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  • Direct flow depending on incoming dynamic type

    - by Improfane
    I have a listener class that accepts GUI change events in one method. The incoming event objects have a superclass of a type of GUI Event, the behaviour should depend on the dynamic type of the incoming variable. I wanted to do do lots of methods like: handleGUIEvent(EventChangedX event) handleGUIEvent(EventChangedY event) I am using a single event listener and receiving objects of various types but the behaviour should be different for each. What would you do? I do not want to use a switch statement as this would get unmaintainable.

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  • try .. catch blocks - when to use

    - by Konrad
    I have always been of the belief that if a method can throw an exception then it is reckless not to protect this call with a meaningful try block. I just posted 'You should ALWAYS wrap calls that can throw in try, catch blocks.' to this question and was told that it was 'remarkably bad advice' - I'd like to understand why. Thanks!

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  • handling broadcast reciver

    - by rayman
    Hi, I have an app which has MainActivity(without gui.. please just flow with it:) ) now this MainActivity running a service, this service using sendBroadcast() in order to comunnicate with the MainActivity.. now ofcourse i need to registerReceiver in the onResume() of the MainActivity. but i also need to add unregisterReceiver(receiver) in the onDestroy() of the MainActivity. problem is: when i first start that app i need it to up the service, and i dont want the user to lose focus, so i press finish() after i`am starting the service.. but then auto invoked also unregisterReceiver(receiver).. and this is not good for me.. i get error it's said it couldnt find any registerd reciver. so i fixed it by delete this line.. but i am sure its going to 'revenege' me in the future, when/where could i have problem if i wont use unregisterReceiver(receiver).. at the onDestroy() thanks, ray.

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  • Handling RSS Tags with NSXMLParser for iPhone

    - by MartinW
    I've found the following code for parsing through RSS but it does not seem to allow for nested elements: - (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName{ NSLog(@"ended element: %@", elementName); if ([elementName isEqualToString:@"item"]) { // save values to an item, then store that item into the array... [item setObject:currentTitle forKey:@"title"]; [item setObject:currentLink forKey:@"link"]; [item setObject:currentSummary forKey:@"summary"]; [item setObject:currentDate forKey:@"date"]; [item setObject:currentImage forKey:@"media:thumbnail"]; The RSS to used is: <item><title>Knife robberies and burglaries up</title> <description>The number of robberies carried out at knife-point has increased sharply and burglaries are also up, latest crime figures indicate</description> <link>http://news.bbc.co.uk/go/rss/-/1/hi/uk/7844455.stm</link> <guid isPermaLink="false">http://news.bbc.co.uk/1/hi/uk/7844455.stm</guid> <pubDate>Thu, 22 Jan 2009 13:02:03 GMT</pubDate><category>UK</category> <media:thumbnail width="66" height="49" url="http://newsimg.bbc.co.uk/media/images/45400000/jpg/_45400861_policegeneric_pa.jpg"/> </item> I need to extract the "url" element from the "media" tag. Thanks Martin

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  • Suppress "Done, but with errors on page" in IE

    - by calebthorne
    I have a website using lots of jQuery and JavaScript that produces a "Done, but with errors on page" message in the footer of IE. Everything on the site works perfectly, so I don't want to spend the time troubleshooting the exact error. All I would like to do is suppress the "Done, but with errors on page" message so that clients don't freak out. I tried the following at the top of the page with no success: window.onerror = function() {return true;}

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  • WP7 - Cancelling ContextMenu click event propagation

    - by Praetorian
    I'm having a problem when the Silverlight toolkit's ContextMenu is clicked while it is over a UIElement that has registered a Tap event GestureListener. The context menu click propagates to the underlying element and fires its tap event. For instance, say I have a ListBox and each ListBoxItem within it has registered both a ContextMenu and a Tap GestureListener. Assume that clicking context menu item2 is supposed to take you to Page1.xaml, while tapping on any of ListBox items themselves is supposed to take you to Page2.xaml. If I open the context menu on item1 in the ListBox, then context menu item2 is on top of ListBox item2. When I click on context menu item2 I get weird behavior where the app navigates to Page1.xaml and then immediately to Page2.xaml because the click event also triggered the Tap gesture for ListBox item2. I've verified in the debugger that it is always the context menu that receives the click event first. How do I cancel the context menu item click's routed event propagation so it doesn't reach ListBox item2? Thanks for your help!

