How Do Events and Event Handlers Work in C#?

C# Events and Event Handlers: A Deep Dive

Event-driven programming, especially in UI development, relies heavily on event handling. An event signifies a change of state or occurrence within an object. Event handlers, in turn, are methods triggered by these events, allowing custom code execution in response to specific actions.

Understanding Delegates in C#

To understand event handlers, it's crucial to grasp the concept of delegates. A delegate is a type representing a method; it defines the method's signature (return type and parameter list), essentially acting as a method pointer.

The Importance of Event Handlers

Event handlers are vital because they provide a structured response mechanism to events. They enable targeted code execution upon event occurrence. This separation of event triggering from method execution enhances code maintainability and flexibility.

Building an Event Handler

Creating an event handler involves defining a method that matches the delegate's signature associated with the event. Consider the EventHandler delegate, which accepts two parameters (an object and an EventArgs instance) and returns void. A corresponding event handler would look like this:

<code class="language-csharp">void OnEventOccurred(object sender, EventArgs e)
{
    // Event handling logic here
}</code>

Event Subscription

After creating the handler, subscribe to the event using the = operator, adding the handler to the invocation list:

<code class="language-csharp">eventHandler += new EventHandler(OnEventOccurred);</code>

Event Triggering

To initiate the event and execute subscribed handlers, call the event-raising method. This triggers the execution of all registered handlers:

<code class="language-csharp">eventHandler.OnChanged("Event triggered");</code>

This event-handler mechanism effectively decouples event invocation and method execution, resulting in more maintainable and scalable event-driven applications.

The above is the detailed content of How Do Events and Event Handlers Work in C#?. For more information, please follow other related articles on the PHP Chinese website!