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• handle button event programatically

  - by chaitanya

  how to handle button event programatically ?

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• Simple Mouse Move Event in F# with Winforms

  - by MarkPearl

  This evening I had the pleasure of reading one of ThomasP’s blog posts on first class events. It was an excellent read, and I thought I would make a brief derivative of his post to explore some of the basics. In Thomas’s post he has a form with an ellipse on it that when he clicks on the ellipse it pops up a message box with the button clicked… awesome. Something that got me on the post though was the code similar to the one below… // React to Mouse Move events on the form let evtMessages = frm.MouseMove |> Event.map (fun mi -> mi.Location.ToString()) |> Event.map (sprintf "Hey, you clicked on the ellipse.\nUsing: %s") |> Event.add (MessageBox.Show >> ignore) The MessageBox is a function with a string passed into it. What if I wanted to rather change a mutable value holder instead, how would the syntax go for that? Immediately the thought came to me of anonymous functions. I’ve used them before to do something like this… let HelloPerson personName = "Hello " + personName |> fun(x) -> Console.WriteLine(x) So using the same approach I adapted the event code to instead of showing a Message Box with a string passed in to it, to rather change the forms header. |> Event.map (sprintf "Your mouse position is %s") |> Event.add(fun(x) -> frm.Text <- x) Okay… it looks a bit weird with the –> x <- syntax, but makes sense and works… The next thing I wanted to do was change Thomas’s code sample from having an ellipse, and reacting to the position of the mouse and click, to rather trigger the event whenever the mouse moved. This simple involved removing some filtering code. Finally I wanted the code to work as a FSharp Project without having to run through the F# interactive. To achieve this I just needed to find out how to trigger the window event loop. This can be achieved with the code below… // Program eventloop while frm.Created do Application.DoEvents()   So lets look at the complete code sample… #light open System open System.Drawing open System.Windows.Forms // Create the main form let frm = new Form(ClientSize=Size(600,400)) // React to Mouse Move events on the form let evtMessages = frm.MouseMove |> Event.map (fun mi -> mi.Location.ToString()) |> Event.map (sprintf "Your mouse position is %s") |> Event.add(fun(x) -> frm.Text <- x) // Show the form frm.Show() // Program eventloop while frm.Created do Application.DoEvents()

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• Android Touch Event Collision Detection

  - by chrissb

  I'm relatively new to both Java and Android, so hopefully the problem I'm having is stemming from something pretty minor that I've overlooked. I've got a (very early stage) game that I've started working on, for Android using Java. At this stage, when the user touches the screen, if they touched a point at which there is an enemy, the enemies health is decreased and they become immobile (for the current implementation at least). The issue that I'm having is that the touch detection doesn't always seem to work. I've got a testing sprite set up that goes to the eventX and eventY coordinates of the touch down event, and it always seems to collide with the enemy object. Yet, the enemy doesn't always register as being hit, and sometimes a hit is registered when the sprite indicates the touch coordinates were outside of the enemies bounding box. I realise that this probably doesn't mean much without any code, so here's what I've got so far. Be gentle, as this is literally my first attempt at something more than basic movement etc. First off, the MainGamePanel class registers the touch event, and informs the levelmanager class (which is what I set up to monitor/handle enemies) public boolean onTouchEvent(MotionEvent event) { if (event.getAction() == MotionEvent.ACTION_DOWN){ levelManager.handleActionDown((int)event.getX(), (int)event.getY()); targetX=event.getX(); targetY=event.getY(); } if (event.getAction() == MotionEvent.ACTION_MOVE) { //the gestures } if (event.getAction() == MotionEvent.ACTION_UP) { //touch was released } return true; } From there, in the levelmanager class the touch event is passed on to all of the enemies within a list array: public static void handleActionDown(int eventX,int eventY){ hit=false; for (enemy1 en : enemy1array){ en.handleActionDown(eventX, eventY); } } The rest of the collision code is handled within the enemies handleActionDown function: public void handleActionDown(int eventX, int eventY) { if(eventX>this.x-enemy1bitmap.getWidth() && eventX<this.x+enemy1bitmap.getWidth() && eventY>this.y-enemy1bitmap.getHeight() && eventY<this.x+enemy1bitmap.getHeight()){ takeDamage(1); levelmanager.setHit(); } } I should probably be using getWidth()/2 and getHeight()/2 for it to be more accurate, but I expanded the area to test this - although I've noticed no improvement. At this stage, the games detection over whether or not the enemy is hit is spotty at best. Generally it takes two or three attempts before a collision is successfully registered, even though the sprite that is being used for testing and set to the eventX and eventY coordinates always indicates that the collision should have worked. Hopefully someone can steer me in the right direction here, and if more information is needed, ask away! Cheers, -Chris

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• Image container instead of event object in image load event handler

  - by avok00

  I stumbled upon a very strange thing. In FF 3.6 (not tested others yet) I add onload handler to an image like this: imgRef.addEventListener("load", activateLink, false); When load event fires, in activateLink(evt) the evt paramater is not an event, but the "a" tag that contains the image. Why is this? function activateLink(evt) { // evt turns out to be a refference to <a> tag (HTMLAnchorElement) that contains the image. // Actually two of them. Both dynamically added with addElement. } I remembered another fact that may be relevant. I have multiple images with the same src that all have registered this same event handler activateLink. Could this be the problem?