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  • C - What is the proper format to allow a function to show an error was encountered?

    - by BrainSteel
    I have a question about what a function should do if the arguments to said function don't line up quite right, through no fault of the function call. Since that sentence doesn't make much sense, I'll offer my current issue. To keep it simple, here is the most relevant and basic function I have. float getYValueAt(float x, PHYS_Line line, unsigned short* error) *error = 0; if(x < line.start.x || x > line.end.x){ *error = 1; return -1; } if(line.slope.value != 0){ //line's equation: y - line.start.y = line.slope.value(x - line.start.x) return line.slope.value * (x - line.start.x) + line.start.y; } else if(line.slope.denom == 0){ if(line.start.x == x) return line.start.y; else{ *error = 1; return -1; } } else if(line.slope.num == 0){ return line.start.y; } } The function attempts to find the point on a line, given a certain x value. However, under some circumstances, this may not be possible. For example, on the line x = 3, if 5 is passed as a value, we would have a problem. Another problem arises if the chosen x value is not within the interval the line is on. For this, I included the error pointer. Given this format, a function call could work as follows: void foo(PHYS_Line some_line){ unsigned short error = 0; float y = getYValueAt(5, some_line, &error); if(error) fooey(); else do_something_with_y(y); } My question pertains to the error. Note that the value returned is allowed to be negative. Returning -1 does not ensure that an error has occurred. I know that it is sometimes preferred to use the following method to track an error: float* getYValueAt(float x, PHYS_Line line); and then return NULL if an error occurs, but I believe this requires dynamic memory allocation, which seems even less sightly than the solution I was using. So, what is standard practice for an error occurring?

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  • Socket select() Handling Abrupt Disconnections

    - by Genesis
    I am currently trying to fix a bug in a proxy server I have written relating to the socket select() call. I am using the Poco C++ libraries (using SocketReactor) and the issue is actually in the Poco code which may be a bug but I have yet to receive any confirmation of this from them. What is happening is whenever a connection abruptly terminates the socket select() call is returning immediately which is what I believe it is meant to do? Anyway, it returns all of the disconnected sockets within the readable set of file descriptors but the problem is that an exception "Socket is not connected" is thrown when Poco tries to fire the onReadable event handler which is where I would be putting the code to deal with this. Given that the exception is silently caught and the onReadable event is never fired, the select() call keeps returning immediately resulting in an infinite loop in the SocketReactor. I was considering modifying the Poco code so that rather than catching the exception silently it fires a new event called onDisconnected or something like that so that a cleanup can be performed. My question is, are there any elegant ways of determining whether a socket has closed abnormally using select() calls? I was thinking of using the exception message to determine when this has occured but this seems dirty to me.

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  • Is it possible to call the main(String[] args) after catching an exception?

    - by Jason
    I'm working on a Serpinski triangle program that asks the user for the levels of triangles to draw. In the interests of idiot-proofing my program, I put this in: Scanner input= new Scanner(System.in); System.out.println(msg); try { level= input.nextInt(); } catch (Exception e) { System.out.print(warning); //restart main method } Is it possible, if the user punches in a letter or symbol, to restart the main method after the exception has been caught?

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  • Handling of data truncation (short reads/writes) in FUSE

    - by Vi
    I expect any good program should do all their reads and writes in a loop until all data written/read without relying that write will write everything (even with regular files). Am I right? Implemented simple FUSE filesystem which only allows reading and writing with small buffers, very often returning that it is written less bytes that in a buffer (using -o direct_io). Some programs work, some not (notably mountlo). Are them buggy or programs should not expect truncated writes and reads from the regular files? In general, are seekable file descriptors expected to truncate data like sockets and pipes?

