Clarify delegation and events

I,Delegated what

A container that can store pointers for methods (method signatures) in a certain format

II,Syntax

Demo1

DGSayHi (Page_Load (DGSayHi dgSayHi = dgSayHi (Response. Write (SayHiSomeWhere (Response. Write (location +}View Code

Custom button: Demo2

MyButton class:

. Click + = MyButton_Click (dgMyClick! = DgMyClick (DateTime. Now );}View Code

Demo2 call:

Page_Load (MyButton m = m. Text = m. dgMyClick = Response. Write (. Format (}View Code

III,Syntactic sugar

In c #, there are many concise syntaxes. The essence is to convert the compiler into the complete syntax during compilation.

Demo3

Page_Load (Button1_Click (DGTest dg = Test1; dg + = Test2; dg + = Test3; dg-= Test3; dg (); Response. write (Response. write (Response. write (}View Code

IV,Delegate

1. After delegation compilation, a class with the same name is claimed, such as DGTest, which inherits from MulticastDelegate and MulticastDelegate inherits from Delegate.

2. The essence of the Delegate append method is to create a new Delegate object for the appended method and store the method pointer to the parent class (Delegate) of the object's parent class) intPrt (a data type dedicated to storing pointers) variable, and then add the newly created Delegate to the array of the current delegate object (dg.

V,Purpose of delegation

1. Delegate when return value demo4

Page_Load (Unnamed1_Click (DGTest dg = InvokeTest (DGTest InvokeTest (Response. Write (}View Code

2. method when the demo5 Parameter

Page_Load (button#click (Response. Write (}View Code

VI,Delegated processing string

Demo6

DGMakeUpStr (Page_Load (MakeUpStr (str + = [] MakeUpStrArr ([] arrstrNew = (I =; I <arrStr. length; I ++ arrstrNew [I] = button#click ([] strArr = [] {, [] strArrNew = (I =; I <strArrNew. length; I ++}View Code

VII,Disadvantages of delegation

Click = null can be used to clear all registered events.

Click can be used to trigger a "fake" event.

Solution: Set the delegate member to private and add AddClickEventHandler and RemoveClickEventHander public methods.

Demo7

Page_Load (MyButton m = m. Text = m. dgMyClick + = Response. Write (. Format (}View Code

Optimization Method:

MyButtonSelf class:

DgMyClick + = dgMyClick-=. Click + = MyButtonSelf_Click (dgMyClick! = DgMyClick (DateTime. Now );}View Code

8,Event

The event mechanism automatically changes the modified delegate variable to private, and provides both the add and remove methods.

The delegated optimized version.

Demo8

MyButtonEvent class:

. Click + = MyButtonSelf_Click (dgMyClick! = DgMyClick (DateTime. Now );}View Code

Call class:

Page_Load (MyButtonEvent m = m. Text = m. dgMyClick + = MyButtonClick; Response. Write (. Format (}View Code

 

 

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