Do events have return type

In .NET, events are a language feature designed to enable communication and notification between objects. Unlike methods or functions, events do not have return types because they are not meant to provide a result or return a value.

The primary purpose of an event is to provide a mechanism for one object (the event publisher or sender) to notify other objects (the event subscribers or listeners) that a certain action or state change has occurred. Events are typically used to facilitate the observer pattern, where multiple subscribers can register to receive notifications when an event is raised.

Absence of return types

The absence of return types in events stems from their nature as a means of broadcasting information rather than requesting or returning data. Events are based on a publish-subscribe model, where the publisher raises an event and all subscribed listeners are notified. The focus is on the one-way flow of information from the publisher to the subscribers.

Here's an example to illustrate the concept of events without return types in C#:

public class Publisher { public event EventHandler<EventArgs> MyEvent; public void DoSomething() { // Perform some actions... // Raise the event OnMyEvent(); } protected virtual void OnMyEvent() { // Check if there are subscribers to the event if (MyEvent != null) { // Raise the event MyEvent(this, EventArgs.Empty); } } } public class Subscriber { public Subscriber(Publisher publisher) { // Subscribe to the event publisher.MyEvent += HandleMyEvent; } private void HandleMyEvent(object sender, EventArgs e) { // Handle the event notification Console.WriteLine("Event received!"); } }

In this example, the Publisher class defines an event named MyEvent, which is of type EventHandler<EventArgs>. The Publisher raises the event by invoking the OnMyEvent method. The Subscriber class registers to listen to the MyEvent event by subscribing to it using the += operator.

When the Publisher raises the event, all subscribed instances of Subscriber will receive the event notification and execute the event handler method HandleMyEvent. Note that the event handler does not return any value; it simply performs some action based on the event notification.


Events in .NET do not have return types because their purpose is to facilitate one-way communication, broadcasting notifications to subscribers rather than returning values or results.