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  • Set reference = null in finally block?

    - by deamon
    A colleague of mine sets reference to null in finally blocks. I think this is nonsense. public Something getSomething() { JDBCConnection jdbc=null; try { jdbc=JDBCManager.getConnection(JDBCTypes.MYSQL); } finally { JDBCManager.free(jdbc); jdbc=null; // <-- Useful or not? } } What do you think of it?

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  • C# Dynamic Keyword exception handling

    - by user972255
    The below code throws an exception when executing this line (i.e. something.Add(name)). I want to catch the actual exception when executing this. I mean I don't want to use catch(Exception ex) instead of that I want to know what is the correct exception thrown here. try { dynamic name= "test"; var something = new List<decimal>(); something.Add(name); } catch(Exception ex) { throw ex; } Thanks in advance.

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  • How to differentiate between exceptions i can show the user, and ones i can't?

    - by Ian Boyd
    i have some business logic that traps some logically invalid situations, e.g. trying to reverse a transaction that was already reversed. In this case the correct action is to inform the user: Transaction already reversed or Cannot reverse a reversing transaction or You do not have permission to reverse transactions or This transaction is on a session that has already been closed or This transaction is too old to be reversed The question is, how do i communicate these exceptional cases back to the calling code, so they can show the user? Do i create a separate exception for each case: catch (ETransactionAlreadyReversedException) MessageBox.Show('Transaction already reversed') catch (EReversingAReversingTransactionException) MessageBox.Show('Cannot reverse a reversing transaction') catch (ENoPermissionToReverseTranasctionException) MessageBox.Show('You do not have permission to reverse transactions') catch (ECannotReverseTransactionOnAlredyClosedSessionException) MessageBox.Show('This transaction is on a session that has already been closed') catch (ECannotReverseTooOldTransactionException) MessageBox.Show('This transaction is too old to be reversed') Downside for this is that when there's a new logical case to show the user: Tranasctions created by NSL cannot be reversed i don't simply show the user a message, and instead it leaks out as an unhandled excpetion, when really it should be handled with another MessageBox. The alternative is to create a single exception class: `EReverseTransactionException` With the understanding that any exception of this type is a logical check, that should be handled with a message box: catch (EReverseTransactionException) But it's still understood that any other exceptions, ones that involve, for example, an memory ECC parity error, continue unhandled. In other words, i don't convert all errors that can be thrown by the ReverseTransaction() method into EReverseTransactionException, only ones that are logically invalid cause of the user.

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  • Freetype2 (error-)return value documentation

    - by Awaki
    In short, I'm looking for documentation that would limit the error situations to check for after a Freetype library function failed, much like the OpenGL and Win32 APIs document the error codes generated by their respective functions. I can't seem to find such documentation though, so I was wondering how to best handle translation of Freetype errors to typed exceptions. Background: I am currently in the process of implementing font-rendering capability (using Freetype) for my GUI framework, which makes strong use of typed exceptions to indicate error situations. However, the Freetype docs seem to completely omit what errors can be expected from what functions. That, if such documentation does indeed not exist, would basically leave me with two options: either guessing which errors make sense for a certain Freetype function (obviously prone to mistakes on my part), or considering every error code for translation into appropriate exceptions (less verbose since I would have to write the translation only once). Performance isn't really critical in the code that calls the Freetype library, so even the latter option would probably be acceptable, but surely there must be some kind of documentation on which library calls may return what Freetype error? Is there any such documentation which I just somehow managed to not find? Should I go the route of generically expecting every error code for translation? Or are there other ways to approach this problem? By the way, I wanted to avoid introducing some kind of generic FreetypeException (containing a description of the Freetype error) since I intended to completely hide what libraries I'm using (not from a legal point-of-view, mind you), but I guess I can be convinced to do this anyway if the consensus is that it would be the best option. I don't think it matters for this question, but I'm writing in C++.

