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Chapte r10 - Delegate, Events and Lambdas pdf
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Chapte r10 - Delegate, Events and Lambdas pdf

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Mô tả chi tiết

Chapter 10.

Delegates,Events, and Lambdas

Hoang Anh Viet

[email protected]

HaNoi University of Technology

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Microsoft Microsoft

Objectives

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“The purpose of Chapter 10 is to demystify the delegate type.

Simply put, a .NET delegate is an object that “points” to other

methods in your application. Using this pattern, you are able to

build systems that allow multiple objects to engage in a two-way

onversation. After you have examined the use of .NET delegates,

you will then be introduced to the C# event keyword, which is

used to implify the manipulation of raw delegate programming.

You wrap up by investigating the role of the C# 2008 lambda

operator (=>) and exploring the connection between delegates,

anonymous methods, and lambda expressions.”

Microsoft Microsoft

Roadmap

10.1 Understanding the .NET Delegate Type

10.2 Defining a Delegate in C#

10.3 The System.MulticastDelegate and System.Delegate

Base class.

10.4 The Simplest Possible Delegate Example

10.5 Retrofiting the Car Type with Delegates

10.6 A more Elaborate Delegate Example

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Microsoft Microsoft

Roadmap

10.7 Understanding Delegate Covarance

10.8 Greating Generic Delegates

10.9 Understanding C# Events.

10.10 The Generic C# EventHandler<T> Delegate.

10.11 Understanding C# Anonymouns Methods

10.12 Understanding Method Group Conversions

10.13 The C# 2008 Lambdas Operator.

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10.1 Understanding the .NET Delegate

Type

 A delegate is a type that references a method.

 Once a delegate is assigned a method, it behaves exactly

like that method .

 The delegate method can be invoked like any other

method, with parameters and a return value.

 Such as :

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public delegate int PerformCalculation(int x, int y);

Microsoft Microsoft

Kinds of Methods

 Any method from any accessible class or struct that

matches the delegate's signature, which consists of the

return type and parameters, can be assigned to the

delegate .

 The method can be either static or an instance method .

 Note :

• In the context of method overloading:

 The signature of a method does not include the

return value.

• In the context of delegates:

 The signature does include the return value.

Microsoft Microsoft

Delegates Overview

 Delegates have the following properties:

• Delegates are like C++ function pointers but are type

safe.

• Delegates allow methods to be passed as

parameters.

• Delegates can be used to define callback methods.

• Delegates can be chained together; for example,

multiple methods can be called on a single event.

• Methods do not have to match the delegate signature

exactly

• Allow code blocks to be passed as parameters in

place of a separately defined method.

Microsoft Microsoft

Efficency of Delegates

 Plug new code into existing classes.

 Makes it possible to programmatically change method

calls.

 Defines callback methods. Allows for an algorithm to be

written in a more general way.

Microsoft Microsoft

Roadmap

10.1 Understanding the .NET Delegate Type

10.2 Defining a Delegate in C#

10.3 The System.MulticastDelegate and System.Delegate

Base class.

10.4 The Simplest Possible Delegate Example

10.5 Retrofiting the Car Type with Delegates

10.6 A more Elaborate Delegate Example

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