Cheap Windows Hosting Review

A Deep Dive into C# Events

Posted on by Pablo Francesco

Events in C# are a way for a class to provide notifications to clients of that class when some interesting thing happens to an object. The most familiar use for events is in graphical user interfaces; typically, the classes that represent controls in the interface have events that are notified when the user does something to the control (for example, click a button).

1. What is an Event?

In C#, an event is a mechanism through which a class (publisher) can notify its consumers (subscribers) of a change or activity. The publisher determines when to trigger the event, and the subscribers determine what action to take in response.

Events are based on the delegate model in C#.

2. How to Use Events?

Here’s a step-by-step guide:

2.1 Declare a delegate

The delegate will define the signature of the event handlers.

public delegate void Notify();  // Delegate declaration

2.2 Declare the event using the delegate

public event Notify ProcessCompleted;  // Event declaration

2.3 Raise the event

protected virtual void OnProcessCompleted()
{
    ProcessCompleted?.Invoke();
}

3. A Simple Example

Here’s an example of how to create and use events:

public class ProcessBusinessLogic
{
    public delegate void ProcessCompletedEventHandler();
    public event ProcessCompletedEventHandler ProcessCompleted;

    public void StartProcess()
    {
        Console.WriteLine("Process Started!");
        // Some processing logic...

        OnProcessCompleted();
    }

    protected virtual void OnProcessCompleted()
    {
        ProcessCompleted?.Invoke();
    }
}

public class MainClass
{
    public static void Main(string[] args)
    {
        ProcessBusinessLogic bl = new ProcessBusinessLogic();
        bl.ProcessCompleted += bl_ProcessCompleted;  // Register with an event
        bl.StartProcess();
    }

    // Event handler
    public static void bl_ProcessCompleted()
    {
        Console.WriteLine("Process Completed!");
    }
}

4. Events with EventArgs

Using EventArgs, you can pass custom information when the event is triggered.

public class ProcessEventArgs : EventArgs
{
    public string Message { get; set; }
}

public class ProcessBusinessLogic
{
    public delegate void ProcessCompletedEventHandler(object sender, ProcessEventArgs e);
    public event ProcessCompletedEventHandler ProcessCompleted;

    public void StartProcess()
    {
        Console.WriteLine("Process Started!");

        OnProcessCompleted(new ProcessEventArgs { Message = "Process Finished!" });
    }

    protected virtual void OnProcessCompleted(ProcessEventArgs e)
    {
        ProcessCompleted?.Invoke(this, e);
    }
}

public class MainClass
{
    public static void Main(string[] args)
    {
        ProcessBusinessLogic bl = new ProcessBusinessLogic();
        bl.ProcessCompleted += bl_ProcessCompleted;
        bl.StartProcess();
    }

    public static void bl_ProcessCompleted(object sender, ProcessEventArgs e)
    {
        Console.WriteLine(e.Message);
    }
}

5. Using EventHandler Delegate

Instead of declaring a custom delegate, C# provides a generic EventHandler delegate, which you can use for most events.

public class ProcessBusinessLogic
{
    public event EventHandler<ProcessEventArgs> ProcessCompleted;

    public void StartProcess()
    {
        Console.WriteLine("Process Started!");

        OnProcessCompleted(new ProcessEventArgs { Message = "Process Done!" });
    }

    protected virtual void OnProcessCompleted(ProcessEventArgs e)
    {
        ProcessCompleted?.Invoke(this, e);
    }
}

6. Anonymous Methods and Lambda Expressions with Events

You can also use anonymous methods or lambda expressions to handle events:

ProcessBusinessLogic bl = new ProcessBusinessLogic();
bl.ProcessCompleted += (sender, e) =>
{
    Console.WriteLine(e.Message);
};
bl.StartProcess();

Events are a fundamental concept in C# (and .NET in general) that facilitate a decoupled design between objects. They allow objects to communicate without needing to reference each other directly. By understanding and effectively using events, developers can create systems that are more modular, maintainable, and scalable.

Recommend ASP.NET Core 7.0.10 Hosting

Feature and reliability are the most important things when choosing a good ASP.NET Core hosting. HostForLIFE is the leading provider of Windows hosting and affordable ASP.NET Core , their servers are optimized for PHP web applications such as the latest ASP.NET Core version. The performance and the uptime of the ASP.NET Core  hosting service are excellent, and the features of the web hosting plan are even greater than what many hosting providers ask you to pay for. At HostForLIFEASP.NET, customers can also experience fast ASP.NET Core hosting. The company invested a lot of money to ensure the best and fastest performance of the datacenters, servers, network and other facilities. Its data centers are equipped with top equipment like cooling system, fire detection, high-speed Internet connection, and so on. That is why HostForLIFEASP.NET guarantees 99.9% uptime for ASP.NET Core . And the engineers do regular maintenance and monitoring works to assure its ASP.NET Core  hosting are security and always up.

hostforlifebanner