Tracking: Notify subscribers about the percentage of completion when generating a large PDF report.
  • Error Handling: Trigger an event if an issue arises during PDF rendering or saving.
  • Custom Actions: Execute custom logic, like logging or UI updates, after specific PDF operations.

Example: Generating a PDF with Event Notifications

Here’s a simple example to demonstrate using IronPDF with events:

using IronPdf;
using System;

// Program class
class Program
{
    // Define a custom event for progress updates
    public static event Action<int> ProgressUpdated;

    public static void Main()
    {
        License.LicenseKey = "License-Key";
        // Subscribe to the ProgressUpdated event
        ProgressUpdated += DisplayProgress;

        Console.WriteLine("Generating PDF...");
        GeneratePdf(); // Generate the PDF
    }

    // Method to generate PDF and trigger progress updates
    static void GeneratePdf()
    {
        try
        {
            var Renderer = new ChromePdfRenderer();
            for (int i = 0; i <= 100; i += 20)
            {
                // Simulate progress
                System.Threading.Thread.Sleep(500);
                ProgressUpdated?.Invoke(i); // Trigger event with progress value
            }
            // Generate a PDF
            var PdfDocument = Renderer.RenderHtmlAsPdf("<h1>Hello, IronPDF with Events!</h1>");
            PdfDocument.SaveAs("IronPDF/example.pdf");
            ProgressUpdated?.Invoke(100); // Final update
            Console.WriteLine("PDF generated successfully!");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Error: {ex.Message}");
        }
    }

    // Event handler to display progress
    static void DisplayProgress(int progress)
    {
        Console.WriteLine($"Progress: {progress}%");
    }
}
using IronPdf;
using System;

// Program class
class Program
{
    // Define a custom event for progress updates
    public static event Action<int> ProgressUpdated;

    public static void Main()
    {
        License.LicenseKey = "License-Key";
        // Subscribe to the ProgressUpdated event
        ProgressUpdated += DisplayProgress;

        Console.WriteLine("Generating PDF...");
        GeneratePdf(); // Generate the PDF
    }

    // Method to generate PDF and trigger progress updates
    static void GeneratePdf()
    {
        try
        {
            var Renderer = new ChromePdfRenderer();
            for (int i = 0; i <= 100; i += 20)
            {
                // Simulate progress
                System.Threading.Thread.Sleep(500);
                ProgressUpdated?.Invoke(i); // Trigger event with progress value
            }
            // Generate a PDF
            var PdfDocument = Renderer.RenderHtmlAsPdf("<h1>Hello, IronPDF with Events!</h1>");
            PdfDocument.SaveAs("IronPDF/example.pdf");
            ProgressUpdated?.Invoke(100); // Final update
            Console.WriteLine("PDF generated successfully!");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Error: {ex.Message}");
        }
    }

    // Event handler to display progress
    static void DisplayProgress(int progress)
    {
        Console.WriteLine($"Progress: {progress}%");
    }
}
Imports IronPdf
Imports System

' Program class
Friend Class Program
	' Define a custom event for progress updates
	Public Shared Event ProgressUpdated As Action(Of Integer)

	Public Shared Sub Main()
		License.LicenseKey = "License-Key"
		' Subscribe to the ProgressUpdated event
		AddHandler Me.ProgressUpdated, AddressOf DisplayProgress

		Console.WriteLine("Generating PDF...")
		GeneratePdf() ' Generate the PDF
	End Sub

	' Method to generate PDF and trigger progress updates
	Private Shared Sub GeneratePdf()
		Try
			Dim Renderer = New ChromePdfRenderer()
			For i As Integer = 0 To 100 Step 20
				' Simulate progress
				System.Threading.Thread.Sleep(500)
				RaiseEvent ProgressUpdated(i)
			Next i
			' Generate a PDF
			Dim PdfDocument = Renderer.RenderHtmlAsPdf("<h1>Hello, IronPDF with Events!</h1>")
			PdfDocument.SaveAs("IronPDF/example.pdf")
			RaiseEvent ProgressUpdated(100)
			Console.WriteLine("PDF generated successfully!")
		Catch ex As Exception
			Console.WriteLine($"Error: {ex.Message}")
		End Try
	End Sub

	' Event handler to display progress
	Private Shared Sub DisplayProgress(ByVal progress As Integer)
		Console.WriteLine($"Progress: {progress}%")
	End Sub
End Class
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C# Events (How it Works for Developers): Figure 1 - Output

Conclusion

C# Events (How it Works for Developers): Figure 2 - Licensing

Events in C# when combined with IronPDF create a powerful system for dynamic PDF generation and management. Events provide a clean, efficient way to handle PDF operations asynchronously, while IronPDF offers robust functionality for PDF creation, editing, and manipulation across .NET platforms. IronPDF offers a free trial to test all features without limitations. Commercial licenses start at $749 and provide access to the complete suite of PDF generation and processing capabilities.

Frequently Asked Questions

How can I implement C# events in my application?

To implement C# events, you need to define a delegate that specifies the signature of the event handler, declare the event using this delegate, raise the event at the appropriate time, and subscribe to the event with a method that matches the delegate signature.

What are the core components of C# events?

The core components of C# events include the publisher, which declares and raises the event; the subscriber, which listens for the event; delegates, which act as type-safe pointers to methods; event handlers, which execute when the event is triggered; and event data, which conveys information about the event to subscribers.

How can a PDF library enhance C# event handling?

A PDF library like IronPDF can enhance C# event handling by allowing you to integrate event-driven notifications into PDF processing tasks. This can include real-time progress updates, error notifications, and the execution of custom logic after certain PDF operations.

How do delegates support event handling in C#?

Delegates in C# support event handling by defining the method signature that event handlers must follow. They ensure that only methods with the correct signature can be used to handle the event, maintaining type safety and consistency.

What role do event handlers play in C# events?

Event handlers are methods that execute in response to an event being raised. They contain the logic needed to handle the event and must conform to the signature defined by the delegate associated with the event.

How can C# events be used for dynamic PDF generation?

C# events can be used for dynamic PDF generation by integrating event-driven notifications into the process. This allows you to track progress, handle errors, and perform custom actions during PDF creation using a library like IronPDF.

What are the steps to raise an event in C#?

To raise an event in C#, you need to first declare the event using a delegate. Then, within the publisher class, you raise the event by invoking it when a specific condition is met. Subscribers that have attached event handlers will execute their respective methods in response.

How do C# events improve PDF processing in .NET applications?

C# events improve PDF processing in .NET applications by enabling asynchronous handling of PDF operations. This allows for real-time updates, error detection, and the invocation of custom logic, making the PDF management process more dynamic and responsive.

Chipego
Software Engineer
Chipego has a natural skill for listening that helps him to comprehend customer issues, and offer intelligent solutions. He joined the Iron Software team in 2023, after studying a Bachelor of Science in Information Technology. IronPDF and IronOCR are the two products Chipego has been focusing on, but his knowledge of ...Read More