Custom event arguments in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of creating custom event arguments in C#?

Custom event arguments allow you to pass additional data with an event, beyond the standard EventArgs, so event handlers can receive specific information related to the event.

beginner

How do you define a custom event argument class in C#?

You create a class that inherits from EventArgs and add properties to hold the extra data you want to pass with the event.

intermediate

Why should custom event argument classes inherit from EventArgs?

Inheriting from EventArgs follows .NET conventions and allows your custom arguments to be used with standard event patterns and delegates like EventHandler<T>.

beginner

What is the typical signature of an event handler using custom event arguments?

The event handler method usually has two parameters: an object sender and a custom event argument type derived from EventArgs, e.g., void Handler(object sender, MyEventArgs e).

intermediate

How do you raise an event with custom event arguments in C#?

You create an instance of your custom event argument class with the needed data, then call the event delegate passing 'this' as sender and the custom args instance.

What base class should a custom event argument class inherit from?

A Object

B EventArgs

C EventHandler

D Delegate

Custom event argument classes should inherit from EventArgs to follow .NET event pattern conventions.

Which of the following is the correct event handler signature for a custom event argument MyEventArgs?

A void Handler(MyEventArgs e, object sender)

B void Handler(object sender)

C void Handler(object sender, MyEventArgs e)

D void Handler()

The standard signature is (object sender, MyEventArgs e) where sender is the event source and e holds event data.

Why create custom event arguments instead of using EventArgs directly?

A To avoid using delegates

B To make events slower

C To prevent event subscription

D To pass extra information with the event

Custom event arguments let you send extra data to event handlers, which EventArgs alone cannot do.

How do you raise an event with custom arguments in C#?

A Call the event delegate with sender and new custom args instance

B Call the event delegate with only sender

C Call the event delegate with no parameters

D Call the event delegate with only custom args

You pass both the sender (usually 'this') and an instance of your custom event args to the event delegate.

Which keyword is used to declare an event in C#?

A event

B delegate

C class

D void

The 'event' keyword declares an event in C#.

Explain how to create and use custom event arguments in C#.

Think about how to pass extra information with events.

Describe the benefits of using custom event arguments instead of the default EventArgs.

Consider what extra information event handlers might need.