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• Has form post behavior changed in modern browsers? (or How are double clicks handled by the browser)

  - by Alex Czarto

  Background: We are in the process of writing a registration/payment page, and our philosophy was to code all validation and error checking on the server side first, and then add client side validation as a second step (un-obstructive jQuery). We wanted to disable double clicks server side, so we wrote some locking, thread-safe code to handle simultaneous posts/race conditions. When we tried to test this, we realized that we could not cause a simultaneous post or race condition to occur. I thought that (in older browsers anyway) double clicking a submit button worked as follows: User double clicks submit button. Browser sends a post on the first click On the second click, browser cancels/ignores initial post, and initiates a second post (before the first post has returned with a response). Browser waits for second post to return, ignoring initial post response. I thought that from the server side it looked like this: Server gets two simultaneous post requests, executes and responds to them both (unaware that no one is listening to the first response). From our testing (FireFox 3.0, IE 8.0) this is what actually happens: User double clicks submit button Browser sends a post for the first click Browser queues up second click, but waits for the response from the first click. Response returns from first click (response is ignored?). Browser sends a post for the second click. So from a server side: Server receives a single post which it executes and responds to. Then, server receives a second request wich it executes and responds to. My question is, has this always worked this way (and I'm losing my mind)? Or is this a new feature in modern browsers that prevents simultaneous posts to be sent to the server? It seems that for server side double click prevention, we don't have to worry about simultaneous posts or race conditions. Only need to worry about queued up posts. Thanks in advance for any feedback / comments. Alex

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• How do I use the information about exceptions a method throws in .NET in my code?

  - by dotnetdev

  For many methods in .NET, the exceptions they can potentially throw can be as many as 7-8 (one or two methods in XmlDocument, Load() being one I think, can throw this many exceptions). Does this mean I have to write 8 catch blocks to catch all of these exceptions (it is best practise to catch an exception with a specific exception block and not just a general catch block of type Exception). How do I use this information? Thanks

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• Is there a way to catch Fatal error in PHP?

  - by Josef Sábl

  I have this line of PHP code: thisFunctionDoesNotExist(); And it stops script execution with: Fatal error: Call to undefined function I tried using set_error_handler and it does help for warning type of errors. But not for fatal errors. As I understand it from various threads on internet it should be possible to handle by set_error_handler, but I cannot make it work. Can you please post working example?

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• help with exception handling in linq

  - by stackoverflowuser

  I have the following code to retrieve customer name, total (orders ), sum (order details) for reach customer in Northwind database. The problem with below code is that it raises an exception since a few customers dont have any entry in orders table. I know using the query syntax (join) the exception can be avoided. I want to know if the same can be handled with the extension method syntax. CustomerOrderDataContext db = new CustomerOrderDataContext(); var customerOrders = db.Customers.Select(c => new { CompanyName = c.CompanyName, TotalOrders = c.Orders.Count(), TotalQuantity = c.Orders.SelectMany(o => o.Order_Details).Sum(o=>o.Quantity) });

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• Using ManualResetEvent to wait for multiple Image.ImageOpened events

  - by umlgorithm

  Dictionary<Image, ManualResetEvent> waitHandleMap = new Dictionary<Image, ManualResetEvent>(); List<Image> images = GetImagesWhichAreAlreadyInVisualTree(); foreach (var image in images) { image.Source = new BitmapImage(new Uri("some_valid_image_url")); waitHandleMap.Add(image, new ManualResetEvent(false)); image.ImageOpened += delegate { waitHandleMap[image].Set(); }; image.ImageFailed += delegate { waitHandleMap[image].Set(); }; } WaitHandle.WaitAll(waitHandleMap.Values.ToArray()); WaitHandle.WaitAll blocks the current UI thread, so ImageOpened/ImageFailed events would never get fired. Could you suggest me an easy workaround to wait for the multiple ui events?

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• Assign delegate event handler from dynamically added child control

  - by mickyjtwin

  I have a control that handles commenting. In this control, I have set a delegate event handler for sending an email. I then have various types of controls, e.g. blog, articles etc, each of which may or may not have the commenting control added (which is done dynamically with me not knowing the id's), i.e. the commenting control is added outside this control. Each of these controls handles it's emailing differently(hence the event). What I'm trying to determine, is how to assign the event in the parent control. At the moment, I'm having to recursively search through all the controls on the page until I find the comment control, and set it that way. Example below explains: COMMENTING CONTROL public delegate void Commenting_OnSendEmail(); public partial class Commenting : UserControl { public Commenting_OnSendEmail OnComment_SendEmail(); private void Page_Load(object sender, EventArgs e) { if(OnComment_SendEmail != null) { OnComment_SendEmail(); } } } PARENT CONTROL public partial class Blog : UserControl { private void Page_Load(object sender, EventArgs e) { Commenting comControl = (Commenting)this.FindControl<Commenting>(this); if(comControl != null) { comCtrol.OnComment_SendEmail += new Commenting_OnSendMail(Blog_Comment_OnSendEmail); } } } Is there an easier way?

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• Cannot write the output to a text file in cpp program

  - by swapedoc

  I have this input file "https://code.google.com/codejam/contest/351101/dashboard/do/A-large-practice.in?cmd=GetInputFile&problem=374101&input_id=1&filename=A-large-practice.in&redownload_last=1&agent=website&csrfmiddlewaretoken=OWMxNTVmMTUyODBiYjhhN2Q2OTM3ZGJiMTNhNDkwMDF8fDEzNzIxNzI1NTE3ODAzMjA%3D" I tried to read this file :-using freopen("filename.txt",r,stdin); and then I wanted the output written to be written to another text file which I can upload in this codejam practice question for the judge. #include<iostream> #include<cstdio> using namespace std; int main() { int t,k=0,a[2000]; freopen("ab.txt","r",stdin); scanf("%d",&t); while(t--) { freopen("cb.txt","w",stdout); int c; scanf("%d",&c); int n; scanf("%d",&n); for(int i=0;i<n;i++) scanf("%d",&a[i]); printf("Case #%d: ",++k); for(int i=0;i<n-1;i++) {for(int j=i+1;j<n;j++) if((a[i]+a[j])==c) {printf("%d %d\n",i+1,j+1); i=n;} } } return 0; } This is my code. Now the problem is the output file cb.txt contains only the last line of the input. I want the the whole of the output to be written to cb.txt,so what should I do.

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• Keep Hibernate Initializer from Crashing Program

  - by manyxcxi

  I have a Java program using a basic Hibernate session factory. I had an issue with a hibernate hbm.xml mapping file and it crashed my program even though I had the getSessionFactory() call in a try catch try { session = SessionFactoryUtil.getSessionFactory().openStatelessSession(); session.beginTransaction(); rh = getRunHistoryEntry(session); if(rh == null) { throw new Exception("No run history information found in the database for run id " + runId_ + "!"); } } catch(Exception ex) { logger.error("Error initializing hibernate"); } It still manages to break out of this try/catch and crash the main thread. How do I keep it from doing this? The main issue is I have a bunch of cleanup commands that NEED to be run before the main thread shuts down and need to be able to guarantee that even after a failure it still cleans up and goes down somewhat gracefully. The session factory looks like this: public class SessionFactoryUtil { private static final SessionFactory sessionFactory; static { try { // Create the SessionFactory from hibernate.cfg.xml sessionFactory = new Configuration().configure().buildSessionFactory(); } catch (Throwable ex) { // Make sure you log the exception, as it might be swallowed System.err.println("Initial SessionFactory creation failed." + ex); throw new ExceptionInInitializerError(ex); } } public static SessionFactory getSessionFactory() { try { return sessionFactory; } catch(Exception ex) { return null; } } }

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• Rails3 UJS example with unobtrusive dry flash error

  - by user142913

  Hi to everybody thislink text is a demo "done right" about rails3 and UJS, but if you add: validates :name, :presence = true to the Task model that error(500 Internal Server Error) is displayed nowhere. Do you know a correct and clean way to handle it?

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• java checked exception in a catch clause compilation error

  - by srandpersonia

  Hi, I was expecting an compilation error in the following program because of the throw statement in the catch block as IOException is a checked exception and it is not caught by another try block within the catch block. But I am getting "Hurray!" printed. Any explanation would be much appreciated. According to JLS 11.2.3, http://java.sun.com/docs/books/jls/third_edition/html/exceptions.html It is a compile-time error if a method or constructor body can throw some exception type E when both of the following hold: * E is a checked exception type * E is not a subtype of some type declared in the throws clause of the method or constructor. import java.io.*; public class Test{ public static void main(String args[]) { System.out.println(method()); } public static int method() { try{ throw new Exception(); } catch(Exception e){ throw new IOException(); //No compile time error } finally{ System.out.println("Hurray!"); } } } Thanks in advance.

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• How can I process a form's events in another class in VB.NET?

  - by CowKingDeluxe

  Here's my code: Public Class Form1 End Class Public Class Form1Handler Inherits Form1 Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click MsgBox("I") End Sub End Class I'm trying to get Form1Handler to process Form1's events automatically. How can I do this? Should I use a module instead? I'm doing this in VB 2010.

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• Exceptions and Access Violations in Paint events in Windows

  - by Patrick

  After executing some new code, my C++ application started to behave strange (incorrect or incomplete screen updates, sometimes no screen updates at all). After a while we found out that the new code is causing an Access Violation. Strange enough, the application simply keeps on running (but with the incorrect screen updates). At first we thought the problem was caused by a "try-catch(...)" construction (put there by an overactive ex-colleague), but several hours later (carefully inspecting the call stacks, adding many breakpoints, ...) we found out that if there's an Access Violation in a paint event, Windows catches it, and simply continues running the application. Is this normal behavior? Is it normal that Windows catches exceptions/errors during a paint event? Is there a way to disable this? (if not, it would mean that we have to always run in the debugger with all exceptions enabled while testing our code). Patrick

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• jtextfield keyevent handling issue

  - by vamsi

  doesn't .getKeyCode( ) return the key's int value? Because i have set my jtextfield to listen to keylistener, and in the keytyped method, i check what key has been pressed. Here's a snippet of my code: JTextField jtf = new JTextField( ); jtf.addKeyListener( this ); . . . public void keyTyped( KeyEvent e ) { if( e.getKeyCode( ) == KeyEvent.VK_ENTER ) System.out.println( "pressed enter" ); } but everytime i type enter in the jtextfield, nothing happens, ie nothing prints.

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• Default .NET exception handler

  - by ajs410

  So the other day my C# application crashed. Usually, with a .NET application, if you have an unhandled exception you get a nice error message with a stack trace. However, this time, I got a different dialog that just told me there was an error and offered to attach a Debugger, but there was no stack trace in the dialog and the machine it was running on had no debugger installed. What gives? Why don't I see the default .NET exception handler?

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• Event Handling in Chaco

  - by awegawef

  When hovering over a data point in Chaco, I would like a small text box to appear, with the text I desire. Also, when I click on a data point (or close enough), I would like my program to take a certain action. I have seen relevant parts of the Chaco documentation, but implementing them has proved difficult. Any help would be appreciated. Thanks.

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• ActiveRecord exceptions not rescued

  - by zoopzoop

  I have the following code block: unless User.exist?(...) begin user = User.new(...) # Set more attributes of user user.save! rescue ActiveRecord::RecordInvalid, ActiveRecord::RecordNotUnique => e # Check if that user was created in the meantime user = User.exists?(...) raise e if user.nil? end end The reason is, as you can probably guess, that multiple processes might call this method at the same time to create the user (if it doesn't already exist), so while the first one enters the block and starts initializing a new user, setting the attributes and finally calling save!, the user might already be created. In that case I want to check again if the user exists and only raise the exception if it still doesn't (= if no other process has created it in the meantime). The problem is, that regularly ActiveRecord::RecordInvalid exceptions are raised from the save! and not rescued from the rescue block. Any ideas? EDIT: Alright, this is weird. I must be missing something. I refactored the code according to Simone's tip to look like this: unless User.find_by_email(...).present? # Here we know the user does not exist yet user = User.new(...) # Set more attributes of user unless user.save # User could not be saved for some reason, maybe created by another request? raise StandardError, "Could not create user for order #{self.id}." unless User.exists?(:email => ...) end end Now I got the following exception: ActiveRecord::RecordNotUnique: Mysql::DupEntry: Duplicate entry '[email protected]' for key 'index_users_on_email': INSERT INTO `users` ... thrown in the line where it says 'unless user.save'. How can that be? Rails thinks the user can be created because the email is unique but then the Mysql unique index prevents the insert? How likely is that? And how can it be avoided?

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• Power error handling inside of sql function

  - by user172062

  I have a power function call inside of a sql function. What is the correct way to handle overflow and underflow conditions since I cannot use a Try Catch inside of a function. I am also trying to avoid modifying the ARITHABORT, ANSI_WARNINGS, and ARITHIGNORE settings in the calling code. GO CREATE FUNCTION TestPow() RETURNS DECIMAL(30, 14) AS BEGIN DECLARE @result FLOAT SET @result = POWER(10.0, 300) RETURN @result END GO SELECT dbo.TestPow()

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• Handling "Big" Integers in C#

  - by priyanka.sarkar

  How do I handle big integers in C#? I have a function that will give me the product of divisors: private static int GetDivisorProduct(int N, int product) { for (int i = 1; i < N; i++) { if (N % i == 0) { Console.WriteLine(i.ToString()); product *= i; } } return product; } The calling function is GetDivisorProduct(N, 1) If the result is bigger than 4 digits , I should obtain only the last 4 digits. ( E.g. If I give an input of 957, the output is 7493 after trimming out only the last four values. The actual result is 876467493.). Other sample inputs: If I give 10000, the output is 0. The BigInteger class has been removed from the C# library! How can I get the last four digits?

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• Are event handlerss in JavaScript called in order?

  - by musicfreak

  I know this is a simple question, but I haven't had the chance to test it in any browser other than Firefox. If I attach multiple event handlers to a single event on a single DOM element, are the event handlers guaranteed to be called in the order they were added? Or should I not rely on this behavior?

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• Complex sound handling (I.E. pitch change while looping)

  - by Matthew

  Hi everyone I've been meaning to learn Java for a while now (I usually keep myself in languages like C and Lua) but buying an android phone seems like an excellent time to start. now after going through the lovely set of tutorials and a while spent buried in source code I'm beginning to get the feel for it so what's my next step? well to dive in with a fully featured application with graphics, sound, sensor use, touch response and a full menu. hmm now there's a slight conundrum since i can continue to use cryptic references to my project or risk telling you what the application is but at the same time its going to make me look like a raving sci-fi nerd so bare with me for the brief... A semi-working sonic screwdriver (oh yes!) my grand idea was to make an animated screwdriver where sliding the controls up and down modulate the frequency and that frequency dictates the sensor data it returns. now I have a semi-working sound system but its pretty poor for what its designed to represent and I just wouldn't be happy producing a sub-par end product whether its my first or not. the problem : sound must begin looping when the user presses down on the control the sound must stop when the user releases the control when moving the control up or down the sound effect must change pitch accordingly if the user doesn't remove there finger before backing out of the application it must plate the casing of there device with gold (Easter egg ;P) now I'm aware of how monolithic the first 3 look and that's why I would really appreciate any help I can get. sorry for how bad this code looks but my general plan is to create the functional components then refine the code later, no good painting the walls if the roofs not finished. here's my user input, he set slide stuff is used in the graphics for the control @Override public boolean onTouchEvent(MotionEvent event) { //motion event for the screwdriver view if(event.getAction() == MotionEvent.ACTION_DOWN) { //make sure the users at least trying to touch the slider if (event.getY() > SonicSlideYTop && event.getY() < SonicSlideYBottom) { //power setup, im using 1.5 to help out the rate on soundpool since it likes 0.5 to 1.5 SonicPower = 1.5f - ((event.getY() - SonicSlideYTop) / SonicSlideLength); //just goes into a method which sets a private variable in my sound pool class thing mSonicAudio.setPower(1, SonicPower); //this handles the slides graphics setSlideY ( (int) event.getY() ); @Override public boolean onTouchEvent(MotionEvent event) { //motion event for the screwdriver view if(event.getAction() == MotionEvent.ACTION_DOWN) { //make sure the users at least trying to touch the slider if (event.getY() > SonicSlideYTop && event.getY() < SonicSlideYBottom) { //power setup, im using 1.5 to help out the rate on soundpool since it likes 0.5 to 1.5 SonicPower = 1.5f - ((event.getY() - SonicSlideYTop) / SonicSlideLength); //just goes into a method which sets a private variable in my sound pool class thing mSonicAudio.setPower(1, SonicPower); //this handles the slides graphics setSlideY ( (int) event.getY() ); //this is from my latest attempt at loop pitch change, look for this in my soundPool class mSonicAudio.startLoopedSound(); } } if(event.getAction() == MotionEvent.ACTION_MOVE) { if (event.getY() > SonicSlideYTop && event.getY() < SonicSlideYBottom) { SonicPower = 1.5f - ((event.getY() - SonicSlideYTop) / SonicSlideLength); mSonicAudio.setPower(1, SonicPower); setSlideY ( (int) event.getY() ); } } if(event.getAction() == MotionEvent.ACTION_UP) { mSonicAudio.stopLoopedSound(); SonicPower = 1.5f - ((event.getY() - SonicSlideYTop) / SonicSlideLength); mSonicAudio.setPower(1, SonicPower); } return true; } and here's where those methods end up in my sound pool class its horribly messy but that's because I've been trying a ton of variants to get this to work, you will also notice that I begin to hard code the index, again I was trying to get the methods to work before making them work well. package com.mattster.sonicscrewdriver; import java.util.HashMap; import android.content.Context; import android.media.AudioManager; import android.media.SoundPool; public class SoundManager { private float mPowerLvl = 1f; private SoundPool mSoundPool; private HashMap mSoundPoolMap; private AudioManager mAudioManager; private Context mContext; private int streamVolume; private int LoopState; private long mLastTime; public SoundManager() { } public void initSounds(Context theContext) { mContext = theContext; mSoundPool = new SoundPool(2, AudioManager.STREAM_MUSIC, 0); mSoundPoolMap = new HashMap<Integer, Integer>(); mAudioManager = (AudioManager)mContext.getSystemService(Context.AUDIO_SERVICE); streamVolume = mAudioManager.getStreamVolume(AudioManager.STREAM_MUSIC); } public void addSound(int index,int SoundID) { mSoundPoolMap.put(1, mSoundPool.load(mContext, SoundID, 1)); } public void playUpdate(int index) { if( LoopState == 1) { long now = System.currentTimeMillis(); if (now > mLastTime) { mSoundPool.play(mSoundPoolMap.get(1), streamVolume, streamVolume, 1, 0, mPowerLvl); mLastTime = System.currentTimeMillis() + 250; } } } public void stopLoopedSound() { LoopState = 0; mSoundPool.setVolume(mSoundPoolMap.get(1), 0, 0); mSoundPool.stop(mSoundPoolMap.get(1)); } public void startLoopedSound() { LoopState = 1; } public void setPower(int index, float mPower) { mPowerLvl = mPower; mSoundPool.setRate(mSoundPoolMap.get(1), mPowerLvl); } } ah ha! I almost forgot, that looks pretty ineffective but I omitted my thread which actuality updates it, nothing fancy it just calls : mSonicAudio.playUpdate(1); thanks in advance, Matthew

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• What Windows editor has CORRECT EOL whitespace handling?

  - by blueshift

  I'm looking for a Windows text editor for programming that handles EOL whitespace CORRECTLY, which for my idea of correct means: Strip all EOL whitespace on save, EXCEPT on lines that I haven't edited. This is to minimise the amount of EOL whitespace evil in my world, but not pollute SCM diff/blame with whitespace-only fixes (I have to deal with old / other people's code). I have played with TextPad, Notepad++, Kodomo Edit and Programmer's Notepad 2, and found all of them lacking. Also: I don't get along with vi, and I am unsure about Emacs on Windows. @Matti Virkkunen: I could mess with diff, but I want to fix the problem, not the symptoms. Fixing diff means all my, others, and server side diff tools need to be fixed, and doesn't fix space/noise/hash change issues in SCM. Example pet hate using that system: "update" tells me a file has changed. Diff shows no changes.

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• Best practices for handling unique constraint violation

  - by umesh awasthi

  Hi All, While working in my application i came across a situation in which there are likely chances to Unque Constraints Violation.I have following options Catch the exception and throw it back to UI At UI check for the exception and show approrpriate Error Message This is something different idea is to Check in advance about the existance of the given Unique value before starting the whole operation. My Question is what might be the best practice to handle such situation.Currently we are using combo of Struts2+Spring 3.x+Hibernate 3.x Thanks in advance

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• Logging exceptions to database in NServiceBus

  - by IGoor

  If an exception occurs in my MessageHandler I want to write the exception details to my database. How do I do this? Obviously, I cant just catch the exception, write to database, and rethrow it since NSB rollbacks all changes. (IsTransactional is set to true) I tried adding logging functionality in a seperate handler, which I caledl using SendLocal if an exception occured, but this does not work: public void Handle(MessageItem message) { try { DoWork(); } catch(Exception exc) { Bus.SendLocal(new ExceptionMessage(exc.Message)); throw; } } I also tried using Log4Net with a custom appender, but this also rolled back. Configure.With() .Log4Net<DatabaseAppender>(a => a.Log = "Log") appender: public class DatabaseAppender : log4net.Appender.AppenderSkeleton { public string Log { get; set; } protected override void Append(log4net.Core.LoggingEvent loggingEvent) { if (loggingEvent.ExceptionObject != null) WriteToDatabase(loggingEvent.ExceptionObject); } } Is there anyway to log unhandled exceptions in the messagehandler when IsTransactional is true? Thanks in advance.

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• How to create custom exception handler for custom controls or extension methods.

  - by Shantanu Gupta

  I am creating an extension method in C# to retrieve some value from datagridview. Here if a user gives column name that doesnot exists then i want this function to throw an exception that can be handled at the place where this function will be called. How can i achieve this. public static T Value<T>(this DataGridView dgv, int RowNo, string ColName) { if (!dgv.Columns.Contains(ColName)) throw new ArgumentException("Column Name " + ColName + " doesnot exists in DataGridView."); return (T)Convert.ChangeType(dgv.Rows[RowNo].Cells[ColName].Value, typeof(T)); }

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• handling Concurrency in SQL SERVER 2005

  - by sameer

  Hi, I have one question for you, if you can answer and refer resource it will be great help. I have a scenario where i need to create a appointment slot and a serial no for each slot memberwise. ex: Member Id |App Slot # 1|1 1|2 2|1 2|2 1|3 what im doing is take the Max slot number,increamenting it and insert it memberwise. but the problem is concurrent user can create a slot when i take the max slot after that if any other user insert the slot the value that im working with is no more valid, how to over come this problem Thanks & Regards, Sameer

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