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• Perl - How to save an handler as an attribute in order to use in outside a module

  - by Zwik

  Ultimately, what I want to do is to start a process in a module and parse the output in real time in another script. What I want to do : Open a process Handler (IPC) Use this attribute outside of the Module How I'm trying to do it and fail : Open the process handler Save the handler in a module's attribute Use the attribute outside the module. Code example : #module.pm self->{PROCESS_HANDLER}; sub doSomething{ ... open( self->{PROCESS_HANDLER}, "run a .jar 2>&1 |" ); ... } #perlScript.pl my $module = new module(...); ... $module->doSomething(); ... while( $module->{PROCESS_HANDLER} ){ ... }

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• ReSharper C# Live Template for Declaring Routed Event

  - by Bart Read

  Here's another WPF ReSharper Live Template for you. This one is for declaring standalone routed events of any type. Again, it's pretty simple:        #region $EVENTNAME$ Routed Event       public static readonly RoutedEvent $EVENTNAME$Event = EventManager.RegisterRoutedEvent(            "$EVENTNAME$",           RoutingStrategy.$ROUTINGSTRATEGY$,           typeof( $EVENTHANDLERDELEGATE$ ),           typeof( $DECLARINGTYPE$ ) );       public event $EVENTHANDLERDELEGATE$ $EVENTNAME$       {           add { AddHandler( $EVENTNAME$Event, value ); }           remove { RemoveHandler( $EVENTNAME$Event, value ); }       }       protected virtual void On$EVENTNAME$()       {           RaiseEvent( new $EVENTARGSTYPE$( $EVENTNAME$Event, this ) );           $END$       }       #endregion Here are my previous posts along the same lines: ReSharper C# Live Template for Read-Only Dependency Property and Routed Event Boilerplate ReSharper C# Live Template for Dependency Property and Property Change Routed Event Boilerplate Code Enjoy! Technorati Tags: resharper,live template,c#,routed event,wpf,boilerplate,code generation

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• Introduction to Extended Events

  - by extended_events

  For those fighting with all the Extended Event terminology, let's step back and have a small overall Introduction to Extended Events. This post will give you a simplified end to end view through some of the elements in Extended Events. Before we start, let’s review the first Extented Events that we are going to use: -          Events: The SQL Server code is populated with event calls that, by default, are disabled. Adding events to a session enables those event calls. Once enabled, they will execute the set of functionality defined by the session. -          Target: This is an Extended Event Object that can be used to log event information. Also it is important to understand the following Extended Event concept: -          Session: Server Object created by the user that defines functionality to be executed every time a set of events happen.   It’s time to write a small “Hello World” using Extended Events. This will help understand the above terms. We will use: -          Event sqlserver. error_reported: This event gets fired every time that an error happens in the server. -          Target package0.asynchronous_file_target: This target stores the event data in disk. -          Session: We will create a session that sends all the error_reported events to the ring buffer. Before we get started, a quick note: Don’t run this script in a production environment. Even though, we are going just going to be raise very low severity user errors, we don't want to introduce noise in our servers. -- TRIES TO ELIMINATE PREVIOUS SESSIONS BEGIN TRY       DROP EVENT SESSION test_session ON SERVER END TRY BEGIN CATCH END CATCH GO   -- CREATES THE SESSION CREATE EVENT SESSION test_session ON SERVER ADD EVENT sqlserver.error_reported ADD TARGET package0.asynchronous_file_target -- CONFIGURES THE FILE TARGET (set filename = 'c:\temp\data1.xel' , metadatafile = 'c:\temp\data1.xem') GO   -- STARTS THE SESSION ALTER EVENT SESSION test_session ON SERVER STATE = START GO   -- GENERATES AN ERROR RAISERROR (N'HELLO WORLD', -- Message text.            1, -- Severity,            1, 7, 3, N'abcde'); -- Other parameters GO   -- STOPS LISTENING FOR THE EVENT ALTER EVENT SESSION test_session ON SERVER STATE = STOP GO   -- REMOVES THE EVENT SESSION FROM THE SERVER DROP EVENT SESSION test_session ON SERVER GO -- REMOVES THE EVENT SESSION FROM THE SERVER select CAST(event_data as XML) as event_data from sys.fn_xe_file_target_read_file ('c:\temp\data1*.xel','c:\temp\data1*.xem', null, null) This query will output the event data with our first hello world in the Extended Event format: <event name="error_reported" package="sqlserver" id="100" version="1" timestamp="2010-02-27T03:08:04.210Z"><data name="error"><value>50000</value><text /></data><data name="severity"><value>1</value><text /></data><data name="state"><value>1</value><text /></data><data name="user_defined"><value>true</value><text /></data><data name="message"><value>HELLO WORLD</value><text /></data></event> More on parsing event data in this post: Reading event data 101 Now let's move that lets move on to the other three Extended Event objects: -          Actions. This Extended Objects actions get executed before events are published (stored in buffers to be transferred to the targets). Currently they are used additional data (like the TSQL Statement related to an event, the session, the user) or generate a mini dump.   -          Predicates: Predicates express are logical expressions that specify what predicates to fire (E.g. only listen to errors with a severity greater than 16). This are composed of two Extended Objects: o   Predicate comparators: Defines an operator for a pair of values. Examples: §  Severity > 16 §  error_message = ‘Hello World!!’ o   Predicate sources: These are values that can be also used by the predicates. They are generic data that isn’t usually provided in the event (similar to the actions). §  Sqlserver.username = ‘Tintin’ As logical expressions they can be combined using logical operators (and, or, not).  Note: This pair always has to be first an event field or predicate source and then a value         Let’s do another small Example. We will trigger errors but we will use the ones that have severity >= 10 and the error message != ‘filter’. To verify this we will use the action sql_text that will attach the sql statement to the event data: -- TRIES TO ELIMINATE PREVIOUS SESSIONS BEGIN TRY       DROP EVENT SESSION test_session ON SERVER END TRY BEGIN CATCH END CATCH GO   -- CREATES THE SESSION CREATE EVENT SESSION test_session ON SERVER ADD EVENT sqlserver.error_reported       (ACTION (sqlserver.sql_text) WHERE severity = 2 and (not (message = 'filter'))) ADD TARGET package0.asynchronous_file_target -- CONFIGURES THE FILE TARGET (set filename = 'c:\temp\data2.xel' , metadatafile = 'c:\temp\data2.xem') GO   -- STARTS THE SESSION ALTER EVENT SESSION test_session ON SERVER STATE = START GO   -- THIS EVENT WILL BE FILTERED BECAUSE SEVERITY != 2 RAISERROR (N'PUBLISH', 1, 1, 7, 3, N'abcde'); GO -- THIS EVENT WILL BE FILTERED BECAUSE MESSAGE = 'FILTER' RAISERROR (N'FILTER', 2, 1, 7, 3, N'abcde'); GO -- THIS ERROR WILL BE PUBLISHED RAISERROR (N'PUBLISH', 2, 1, 7, 3, N'abcde'); GO   -- STOPS LISTENING FOR THE EVENT ALTER EVENT SESSION test_session ON SERVER STATE = STOP GO   -- REMOVES THE EVENT SESSION FROM THE SERVER DROP EVENT SESSION test_session ON SERVER GO -- REMOVES THE EVENT SESSION FROM THE SERVER select CAST(event_data as XML) as event_data from sys.fn_xe_file_target_read_file ('c:\temp\data2*.xel','c:\temp\data2*.xem', null, null)   This last statement will output one event with the following data: <event name="error_reported" package="sqlserver" id="100" version="1" timestamp="2010-03-05T23:15:05.481Z">   <data name="error">     <value>50000</value>     <text />   </data>   <data name="severity">     <value>2</value>     <text />   </data>   <data name="state">     <value>1</value>     <text />   </data>   <data name="user_defined">     <value>true</value>     <text />   </data>   <data name="message">     <value>PUBLISH</value>     <text />   </data>   <action name="sql_text" package="sqlserver">     <value>-- THIS ERROR WILL BE PUBLISHED RAISERROR (N'PUBLISH', 2, 1, 7, 3, N'abcde'); </value>     <text />   </action> </event> If you see more events, check if you have deleted previous event files. If so, please run   -- Deletes previous event files EXEC SP_CONFIGURE GO EXEC SP_CONFIGURE 'xp_cmdshell', 1 GO RECONFIGURE GO XP_CMDSHELL 'del c:\temp\data*.xe*' GO   or delete them manually.   More Info on Events: Extended Event Events More Info on Targets: Extended Event Targets More Info on Sessions: Extended Event Sessions More Info on Actions: Extended Event Actions More Info on Predicates: Extended Event Predicates Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• Showing Egde Shaped Event Duration in StreamInsight using Debugger

