PageMethods In ASP.NET AJAX
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by Suresh Kumar Goudampally
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CallBack Methods and Their Significance

We can pass parameters to Page methods and then the call back methods. We can pass the references to the four call back methods to call when the page method returns. The four call back methods are

·         onSucceed

·         onError

As we discussed we need to have callback function for success page method call and for unsuccessful page method call. Unsuccessful page method call means if there is an   internal server error on the page.

Using the call back method we can fetch the required result from the page and use it on the client script as required.

//CallBack method when the page call succeeds
function onSucceed(results, currentContext, methodName)
{
      alert(results);
}
 
//CallBack method when the page call fails due to interna, server error
function onError(results, currentContext, methodName)
{
      alert(results);
}

The method names and parameter names are user defined.  We can use any name for the callback methods and their parameters.

The OnSucceed parameter indicates the javascript function to be called when the call has succeeded and the result parameter has the result stored in it in our case the string returned from the code behind file.
The OnError parameter indicates the javascript function to be called when error occurs. The success call back method has three parameters:

·         Result – Returns the output of the page method.

·         currentContext – This is used to handle different logic when single callback is used for multiple page method requests. We can also pass array of values as userContext parameter.

·         methodName – This parameter returns the name of  page method called.

 The error call back method has three parameters:

·         Result – Returns the output of the page method.

·         currentContext – This is used to handle different logic when single callback is used for multiple page method requests. We can also pass array of values as userContext parameter.

·         methodName – This parameter returns the name of  page method called.

The result here return the type of the error, stacktrace, message and type of the exceptions. You can display the required information to the end user using the following   methods of error object

get_exceptionType()
get_mesage()
get_stackTrace()
get_statusCode()
get_timedOut()
 
function onError(result)
{
      alert(result.get_message());
}             

Sending the userContext parameter

var contextArray = "u1";     
PageMethods.GetStatus("p1","p2",onSucceed, onError,contextArray);  

And this can be used on the call back to execute different logic

function onSucceed(result,userContext,methodname)
{ 
      if (userContext = “u1”)
      {
            alert(result);
      }
}

