C# Events and Delegates

C# events and delegates are powerful tools that enable developers to create dynamic and responsive applications. Events facilitate communication between different components, while delegates act as function pointers, allowing for indirect method invocation. Together, these features enhance code modularity, flexibility, and maintainability.

Event handling is a fundamental concept in C#, allowing classes to respond to events raised by other classes. The process involves three key components: the event sender, the event handler, and the event itself. When an event occurs, the sender triggers it, and any registered event handlers respond accordingly.

Example:

// Declare the event based on the delegate
public event VideoEventHandler VideoEnded;

public void Play()
{
// Simulate video playback
Console.WriteLine(“Playing video…”);

// When the video ends, raise the event
OnVideoEnded();
}

protected virtual void OnVideoEnded()
{
// Raise the event
VideoEnded?.Invoke(this, EventArgs.Empty);
}
}

public class NotificationService
{
public void SendNotification(object sender, EventArgs e)
{
Console.WriteLine(“Sending notification: Video has ended.”);
}
}

In this example, the VideoPlayer class raises the VideoEnded event when the video playback ends. The NotificationService class registers an event handler to respond to this event.

C# empowers developers to create custom events and delegates tailored to specific needs. This customization allows for the design of event-driven systems that precisely fit the application requirements.

Example:

public event StockPriceChangedEventHandler StockPriceChanged;

public void UpdateStockPrice(string stockSymbol, decimal newPrice)
{
// Update the stock price and raise the event
OnStockPriceChanged(new StockPriceChangedEventArgs(stockSymbol, newPrice));
}

protected virtual void OnStockPriceChanged(StockPriceChangedEventArgs e)
{
StockPriceChanged?.Invoke(this, e);
}
}

public class StockPriceChangedEventArgs : EventArgs
{
public string StockSymbol { get; }
public decimal NewPrice { get; }

public StockPriceChangedEventArgs(string stockSymbol, decimal newPrice)
{
StockSymbol = stockSymbol;
NewPrice = newPrice;
}
}

In this example, the StockMarket class raises a custom StockPriceChanged event whenever the stock price is updated. The StockPriceChangedEventArgs class holds relevant data about the stock symbol and the new price.