  Whilst writing some courseware I wanted to be able to see the start and end times of Edge shaped events from within the debugger.  A quick recap on Edge events At the start of the event you do not know the end time and most probably cannot work it out or you should be using one of the other shapes. You enqueue an event (Start Edge) with the start time and payload of the event.  The end time of the event is set to infinity When you see the end edge come through, you enqueue another event (End Edge) with the previous start time and payload and restate the event’s end time.  This is the Retract Event All seems simple enough.  The problem is the debugger is a little shy about showing you what you need but you can get it to show you everything by also reading this article Here’s what I mean. Here is what the Event Debugger looks like by default when viewing 2 complete edge events.  Notice how all the end times are set to infinity   The above does not tell you for how long an event was valid.  I then add the “NewEndTime” column to the debugger output and there I can now see the duration of events.  You will see the Retract events (End Edge) have the same start time and payload as their respective start events (Start Edge)   You can follow the exact same logic when looking at Interval shape events.  They look a little different on the output adapter but using this article you can easily see what is happening.

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• Non-Dom Element Event Binding with jQuery

  - by Rick Strahl

  Yesterday I had a short discussion with Dave Reed on Twitter regarding setting up fake ‘events’ on objects that are hookable. jQuery makes it real easy to bind events on DOM elements and with a little bit of extra work (that I didn’t know about) you can also set up binding to non-DOM element ‘event’ bindings. Assume for a second that you have a simple JavaScript object like this: var item = { sku: "wwhelp" , foo: function() { alert('orginal foo function'); } }; and you want to be notified when the foo function is called. You can use jQuery to bind the handler like this: $(item).bind("foo", function () { alert('foo Hook called'); } ); Binding alone won’t actually cause the handler to be triggered so when you call: item.foo(); you only get the ‘original’ message. In order to fire both the original handler and the bound event hook you have to use the .trigger() function: $(item).trigger("foo"); Now if you do the following complete sequence: var item = { sku: "wwhelp" , foo: function() { alert('orginal foo function'); } }; $(item).bind("foo", function () { alert('foo hook called'); } ); $(item).trigger("foo"); You’ll see the ‘hook’ message first followed by the ‘original’ message fired in succession. In other words, using this mechanism you can hook standard object functions and chain events to them in a way similar to the way you can do with DOM elements. The main difference is that the ‘event’ has to be explicitly triggered in order for this to happen rather than just calling the method directly. .trigger() relies on some internal logic that checks for event bindings on the object (attached via an expando property) which .trigger() searches for in its bound event list. Once the ‘event’ is found it’s called prior to execution of the original function. This is pretty useful as it allows you to create standard JavaScript objects that can act as event handlers and are effectively hookable without having to explicitly override event definitions with JavaScript function handlers. You get all the benefits of jQuery’s event methods including the ability to hook up multiple events to the same handler function and the ability to uniquely identify each specific event instance with post fix string names (ie. .bind("MyEvent.MyName") and .unbind("MyEvent.MyName") to bind MyEvent). Watch out for an .unbind() Bug Note that there appears to be a bug with .unbind() in jQuery that doesn’t reliably unbind an event and results in a elem.removeEventListener is not a function error. The following code demonstrates: var item = { sku: "wwhelp", foo: function () { alert('orginal foo function'); } }; $(item).bind("foo.first", function () { alert('foo hook called'); }); $(item).bind("foo.second", function () { alert('foo hook2 called'); }); $(item).trigger("foo"); setTimeout(function () { $(item).unbind("foo"); // $(item).unbind("foo.first"); // $(item).unbind("foo.second"); $(item).trigger("foo"); }, 3000); The setTimeout call delays the unbinding and is supposed to remove the event binding on the foo function. It fails both with the foo only value (both if assigned only as “foo” or “foo.first/second” as well as when removing both of the postfixed event handlers explicitly. Oddly the following that removes only one of the two handlers works: setTimeout(function () { //$(item).unbind("foo"); $(item).unbind("foo.first"); // $(item).unbind("foo.second"); $(item).trigger("foo"); }, 3000); this actually works which is weird as the code in unbind tries to unbind using a DOM method that doesn’t exist. <shrug> A partial workaround for unbinding all ‘foo’ events is the following: setTimeout(function () { $.event.special.foo = { teardown: function () { alert('teardown'); return true; } }; $(item).unbind("foo"); $(item).trigger("foo"); }, 3000); which is a bit cryptic to say the least but it seems to work more reliably. I can’t take credit for any of this – thanks to Dave Reed and Damien Edwards who pointed out some of these behaviors. I didn’t find any good descriptions of the process so thought it’d be good to write it down here. Hope some of you find this helpful.© Rick Strahl, West Wind Technologies, 2005-2010Posted in jQuery  