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User Comments

Title: zhe   
Name: li
Date: 2012-12-18 8:10:18 PM
Comment:
test how
Title: akakakak   
Name: pusing
Date: 2012-12-05 11:40:34 PM
Comment:
buseeeeeeeeeeeee
Title: wqeqw   
Name: dasdas
Date: 2012-12-05 2:59:03 AM
Comment:
sdasdasd
Title: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaassssssssssssssssssssssssssssssssssddddddddddddddddddddddddddddddddddddddddddxxxxxxxxxxxxxxxxxxxxxxx   
Name: wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwdddddddddddddddddddddddddddddddaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
Date: 2012-11-28 4:18:36 AM
Comment:
asdddddddddddddddddddddddddcas testing#1
Title: thx   
Name: thx
Date: 2012-11-28 4:16:33 AM
Comment:
thx
Title: aaa   
Name: sss
Date: 2012-11-19 7:25:12 AM
Comment:
fff
Title: سيش   
Name: سشي
Date: 2012-10-23 8:31:23 AM
Comment:
سيش
Title: Mr.   
Name: Farooque
Date: 2012-10-19 10:05:08 AM
Comment:
sfsdf
Title: u   
Name: hgj
Date: 2012-10-17 7:36:06 AM
Comment:
ghjhg
Title: ddd   
Name: dd
Date: 2012-10-16 6:29:48 AM
Comment:
ddd
Title: hefrhfb   
Name: dfnejdfklndg
Date: 2012-09-04 2:59:42 AM
Comment:
fnfjrklmnfensxf
Title: zz   
Name: zz
Date: 2012-08-30 9:53:06 AM
Comment:
zzz
Title: tttyu   
Name: fdfdghf
Date: 2012-08-11 8:41:57 AM
Comment:
ghtjhk,l.k/l;l
Title: dgfdsg   
Name: dsgdsg
Date: 2012-07-26 2:00:31 AM
Comment:
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Title: rty   
Name: rty
Date: 2012-07-19 7:36:48 PM
Comment:
rty
Title: wwt   
Name: kevin
Date: 2012-06-09 12:21:15 AM
Comment:
dfaklj
Title: ds   
Name: ds
Date: 2012-06-06 3:15:53 PM
Comment:
sds
Title: bmbnnnnmbnm   
Name: nbmbnm
Date: 2012-05-18 6:07:18 AM
Comment:
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Title: Excellent   
Name: Srinivasa Rao D
Date: 2011-12-23 1:05:20 AM
Comment:
U save my day..!
Title: Invalid Method Name   
Name: Prakash
Date: 2011-07-08 4:53:41 AM
Comment:
Please change method name as GetPageMethod instead of GetStatus(). Those who are copying this code, that code wont run. check befor every one run. Thanks.
Title: Good One   
Name: sachin
Date: 2011-02-01 7:43:14 AM
Comment:
Understandable for those who are beginner for PageMethods....
Title: Nice Article   
Name: HPR
Date: 2011-01-24 8:41:55 PM
Comment:
Nice informative article.
Title: aa   
Name: aaa
Date: 2011-01-18 5:34:27 AM
Comment:
very nice
Title: why does not work in firefox and safai while javascript is enable?   
Name: AKM
Date: 2010-11-26 7:02:35 AM
Comment:
Work in IE but,why does not work in firefox and safari while javascript is enable on both browser?
Title: Feedback   
Name: Atul Tiwari
Date: 2010-11-22 5:37:58 AM
Comment:
Too good....
Title: A question..   
Name: Dario
Date: 2010-11-14 9:16:49 AM
Comment:
Is it possible for the page method to return a structure instead a simple string?
And how to read it on client side?
Thank you!
Title: Not clear yet   
Name: M
Date: 2010-08-10 6:27:42 AM
Comment:
The article could be better structured. It's all a bit chaotic and confusing...
Title: clear now   
Name: Babak Sekandari
Date: 2010-04-29 9:58:30 AM
Comment:
OK, I understand now.
public static string GetStatus(string s1, string s2){ . . . appears later.
It's better to view the whole article at once.
Very good explanations by the way. Thank you very much.
Title: confused   
Name: Babak Sekandari
Date: 2010-04-28 6:59:47 PM
Comment:
The page method call is: PageMethods.GetStatus(onSucceed, onError);
But the code behind sample is public static string GetPageMethod()

As Woho stated, I don't understand why one is GetPageMethod() and the other is GetStatus()
Title: setting control value   
Name: suresh kumar
Date: 2010-03-26 12:08:31 AM
Comment:
that would be a logical error, have you tried to debug onsucceed method and check the value before it is assigned to textbox. Can you send me the code?
Title: setting control value   
Name: Maulik
Date: 2010-03-25 9:14:31 PM
Comment:
Hi,

OnSucceed event, I want to set the result value to a textbox. For that, I find the textbox and assign result to textbox's "value" property. I receive the expected value for result but textbox has an empty value..any reason?? I use onblur event of another textbox and do the same thing and at that time textbox shows result value..any idea??
Title: Good   
Name: NNN
Date: 2010-03-22 3:19:51 AM
Comment:
Very good article.
Title: GetStatus   
Name: Suresh Kumar
Date: 2010-03-10 4:07:24 AM
Comment:
i am referring to sample method GetStatus in the article.
Title: Interesting, but a bit confusing   
Name: Woho
Date: 2010-03-10 2:33:07 AM
Comment:
You keep referring to the method GetStatus, but I guess you really mean GetPageMethod? Otherwise it doesn't make any sense...
Interesting article although, but feels a bit like "ugly coding" (the concept, not your code :) ).
Title: Good one   
Name: Bijith K B
Date: 2010-03-09 2:04:48 PM
Comment:
Nice article.






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