Windows Phone 7 custom events

In Windows Phone application development, events can be seen everywhere. The system has encapsulated various event mechanisms, such as button-clicking events. In actual development, we need to customize some events for the relevant classes to meet the business requirements, especially when using the observation mode, using events in WP7 is a matter of course.

The steps for custom events are as follows:

1. inherit from the eventargs class to implement Custom Event parameters;

2. Define a delegate;

3. Define an event

4. Add events.

Next, let's take a look at the implementation of a custom event in the demo. This demo is a simple event monitoring call process for the status of network requests:

Custom Event parameter class

Statechangedeventargs. CS

 Using System;

 Namespace Eventdemo
{
 ///   <Summary>  
 ///  Status event
  ///   </Summary>  
      Public   Class Statechangedeventargs: eventargs
{
 Public   Readonly   String Newstate;
 Public   Readonly Datetime timestamp;

 Public Statechangedeventargs ( String Newstate)
{
 This . Newstate = newstate;
 This . Timestamp = datetime. now;
}
}
}

Define events in the business class:

Nettask. CS

 Using System;
 Using System. net;
 Using System. Threading;
 Using System. IO;

Namespace Eventdemo
{
 Public   Class Nettask
{
 //  Define Delegation  
          Public   Delegate   Void Statechanged (nettask sender, statechangedeventargs ARGs );
 //  Define events  
          Public  Event Statechanged onstatechanged;
 //  Incident Status  
          Public   String Nettaskname = "" ;

 ///   <Summary>  
  ///  Network task
  ///   </Summary>  
 ///   <Param name = "url"> </param>  
          Public   Void Startnettask ( String URL)
{
 Bool Success = False ;
 Int Attempt = 0 ;
 While (Attempt < 3 )
{
Asynccallback callback = Null ;
 //  Enable thread wait  
 Manualresetevent webrequestwait = New Manualresetevent ( False );
Uri targeturi = New Uri (URL );
Httpwebrequest request = (httpwebrequest) webrequest. Create (targeturi );
Request. method = " Post  " ;
 If (Callback = Null )
{
Callback = Delegate (Iasyncresult asrequest)
{
 Try 
{
Success = True ;
Webrequestwait. Set ();
 // ......  
 }
 Catch 
{
Onstatechanged ( This , New Statechangedeventargs ( "  Retry  " ));
Webrequestwait. Set ();
}
};
}
Request. begingetrequeststream (callback, request );

 //  Wait until the thread ends  
 Webrequestwait. waitone ();
 If (SUCCESS)
{
 Break ;
}
Attempt ++;
Thread. Sleep ( 1000 );
}
 If (SUCCESS)
{
Onstatechanged ( This , New Statechangedeventargs ( "  Successful  " ));
Thread. Sleep ( 50 );
}
 Else 
{
Onstatechanged ( This , New Statechangedeventargs ("  Failed  " ));
}
}
}
}

A simple test

         <  Grid  X: Name  = "Contentpanel"  Grid. Row  = "1"  Margin  = "12, 0, 12, 0"  > 
 < Button  Content  = "Test network"  Height  = "72"  Horizontalalignment  = "Left"  Margin  = "143,105"  Name  = "Button1"  Verticalalignment  = "TOP"  Width  = "202"  Click = "Button#click"   /> 
 <  Textblock  Height  = "50"  Horizontalalignment  = "Left"  Margin  = "96,270"  Name  = "Textblock1"  Text  = "Network status :"  Verticalalignment  = "TOP" Width  = "126"   /> 
 <  Textblock  Height  = "48"  Horizontalalignment  = "Left"  Margin  = "34,326"  Name  = "Textblock2"  Text  = ""  Verticalalignment = "TOP"  Width  = "377"   /> 
 </  Grid  > 

Mainpage. XAML. CS

 Using System. windows;
 Using Microsoft. Phone. controls;

 Namespace Eventdemo
{
 Public   Partial   Class Mainpage: phoneapplicationpage
{
 Public Mainpage ()
{
Initializecomponent ();
}

 Private   Void Button#click ( Object Sender, routedeventargs E)
{
Nettask = New Nettask ();
Nettask. onstatechanged + = onstatechanged;
Nettask. nettaskname ="  Test Network  " ;
Nettask. startnettask ( "  Http://www.cnblogs.com  " );
}

 Public   Void Onstatechanged ( Object Sender, statechangedeventargs E)
{
Nettask temp = sender As Nettask;
Textblock2.text = temp. nettaskname + "  ,  " + E. newstate + "  ,  " + E. timestamp. tolongtimestring ();
}
}
}

The running result is as follows: