Software--c#--grammer_delegate--event

2018-05-01 10:49:47

A delegate is a type, and an event is a member of a class or struct, as in a field, property. Must be declared in a class or struct.

Extended-Observe Viewer mode Publish/subscribe Publish-Subscribe mode

A basic form

1. Declare the delegate, build the event in the class, and trigger the code as shown

1 usingSystem;2 usingSystem.Collections.Generic;3 usingSystem.Linq;4 usingSystem.Text;5 usingSystem.Threading.Tasks;6 7 namespaceEventdemo8 {9     //Event 1 of 5 elements--Deletegate declareTen     Delegate voidHandler (); One  A     //Publisher -     //1. Event Declare -     //2. Fire event code the     classIncrementer -     {         -          Public EventHandler eventpub;//Create Event -          +         //code that triggers the event -          Public voiddoincrement () +         { A              for(inti =0; I < -; i++) at             { -                 ifI A==0&& eventpub! =NULL) - eventpub (); -             } -         } -  in     } -}

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2. Create event handlers and register events in subscribers.

1 usingSystem;2 usingSystem.Collections.Generic;3 usingSystem.Linq;4 usingSystem.Text;5 usingSystem.Threading.Tasks;6 7 namespaceEventdemo8 {9     /*Ten * Subscribers One * 1. Event handlers A * 2. Inject Publisher into the constructor and construct the code to add a handler method to the event. Subscribe to events.  -      */ -     classSubscribecode the     { -          Public intDozonecount {Get;Private Set; } -  -         //Event Handlers +         voidIncrementcount () -         { +dozonecount++; A         } at  -         //Constructor Subscription Event -          PublicSubscribecode (Incrementer Inc) -         { -Dozonecount =0; -Inc.eventpub + =Incrementcount; in         } -  to     } +}

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Two EventHandler

Public vodi EventHandler (Object sender, EventArgs e)

(this, null) to match a consistent

Three custom EventArgs derived classes are required to transfer data.

1. First define the class of the derived child EventArgs

1 usingSystem;2 usingSystem.Collections.Generic;3 usingSystem.Linq;4 usingSystem.Text;5 usingSystem.Threading.Tasks;6 7 namespaceEventdemo.customerdefine8 {9     /*Public void EventHandler (Object sender, EventArgs e)Ten * EventArgs is designed to not pass any parameters, One * You need to declare a class derived from EventArgs and customize the fields that hold the data.  A      *  - * Naming specification ends with args -      */ the      Public classCustomereventargs:eventargs -     { -          Public intDestinatedata {Get;Set; } -     } +}

custom EventArgs Derived classes

2. The remaining steps are as follows, note that when you define an event handler

1) The return value is void.

2) Publisher

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3) Subscribe

1 usingSystem;2 usingSystem.Collections.Generic;3 usingSystem.Linq;4 usingSystem.Text;5 usingSystem.Threading.Tasks;6 7 namespaceEventdemo.customerdefine8 {9     classSubscribeclassTen     { One          Public intTransferData {Get;Set; } A  -          Public voidAccountmethod (Object send, Customereventargs e) -         { theConsole.WriteLine ("{0} transfer data,/t {1} send", - E.destinatedata, send. ToString ()); -transferdata++; -         } +          Publicsubscribeclass (publisherclass pc) -         { +TransferData =0; APc.handler + =Accountmethod; at         } -     } -}

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Note The Remove event handler is removed from the last look for the first match, similar to the delegate's method

Advanced usage, Event accessors

Change + = = To. Let the event execute any custom code that we want.

Two accessors Add remove

Declaring an event accessor is similar to declaring a property that returns void

Public event EventHandler Countedadozen

{

Add

{ ... } Execute + = operator

Remove

{ ... } Execute-= operator

}

After the declaration, the event does not contain any inline delegate objects. You must implement your own mechanism for storing and removing time registration methods.

Software--c#--grammer_delegate--event