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  • Exporting to CSV with dynamic field type handling

    - by serhio
    I have to do an export from DB to CSV. field; fileld; field... etc Have 3 types of fields: Alpha, Numeric and Bool respresented as "alphaValue",intValue and True/False. I try to encapsulate this in a fields collection, in order to export if alpha then set "", if Bool=True/False if numeric let as is. and try to build a CsvField class: Public Structure?Class CsvField(Of T As ???) End Structure Enum FieldType Alpha Bool Numeric End Enum any suggestions welcomed.

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  • How should I handle the case in which a username is already in use?

    - by idealmachine
    I'm a JavaScript programmer and new to PHP and MySQL (want to get into server-side coding). Because I'm trying to learn PHP by building a simple online game (more specifically, correspondence chess), I'm starting by implementing a simple user accounts system. Of course, user registration comes first. What are the best practices for: How I should handle the (likely) possibility that when a user tries to register, the username he has chosen is already in use, particularly when it comes to function return values?($result === true is rather ugly, and I'm not sure whether checking the MySQL error code is the best way to do it either) How to cleanly handle varying page titles?($gPageTitle = '...'; require_once 'bgsheader.php'; is also rather ugly) Anything else I'm doing wrong? In some ways, PHP is rather different from JavaScript... Here is a (rather large) excerpt of the code I have written so far. Note that this is a work in progress and is missing security checks that I will add as my next step. function addUser( $username, $password ) { global $gDB, $gPasswordSalt; $stmt = $gDB->prepare( 'INSERT INTO user(user_name, user_password, user_registration) VALUES(?, ?, NOW())' ); $stmt || trigger_error( 'Failed to prepare statement: ' . htmlspecialchars( $gDB->error ) ); $hashedPassword = hash_hmac( 'sha256', $password, $gPasswordSalt, true ); $stmt->bind_param( 'ss', $username, $hashedPassword ); if( $stmt->execute() ) { return true; } elseif( $stmt->errno == 1062) { return 'exists'; } else { trigger_error( 'Failed to execute statement: ' . htmlspecialchars( $stmt->error ) ); } } $username = $_REQUEST['username']; $password = $_REQUEST['password']; $result = addUser( $username, $password ); if( $result === true ) { $gPageTitle = 'Registration successful'; require_once 'bgsheader.php'; echo '<p>You have successfully registered as ' . htmlspecialchars( $username ) . ' on this site.</p>'; } elseif( $result == 'exists' ) { $gPageTitle = 'Username already taken'; require_once 'bgsheader.php'; echo '<p>Someone is already using the username you have chosen. Please try using another one instead.'; } else { trigger_error('This should never happen'); } require_once 'bgsfooter.php';

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  • WPF Event Handler in Another Class

    - by Nathan Tornquist
    I have built a series of event handlers for some custom WPF controls. The event handles format the text displayed when the user enters or leaves a textbox based on the type of data contained (Phone number, zip code, monetary value, etc.) Right now I have all of the events locally in the C# code directly attached to the xaml. Because I have developed a could controls, this means that the logic is repeated a lot, and if I want to change the program-wide functionality I would have to make changes everywhere the event code is located. I am sure there is a way to put all of my event handlers in a single class. Can anyone help point me in the correct direction? I saw this article: Event Handler located in different class than MainWindow But I'm not sure if it directly relates to what I'm doing. I would rather make small changes to the existing logic that I have, as it works, then rewrite everything into commands. I would essentially like to something like this if possible: LostFocus="ExpandedTextBoxEvents.TextBox_LostFocus" It is easy enough to do something like this: private void TextBoxCurrencyGotFocus(object sender, RoutedEventArgs e) { ExpandedTextBoxEvents.TextBoxCurrencyGotFocus(sender, e); } private void TextBoxCurrencyLostFocus(object sender, RoutedEventArgs e) { ExpandedTextBoxEvents.TextBoxCurrencyLostFocus(sender, e); } But that is less elegant.

