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Callback Technology of callback in. net

Source: Internet
Author: User
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At the beginning of. net2.0, a new interface icallbackeventhandler is provided to indicate that the control can be used as the target interface of the server's callback event. The method provided by this interface can also achieve partial page update.
Icallbackeventhandler mainly provides two methods:
(1) string getcallbackresult ();
No parameter. The returned data type is string type, and the returned content is the result of callback event execution.
(2) void raisecallbackevent (string eventargment );
No return value. The parameter type is string type. This parameter is generally used for data parameters transmitted between the client and the server.
If a control requires a local callback function, it must implement the icallbackeventhandler interface. To obtain the results returned by the server getcallbackresult on the client, you must call
Public String getcallbackeventreference (Control, string argument, string clientcallback, string context)
In this method, control indicates the server control that processes the client callback, that is, the control that implements the icallbackeventhandler interface. Argument is the parameter passed from the client to the server method void raisecallbackevent (string eventargment. Clientcallback is handled by the customer service. Program The name of the string returned by the getcallbackresult method processed by the program. Context, the client script calculated on the client before the callback is started, also known as the script context.
Below is a simple example. Code It is very simple, not to mention too much.
(1) client code Code
<% @ Page Language = " C # " Autoeventwireup = " True " Codefile = " Default2.aspx. CS " Inherits = " Default2 "   %>

<!Doctype HTML public "-// W3C // dtd xhtml 1.0 transitional // en" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

< Html Xmlns = "Http://www.w3.org/1999/xhtml" >
< Head Runat = "Server" >
< Title > No title page </ Title >
< Script Type = "Text/JavaScript" >
Function Callbackdo ()
{
VaR Resultstr = Specified parameter Doc ument. getelementbyid ( " Text1 " ). Value;
<% = This . Clientscript. getcallbackeventreference ( This , " Resultstr " , " Getresult " , Null ) %>
}
Function Getresult (datastr)
{
Document. getelementbyid ( " Mytext " ). Innerhtml = Datastr;
}
</ Script >
</ Head >
< Body >
< Form ID = "Form1" Runat = "Server" >
< Div >
< Div >
< Input ID = "Text1" Type = "Text"   /> </ Div >
< Div > < Input ID = "Button1" Type = "Button" Value = "Button" Onclick = "Callbackdo ()" /> </ Div >
< Div ID = "Mytext" > </ Div >
</ Div >
</ Form >
</ Body >
</ Html >

(2) server code Code
Public   Partial   Class Default2: system. Web. UI. Page, icallbackeventhandler
{
String Resultstr =   "" ;
Protected   Void Page_load ( Object Sender, eventargs E)
{

}

Public void raisecallbackevent ( string eventargument)
{< br> resultstr = " after being processed by the server, " + eventargument;
}

Public StringGetcallbackresult ()
{
ReturnResultstr;
}
}

(3) Test Results
Enter "" in the input box, and click the button. The page displays "after being processed by the server"

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Related Keywords:
callback device callback example callback listener callback pattern callback programming c callback define callback

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