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• A good substitute for ASMX web service methods, but not a general handler

  - by Saeed Neamati

  The best thing I like about ASP.NET MVC, is that you can directly call a server method (called action), from the client. This is so convenient, and so straightforward, that I really like to implement such a model in ASP.NET WebForms too. However, in ASP.NET WebForms, to call a server method from the client, you should either use Page Methods, or Web Services, both of which use SOAP as their communication protocol (though JSON can also be used). There is also another substitution, which is using Generic Handlers. The problem with them however is that, a separate Generic Handler should be written for each server method. In other words, each Generic Handler works like a simple method. Is there anyway else to imitate MVC model in ASP.NET WebForms? Please note that I can't change to MVC platform right now, cause the project at our hand is a big project and we don't have required resources and time to change our platform. What we seek, is a simple MVC model implementation for our AJAX calls. A problem that we have with Web Services, is the known problem of SoapException, and we're not interested in creating custom SoapExctensions.

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• Event Driven Programming 101

  - by JHarley1

  Good Morning, I previously asked the Q. of how Event Handlers Work (which I got a great answer for). I would now like to understand the basics of how are events are associated with on-screen objects? An explanation of how Events are associated with on Screen Objects: The application registers the Event, the Event Handler and the Component with the GUI Server. When an Event is detected the GUI Server has to link an Event to a Window and then to a Component, it then consults the Event / Component Table to identify which Handler (s) to be executed. I am having problems finding resources/papers that have mention of this process - especially of a Event / Component Table - can anyone clarify?

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• WCF REST Error Handler

  - by Elton Stoneman

  I’ve put up on GitHub a sample WCF error handler for REST services, which returns proper HTTP status codes in response to service errors.   The code is very simple – a ServiceBehavior implementation which can be specified in config to tag the RestErrorHandler to a service. Any uncaught exceptions will be routed to the error handler, which sets the HTTP status code and description in the response, based on the type of exception.   The sample defines a ClientException which can be thrown in code to indicate a problem with the client’s request, and the response will be a status 400 with a friendly error message:       throw new ClientException("Invalid userId. Must be provided as a positive integer");   - responds:   Request URL http://localhost/Sixeyed.WcfRestErrorHandler.Sample/ErrorProneService.svc/lastLogin?userId=xyz   Error Status Code: 400, Description: Invalid userId. Must be provided as a positive integer   Any other uncaught exceptions are hidden from the client. The full details are logged with a GUID to identify the error, and the response to the client is a status 500 with a generic message giving them the GUID to follow up on:       var iUserId = 0;     var dbz = 1 / iUserId;   - logs the divide-by-zero error and responds:   Request URL http://localhost/Sixeyed.WcfRestErrorHandler.Sample/ErrorProneService.svc/dbz     Error Status Code: 500, Description: Something has gone wrong. Please contact our support team with helpdesk ID: C9C5A968-4AEA-48C7-B90A-DEC986F80DA5   The sample demonstrates two techniques for building the response. For client exceptions, a friendly HTML response is sent in the body as well as the status code and description. Personally I prefer not to do that – it doesn’t make sense to get a 400 error and find text/html when you’re expecting application/json, but it’s easy to do if that’s the functionality you want. The other option is to send an empty response, which the sample does with server exceptions.   The obvious extension is to have multiple exceptions representing all the status codes you want to provide, then your code is as simple as throwing the relevant exception – UnauthorizedException, ForbiddenExeption, NotImplementedException etc – anywhere in the stack, and it will be handled nicely.

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• Difference event.result and event.message.body in Flex

  - by theband

  What is the difference between event.result and event.message.body in Flex. private function resultHandler(evt:ResultEvent):void { result_text.text = evt.message.body.toString(); } private function resultHandler(evt:ResultEvent):void { result_text.text = evt.result.toString(); }

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• Help with c# event listening and usercontrols

  - by Jen

  OK so I have a page which has a listview on it. Inside the item template of the listview is a usercontrol. This usercontrol is trying to trigger an event so that the hosting page can listen to it. My problem is that the event is not being triggered as the handler is null. (ie. EditDateRateSelected is my handler and its null when debugging) protected void lnkEditDate_Click(object sender, EventArgs e) { if (EditDateRateSelected != null) EditDateRateSelected(Convert.ToDateTime(((LinkButton)frmViewRatesDate.Row.FindControl("lnkEditDate")).Text)); } On the item data bound of my listvew is where I'm adding my event handlers protected void PropertyAccommodationRates1_ItemDataBound(object sender, ListViewItemEventArgs e) { if (e.Item.ItemType == ListViewItemType.DataItem) { UserControls_RatesEditDate RatesViewDate1 = (UserControls_RatesEditDate)e.Item.FindControl("RatesViewDate1"); RatesViewDate1.EditDateRateSelected += new UserControls_RatesEditDate.EditDateRateEventHandler(RatesEditDate1_EditDateRateSelected); RatesViewDate1.PropertyID = (int)Master.PropertyId; if (!String.IsNullOrEmpty(Accommodations1.SelectedValue)) { RatesViewDate1.AccommodationTypeID = Convert.ToInt32(Accommodations1.SelectedValue); } else { RatesViewDate1.AccommodationTypeID = 0; } RatesViewDate1.Rate = (PropertyCMSRate)((ListViewDataItem)e.Item).DataItem; } } My event code all works fine if the control is inside the page and on page load I have the line: RatesEditDate1.EditDateRateSelected += new UserControls_RatesEditDate.EditDateRateEventHandler(RatesEditDate1_EditDateRateSelected); But obviously I need listen for events inside the listviewcontrols. Any advice would be greatly appreciated. I have tried setting EnableViewState to true for my listview but that hasn't made a difference. Is there somewhere else I'm supposed to be wiring up the control handler? Note - apologies if I've got my terminology wrong and I'm referring to delegates as handlers and such :)

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• ASP .NET Added Event Handlers to buttons on Page_Load. Event handlers do not fire the first click, b

  - by John

  Background: I am customizing an existing ASP .NET / C# application. It has it's own little "framework" and conventions for developers to follow when extending/customizing its functionality. I am currently extending some of it's administrative functionality, to which the framework provides a contract to enforce implementation of the GetAdministrationInterface() method, which returns System.Web.UI.Control. This method is called during the Page_Load() method of the page hosting the GUI interface. Problem: I have three buttons in my GUI, each of which have been assigned an Event Handler. My administration GUI loads up perfectly fine, but clicking any of the buttons doesn't do what I expect them to do. However, when I click them a second time, the buttons work. I placed breakpoints at the the beginning of each event handler method and stepped through my code. On the first click, none of the event handlers are triggered. On the second click, they are triggered. Any ideas? Example of Button Definition Button btn = new Button(); btn.Text = "Click Me Locked Screen"; bth.Click += new EventHandler(Btn_Click); Example of Event Handler Method Definition void Btn_Click(object sender, EventArgs e) { // Do Something }

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• Calling the LWRP from the Exception Handler

  - by Sarah Haskins

  Is it possible to call out to a Provider (LWRP) from a Chef Exception Handler? I think my Provider is out of scope, but I don't know if what I am trying to do is possible? or advisable? Here is my provider code (cookbooks/config/provider/signal.rb): action :failure do Chef::Log.info("Yeah success") end Here is my exception handler code (exception_handler/handlers/exceptionHandler.rb): require 'chef/handler' config_signal "signal" do action :nothing end class Chef class Handler class LogCollector < Chef::Handler notifies :failure, resources(:config_signal => signal) end end end Also, if anyone has a good recommendation for general reading about scope in the context of Chef I'd appreciate it.

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• Java, Jacob and Microsoft Outlook events: Receiving "Can't find event iid" Error

  - by Adam Paynter

  I am writing a Java program that interacts with Microsoft Outlook using the Jacob library (bridges COM and Java). This program creates a new MailItem, displaying its Inspector window to the user. I wish to subscribe to the inspector's Close event to know when the user is finished editing their mail item. To subscribe to the event, I followed the instructions in Jacob's documentation (about 2⁄3 down the page): The current [event] model is conceptually similar to the Visual Basic WithEvents construct. Basically, I provide a class called com.jacob.com.DispatchEvents which has a constructor that takes a source object (of type com.jacob.com.Dispatch) and a target object (of any type). The source object is queried for its IConnectionPointContainer interface and I attempt to obtain an IConnectionPoint for its default source interface (which I obtain from IProvideClassInfo). At the same time, I also create a mapping of DISPID's for the default source interface to the actual method names. I then use the method names to get jmethodID handles from the target Java object. All event methods currently must have the same signature: one argument which is a Java array of Variants, and a void return type. Here is my InspectorEventHandler class, conforming to Jacob's documentation: public class InspectorEventHandler { public void Activate(Variant[] arguments) { } public void BeforeMaximize(Variant[] arguments) { } public void BeforeMinimize(Variant[] arguments) { } public void BeforeMove(Variant[] arguments) { } public void BeforeSize(Variant[] arguments) { } public void Close(Variant[] arguments) { System.out.println("Closing"); } public void Deactivate(Variant[] arguments) { } public void PageChange(Variant[] arguments) { } } And here is how I subscribe to the events using this InspectorEventHandler class: Object outlook = new ActiveXComponent("Outlook.Application"); Object mailItem = Dispatch.call(outlook, "CreateItem", 0).getDispatch(); Object inspector = Dispatch.get(mailItem, "GetInspector").getDispatch(); InspectorEventHandler eventHandler = new InspectorEventHandler(); // This supposedly registers eventHandler with the inspector new DispatchEvents((Dispatch) inspector, eventHandler); However, the last line fails with the following exception: Exception in thread "main" com.jacob.com.ComFailException: Can't find event iid at com.jacob.com.DispatchEvents.init(Native Method) at com.jacob.com.DispatchEvents.(DispatchEvents.java) at cake.CakeApplication.run(CakeApplication.java:30) at cake.CakeApplication.main(CakeApplication.java:15) couldn't get IProvideClassInfo According to Google, a few others have also received this error. Unfortunately, none of them have received an answer. I am using version 1.7 of the Jacob library, which claims to prevent this problem: Version 1.7 also includes code to read the type library directly from the progid. This makes it possible to work with all the Microsoft Office application events, as well as IE5 events. For an example see the samples/test/IETest.java example. I noticed that the aforementioned IETest.java file subscribes to events like this: new DispatchEvents((Dispatch) ieo, ieE,"InternetExplorer.Application.1"); Therefore, I tried subscribing to my events in a similar manner: new DispatchEvents((Dispatch) inspector, eventHandler, "Outlook.Application"); new DispatchEvents((Dispatch) inspector, eventHandler, "Outlook.Application.1"); new DispatchEvents((Dispatch) inspector, eventHandler, "Outlook.Application.12"); All these attempts failed with the same error.

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• jquery: is there a fail handler for $.post in Jquery?

  - by Jux

  When $.post succeeds, there is a success handler for it. What happens if it fails? Is there a similar handler that we can use for this case, so that we can inform the user that something is not happening right?

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• Several client waiting for the same event

  - by ff8mania

  I'm developing a communication API to be used by a lot of generic clients to communicate with a proprietary system. This proprietary system exposes an API, and I use a particular classes to send and wait messages from this system: obviously the system alert me that a message is ready using an event. The event is named OnMessageArrived. My idea is to expose a simple SendSyncMessage(message) method that helps the user/client to simply send a message and the method returns the response. The client: using ( Communicator c = new Communicator() ) { response = c.SendSync(message); } The communicator class is done in this way: public class Communicator : IDisposable { // Proprietary system object ExternalSystem c; String currentRespone; Guid currentGUID; private readonly ManualResetEvent _manualResetEvent; private ManualResetEvent _manualResetEvent2; String systemName = "system"; String ServerName = "server"; public Communicator() { _manualResetEvent = new ManualResetEvent(false); //This methods are from the proprietary system API c = SystemInstance.CreateInstance(); c.Connect(systemName , ServerName); } private void ConnectionStarter( object data ) { c.OnMessageArrivedEvent += c_OnMessageArrivedEvent; _manualResetEvent.WaitOne(); c.OnMessageArrivedEvent-= c_OnMessageArrivedEvent; } public String SendSync( String Message ) { Thread _internalThread = new Thread(ConnectionStarter); _internalThread.Start(c); _manualResetEvent2 = new ManualResetEvent(false); String toRet; int messageID; currentGUID = Guid.NewGuid(); c.SendMessage(Message, "Request", currentGUID.ToString()); _manualResetEvent2.WaitOne(); toRet = currentRespone; return toRet; } void c_OnMessageArrivedEvent( int Id, string root, string guid, int TimeOut, out int ReturnCode ) { if ( !guid.Equals(currentGUID.ToString()) ) { _manualResetEvent2.Set(); ReturnCode = 0; return; } object newMessage; c.FetchMessage(Id, 7, out newMessage); currentRespone = newMessage.ToString(); ReturnCode = 0; _manualResetEvent2.Set(); } } I'm really noob in using waithandle, but my idea was to create an instance that sends the message and waits for an event. As soon as the event arrived, checks if the message is the one I expect (checking the unique guid), otherwise continues to wait for the next event. This because could be (and usually is in this way) a lot of clients working concurrently, and I want them to work parallel. As I implemented my stuff, at the moment if I run client 1, client 2 and client 3, client 2 starts sending message as soon as client 1 has finished, and client 3 as client 2 has finished: not what I'm trying to do. Can you help me to fix my code and get my target? Thanks!

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• A script that writes errors and should create a event-error

  - by helmich

  this if it works should check the internet connection if there is a connection it does nothing. if there isn't a connection it should write a error in a txtfile if that happend 5 times it should create a error but it doesn't I will show you the whole code that i have now and the piece of code that i want in a loop. I can't get it in the way i want. I want it to creat 1 Event-error after 5 times writing to the file. this is the whole code i will put the code i want in a loop under it strDirectory = "Z:\text2" strFile = "\foutmelding.txt" strText = "De connectie is verbroken" strWebsite = "www.helmichbeens.com" If PingSite(strWebsite) Then WScript.Quit 'Website is pingable - no further action required Set objFSO = CreateObject("Scripting.FileSystemObject") RecordSingleEvent Dim fout For fout = 1 To 5 : Do If fout = 5 Then Exit Do Set WshShell = WScript.CreateObject("WScript.Shell") Call WshShell.LogEvent(1, "Test Event") Loop While False : next '------------------------------------ 'Record a single event in a text file '------------------------------------ Sub RecordSingleEvent If Not objFSO.FolderExists(strDirectory) Then objFSO.CreateFolder(strDirectory) Set objTextFile = objFSO.OpenTextFile(strDirectory & strFile, 8, True) objTextFile.WriteLine(Now & strText) objTextFile.Close End sub '---------------- 'Ping my web site '---------------- Function PingSite( myWebsite ) Set objHTTP = CreateObject( "WinHttp.WinHttpRequest.5.1" ) objHTTP.Open "GET", "http://" & myWebsite & "/", False objHTTP.SetRequestHeader "User-Agent", "Mozilla/4.0 (compatible; MyApp 1.0; Windows NT 5.1)" On Error Resume Next objHTTP.Send PingSite = (objHTTP.Status = 200) On Error Goto 0 End Function '----------------------------------------------- 'Counts the number of lines inside the text file '----------------------------------------------- Function EventCount(fout) strData = objFSO.OpenTextFile(strDirectory & strFile,ForReading).ReadAll arrLines = Split(strData,vbCrLf) EventCount = UBound(arrLines) End Function This is the whole code, and it doesnt work correctly becaus it creats a event-log rightaway and it should do that after the script has written 5 times to the textfile here is the code that writes to a textfile Sub RecordSingleEvent If Not objFSO.FolderExists(strDirectory) Then objFSO.CreateFolder(strDirectory) Set objTextFile = objFSO.OpenTextFile(strDirectory & strFile, 8, True) objTextFile.WriteLine(Now & strText) objTextFile.Close End sub and here is the code but this part doesnt not work or atleast i think it is this part Dim fout For fout = 1 To 5 : Do If fout = 5 Then Exit Do Set WshShell = WScript.CreateObject("WScript.Shell") Call WshShell.LogEvent(1, "Test Event") Loop While False : next Function EventCount(fout) strData = objFSO.OpenTextFile(strDirectory & strFile,ForReading).ReadAll arrLines = Split(strData,vbCrLf) EventCount = UBound(arrLines) End Function this is the not working part and I don't know what to do anymore so can you please take a look at it tank you very much. btw: this code can be very usefull for a network administrator

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• C#/.NET Little Wonders: The EventHandler and EventHandler&lt;TEventArgs&gt; delegates

  - by James Michael Hare

  Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. In the last two weeks, we examined the Action family of delegates (and delegates in general), and the Func family of delegates and how they can be used to support generic, reusable algorithms and classes. So this week, we are going to look at a handy pair of delegates that can be used to eliminate the need for defining custom delegates when creating events: the EventHandler and EventHandler<TEventArgs> delegates. Events and delegates Before we begin, let’s quickly consider events in .NET.  According to the MSDN: An event in C# is a way for a class to provide notifications to clients of that class when some interesting thing happens to an object. So, basically, you can create an event in a type so that users of that type can subscribe to notifications of things of interest.  How is this different than some of the delegate programming that we talked about in the last two weeks?  Well, you can think of an event as a special access modifier on a delegate.  Some differences between the two are: Events are a special access case of delegates They behave much like delegates instances inside the type they are declared in, but outside of that type they can only be (un)subscribed to. Events can specify add/remove behavior explicitly If you want to do additional work when someone subscribes or unsubscribes to an event, you can specify the add and remove actions explicitly. Events have access modifiers, but these only specify the access level of those who can (un)subscribe A public event, for example, means anyone can (un)subscribe, but it does not mean that anyone can raise (invoke) the event directly.  Events can only be raised by the type that contains them In contrast, if a delegate is visible, it can be invoked outside of the object (not even in a sub-class!). Events tend to be for notifications only, and should be treated as optional Semantically speaking, events typically don’t perform work on the the class directly, but tend to just notify subscribers when something of note occurs. My basic rule-of-thumb is that if you are just wanting to notify any listeners (who may or may not care) that something has happened, use an event.  However, if you want the caller to provide some function to perform to direct the class about how it should perform work, make it a delegate. Declaring events using custom delegates To declare an event in a type, we simply use the event keyword and specify its delegate type.  For example, let’s say you wanted to create a new TimeOfDayTimer that triggers at a given time of the day (as opposed to on an interval).  We could write something like this: 1: public delegate void TimeOfDayHandler(object source, ElapsedEventArgs e); 2:  3: // A timer that will fire at time of day each day. 4: public class TimeOfDayTimer : IDisposable 5: { 6: // Event that is triggered at time of day. 7: public event TimeOfDayHandler Elapsed; 8:  9: // ... 10: } The first thing to note is that the event is a delegate type, which tells us what types of methods may subscribe to it.  The second thing to note is the signature of the event handler delegate, according to the MSDN: The standard signature of an event handler delegate defines a method that does not return a value, whose first parameter is of type Object and refers to the instance that raises the event, and whose second parameter is derived from type EventArgs and holds the event data. If the event does not generate event data, the second parameter is simply an instance of EventArgs. Otherwise, the second parameter is a custom type derived from EventArgs and supplies any fields or properties needed to hold the event data. So, in a nutshell, the event handler delegates should return void and take two parameters: An object reference to the object that raised the event. An EventArgs (or a subclass of EventArgs) reference to event specific information. Even if your event has no additional information to provide, you are still expected to provide an EventArgs instance.  In this case, feel free to pass the EventArgs.Empty singleton instead of creating new instances of EventArgs (to avoid generating unneeded memory garbage). The EventHandler delegate Because many events have no additional information to pass, and thus do not require custom EventArgs, the signature of the delegates for subscribing to these events is typically: 1: // always takes an object and an EventArgs reference 2: public delegate void EventHandler(object sender, EventArgs e) It would be insane to recreate this delegate for every class that had a basic event with no additional event data, so there already exists a delegate for you called EventHandler that has this very definition!  Feel free to use it to define any events which supply no additional event information: 1: public class Cache 2: { 3: // event that is raised whenever the cache performs a cleanup 4: public event EventHandler OnCleanup; 5:  6: // ... 7: } This will handle any event with the standard EventArgs (no additional information).  But what of events that do need to supply additional information?  Does that mean we’re out of luck for subclasses of EventArgs?  That’s where the generic for of EventHandler comes into play… The generic EventHandler<TEventArgs> delegate Starting with the introduction of generics in .NET 2.0, we have a generic delegate called EventHandler<TEventArgs>.  Its signature is as follows: 1: public delegate void EventHandler<TEventArgs>(object sender, TEventArgs e) 2: where TEventArgs : EventArgs This is similar to EventHandler except it has been made generic to support the more general case.  Thus, it will work for any delegate where the first argument is an object (the sender) and the second argument is a class derived from EventArgs (the event data). For example, let’s say we wanted to create a message receiver, and we wanted it to have a few events such as OnConnected that will tell us when a connection is established (probably with no additional information) and OnMessageReceived that will tell us when a new message arrives (probably with a string for the new message text). So for OnMessageReceived, our MessageReceivedEventArgs might look like this: 1: public sealed class MessageReceivedEventArgs : EventArgs 2: { 3: public string Message { get; set; } 4: } And since OnConnected needs no event argument type defined, our class might look something like this: 1: public class MessageReceiver 2: { 3: // event that is called when the receiver connects with sender 4: public event EventHandler OnConnected; 5:  6: // event that is called when a new message is received. 7: public event EventHandler<MessageReceivedEventArgs> OnMessageReceived; 8:  9: // ... 10: } Notice, nowhere did we have to define a delegate to fit our event definition, the EventHandler and generic EventHandler<TEventArgs> delegates fit almost anything we’d need to do with events. Sidebar: Thread-safety and raising an event When the time comes to raise an event, we should always check to make sure there are subscribers, and then only raise the event if anyone is subscribed.  This is important because if no one is subscribed to the event, then the instance will be null and we will get a NullReferenceException if we attempt to raise the event. 1: // This protects against NullReferenceException... or does it? 2: if (OnMessageReceived != null) 3: { 4: OnMessageReceived(this, new MessageReceivedEventArgs(aMessage)); 5: } The above code seems to handle the null reference if no one is subscribed, but there’s a problem if this is being used in multi-threaded environments.  For example, assume we have thread A which is about to raise the event, and it checks and clears the null check and is about to raise the event.  However, before it can do that thread B unsubscribes to the event, which sets the delegate to null.  Now, when thread A attempts to raise the event, this causes the NullReferenceException that we were hoping to avoid! To counter this, the simplest best-practice method is to copy the event (just a multicast delegate) to a temporary local variable just before we raise it.  Since we are inside the class where this event is being raised, we can copy it to a local variable like this, and it will protect us from multi-threading since multicast delegates are immutable and assignments are atomic: 1: // always make copy of the event multi-cast delegate before checking 2: // for null to avoid race-condition between the null-check and raising it. 3: var handler = OnMessageReceived; 4: 5: if (handler != null) 6: { 7: handler(this, new MessageReceivedEventArgs(aMessage)); 8: } The very slight trade-off is that it’s possible a class may get an event after it unsubscribes in a multi-threaded environment, but this is a small risk and classes should be prepared for this possibility anyway.  For a more detailed discussion on this, check out this excellent Eric Lippert blog post on Events and Races. Summary Generic delegates give us a lot of power to make generic algorithms and classes, and the EventHandler delegate family gives us the flexibility to create events easily, without needing to redefine delegates over and over.  Use them whenever you need to define events with or without specialized EventArgs.   Tweet Technorati Tags: .NET, C#, CSharp, Little Wonders, Generics, Delegates, EventHandler