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  • Handling Denormalized Schema with Eclipselink

    - by iamrohitbanga
    Hello All I have a denormalized table containing employee information. The fields are employee id, name and department name. The primary key is a composite one consisting of all three fields. An employee can belong to multiple departments. I want to read/write the objects in the table using the Eclipselink Dynamic Persistence API (which is infact a wrapper on top of JPA descriptors etc.). Example Data: 1 e1 dep1 2 e1 dep2 3 e2 dep1 4 e2 dep3 5 e3 dep1 5 e3 dep2 5 e3 dep3 A normal ReadAllQuery (select query) on the table returns a DynamicEntity corresponding to each row in the table. However I want to club all entities based on the emp id and return all the departments he belongs to as a list. I can merge the entities after retrieving them but if I can use some Eclipselink feature out of the box then it would be better. One way to do the read is the following: I create two dynamic types corresponding to employee: Having id,name as the primary key Having id, department as the primary key, I create a OneToManyMapping from the first type to the second one. Then when I query the first type it does return the departments to which employee belongs as a list of DynamicEntity of the second type. This satisfies the read scenario. Is there a better way of doing this? Is this inherently supported by Eclipselink or JPA? I cannot get the same dynamic type configuration working for the write scenario. This is because when I write the changes using the writeObject method of UnitOfWork, it generates insert queries which enter the following entries in the table id name department 102 emp_102 102 st 102 dep_102 102 dep_102 102 dep_102 instead of: id name department 102 emp_102 st 102 emp_102 dep_102 102 emp_102 dep_102 102 emp_102 dep_102 Is there any way I can get write to work with this schema using eclipselink? I want to avoid doing the heavy lifting of merging the rows for such a denormalized schema or generating each row before doing a write. Is there no clean way of doing this using Eclipselink or JPA? Thanks in Advance.

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  • How to get the name of the method that caused the exception

    - by SKumar
    My code looks as below. try { _productRepo.GetAllProductCategories(); } catch (Exception ex) { //Do Something } I need a way to show the method name, suppose in the above case if any exception is thrown in the GetAllProductCategories() method, I need to get this method name i.e. "GetAllProductCategories()" as my result. Can any one suggest me how to do this?

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  • Distinguishing between failure and end of file in read loop

    - by celtschk
    The idiomatic loop to read from an istream is while (thestream >> value) { // do something with value } Now this loop has one problem: It will not distinguish if the loop terminated due to end of file, or due to an error. For example, take the following test program: #include <iostream> #include <sstream> void readbools(std::istream& is) { bool b; while (is >> b) { std::cout << (b ? "T" : "F"); } std::cout << " - " << is.good() << is.eof() << is.fail() << is.bad() << "\n"; } void testread(std::string s) { std::istringstream is(s); is >> std::boolalpha; readbools(is); } int main() { testread("true false"); testread("true false tr"); } The first call to testread contains two valid bools, and therefore is not an error. The second call ends with a third, incomplete bool, and therefore is an error. Nevertheless, the behaviour of both is the same. In the first case, reading the boolean value fails because there is none, while in the second case it fails because it is incomplete, and in both cases EOF is hit. Indeed, the program above outputs twice the same line: TF - 0110 TF - 0110 To solve this problem, I thought of the following solution: while (thestream >> std::ws && !thestream.eof() && thestream >> value) { // do something with value } The idea is to detect regular EOF before actually trying to extract the value. Because there might be whitespace at the end of the file (which would not be an error, but cause read of the last item to not hit EOF), I first discard any whitespace (which cannot fail) and then test for EOF. Only if I'm not at the end of file, I try to read the value. For my example program, it indeed seems to work, and I get TF - 0100 TF - 0110 So in the first case (correct input), fail() returns false. Now my question: Is this solution guaranteed to work, or was I just (un-)lucky that it happened to give the desired result? Also: Is there a simpler (or, if my solution is wrong, a correct) way to get the desired result?

