Delegates and Events

Delegate

A class in .NET that encapsulates a method.

Delegate

A reference type data type that holds a reference to a method.

Delegate

A class that can call any method as long as its signature matches.

delegate keyword

The keyword used in declaring a delegate on a class.

Signature

Must match between a delegate and the method it references.

Access modifier

The first item to identify when declaring a delegate.

Return type

The type specified when declaring a delegate, such as void, int, or string.

Delegate name

The desired name specified when declaring a delegate.

Parameters

The parameters specified inside the open and close parentheses of a delegate declaration.

delegate ()

Delegate declaration syntax

Delegate instantiation

The process of creating a delegate instance that refers to a method.

new keyword

The keyword used to instantiate a delegate in the example.

Delegate invocation

The process of invoking a referenced method through a delegate.

Referenced method

The method that a delegate references.

Parameters of a delegate

The parameters that should have the same count as the referenced method when referencing it.

Generic delegates

Delegates that are not bound to any specific type.

Generic delegate

A delegate that can reference a method that returns and takes parameters of different types.

Type parameter

The type represented by X in the generic delegate example.

Delegates and interfaces

Both include the declaration, but they have differences.

Delegates

They have no implementation; they are just safe callbacks and only have a declaration.

Interfaces

A class that implements this can implement all the methods associated with it.

Delegates

They can reference any method of a class that provides arguments and return types.

Interfaces

This allows extending some of the objects’ functionality.

Delegates

They are used if a class needs more than one implementation of the method.

Interfaces

They can implement a method only once.

Delegates

They are faster to execute but slower to get.

Interfaces

They are slower in executing but faster to get.

Event handling

In C#.NET, events are usually task initiators.

Event

This is a member of a class that is fired whenever a specific action takes place.

Event

This occurs when a specific action takes place.

Event handler

The method that is created and registered to an event and is automatically invoked when the event occurs.

Event handler

The methods that are invoked when an event occurs.

Method registration

This is done through delegates that specify the signature of a method registered for it.

Event declaration

Before declaring an event, a delegate to which the event is supposed to be associated should be declared first.

Event-associated delegate

The delegate to which an event is supposed to be associated.

Delegate in the event declaration

The delegate that contains two parameters and can reference methods that have the same count of parameters.

Parameter count

It can reference a method with the same count of parameters.

Event declaration

What is the next step after declaring the delegate?

public event delegate_name event_name

Event declaration syntax.

event keyword

The keyword used when declaring an event.

Event name

The preferred name given to an event when declaring it.

Delegate name

This is used in the event declaration.

Adding a delegate to an event

The process of registering a delegate with an event using the += operator.

+= operator

The operator used to add a delegate to an event.

Event subscription

The registration of a new subscription to an event.

event_name += delegate_instance

Event subscription syntax.

Event accessors

The two methods automatically generated by the compiler when the += operator is used with an event.

add accessor An event accessor used to register a new subscription to an event.

remove accessor An event accessor used to unregister the subscription to an event.

Property accessors The get and set accessors used with properties.

Event accessors

The add and remove accessors that are similar to the get and set accessors used with properties.

Unregistering a subscription

The process performed by using the remove accessor.

Registering a subscription

The process performed by using the add accessor.

add and remove

The two event accessors generated by the compiler.

Event accessor code

The code that can be used in add and remove to check some conditions before registering or unregistering the subscriber.

Subscriber

The method or delegate registered or unregistered through an event's add or remove accessor.