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  • Confirmation before closing

    - by saeed
    Hi I am using c# .net windows form application. I have a combo box and a text box and a close window button. Now If I make any change in the combo box or textbox and click on the close window button, it should prompt the user to save the modifications.. If no modification are made ( The user will just run the application, doesnt make any modification) then it should not prompt the user. It should close directly.. How can I do this?

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  • Mapping the System.Exception with FaultException

    - by user357342
    I have used exception sheilding feature of application block, to map System.Exception with class that is marked as DataContract. It works very well. But When I have mapped the System.Exception with FaultException, I got the below error message. "An error has occurred while consuming this service. Please contact your administrator for more information. Error ID: fe2d28b5-8d26-430e-baf4-fe4b39da853c" Please let me know whether I can map the System.Exception with FaultException

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  • In Asp.net i'm not able to catch any exception properly?

    - by Anand
    In Asp.net (c#),i'm not able to catch exception(FileNotFoundException) properly... i don't know the reason..Actually File s not there..But catch statement fails to catch the exception.. here is the code.. try { System.Drawing.Image imgg1 = System.Drawing.Image.FromFile(Server.MapPath("").ToString() + "\\images\\img1.jpg"); } catch (FileNotFoundException) { Response.Write("<script>alert('Please Select and upload Student's Photo');</script>"); }

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  • How to solve Only Web services with a [ScriptService] attribute on the class definition can be called from script

    - by NevenHuynh
    I attempt to use webservice return POCO class generated from entity data model as JSON when using Jquery AJAX call method in webservice. but I have problem with error "Only Web services with a [ScriptService] attribute on the class definition can be called from script", and getting stuck in it, Here is my code : namespace CarCareCenter.Web.Admin.Services { /// <summary> /// Summary description for About /// </summary> [WebService(Namespace = "http://tempuri.org/")] [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] [System.ComponentModel.ToolboxItem(false)] // To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. // [System.Web.Script.Services.ScriptService] public class About : System.Web.Services.WebService { [ScriptMethod(ResponseFormat = ResponseFormat.Json)] [WebMethod] public static Entities.Category getAbout() { Entities.Category about = new Entities.Category(); using (var context = new CarCareCenterDataEntities()) { about = (from c in context.Categories where c.Type == "About" select c).SingleOrDefault(); } return about; } } } aspx page : <script type="text/javascript"> $(document).ready(function () { $.ajax({ type: 'POST', dataType: 'json', contentType: 'application/json; charset=utf-8', url: '/Services/About.asmx/getAbout', data: '{}', success: function (response) { var aboutContent = response.d; alert(aboutContent); $('#title-en').val(aboutContent.Name); $('#title-vn').val(aboutContent.NameVn); $('#content-en').val(aboutContent.Description); $('#content-vn').val(aboutContent.DescriptionVn); $('#id').val(aboutContent.CategoryId); }, failure: function (message) { alert(message); }, error: function (result) { alert(result); } }); $('#SaveChange').bind('click', function () { updateAbout(); return false; }); $('#Reset').bind('click', function () { getAbout(); return false; }) }); function updateAbout() { var abt = { "CategoryId": $('#id').val(), "Name": $('#title-en').val(), "NameVn": $('#title-vn').val(), "Description": $('#content-en').val(), "DescriptionVn": $('#content-vn').val() }; $.ajax({ type: "POST", url: "AboutManagement.aspx/updateAbout", data: JSON.stringify(abt), contentType: "application/json; charset=utf-8", dataType: "json", success: function (response) { var aboutContent = response.d; $('#title-en').val(aboutContent.Name); $('#title-vn').val(aboutContent.NameVn); $('#content-en').val(aboutContent.Description); $('#content-vn').val(aboutContent.DescriptionVn); }, failure: function (message) { alert(message); }, error: function (result) { alert(result); } }); } </script> Do any approaches to solve it ? Please help me . Thanks

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