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• Problems with registering click event listener to a frame-element

  - by distractedBySquirrels

  Hi everybody, I ran into a problem with adding an event listener. I wrote a Firefox plugin a while ago for my bachelor thesis. It was based on a different attacker model than you would normally expect. In this scenario the attacker was the service provider (like Facebook, Google,...), who reads all your private data stored on their site (via JS). My final solution was to temporally allow JS (while the page loads and after an user action occured). To observe the interaction I used event listener, which worked very well so far. But last week I noticed that my approach doesn't work with web sites which are using a frameset (I added the event listener to the body...). So I tried to add the listener to the frameset respectively to the frame. But the clicks are only noticed when you actually click on the frame... (eg resize the frame with your mouse) But I want to register clicks on the document loaded inside the frame. I already tried the .frameElement. Sadly it seems that Firefox doesn't like my (or, which is more likely, I'm too stuipd :) ) and claims there are no frames... Could anyone tell me how to add an event listener to the document inside a frame? The web site looks like this: <html> <head> <title>Frameset Test</title> </head> <frameset cols="150,*"> <frame src="nav.html" name="Navigation"> <frame src="main.html" name="Main"> </frameset> </html> This was my first bigger projekt with Mozilla so this could be a really dumb failure of mine... I hope you guys can help me. Thanks in advance. Sebastian

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• jQuery problem with change event and IE8

  - by Marcus

  There is a bug in jQuery 1.4.2 that makes change event on select-element getting fired twice when using both DOM-event and a jQuery event, and this only on IE7/8. Here is the test code: <html> <head> <script src="http://code.jquery.com/jquery-1.4.2.js" type="text/javascript"></script> <script type="text/javascript"> jQuery(document).ready(function() { jQuery(".myDropDown").change(function() { }); }); </script> </head> <body> <select class="myDropDown" onchange="alert('hello');"> <option>1</option> <option>2</option> <option>3</option> <option>4</option> </select> </body> </html> Ticket to actual bug: http://dev.jquery.com/ticket/6593 This causes alot of trouble for us in our application cause we use both ASP.NET-events mixed with jQuery and once you hook up a change event on any element every select (dropdown) gets this double firing problem. Is there anyone who knows a way around this in the meantime until this issue is fixed?

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• flash as3 document class and event listeners

  - by Lee

  I think i have this document class concept entirly wrong now, i was wondering if someone mind explaining it.. I assumed that the above class would be instantiated within the first frame on scene one of a movie. I also assumed that when changing scenes the state of the class would remain constant so any event listeners would still be running.. Scene 1: I have a movieclip named ui_mc, that has a button in for muting sound. Scene 2: I have the same movie clip with the same button. Now the eventListener picks it up in the first scene, however it does not in the second. I am wondering for every scene do the event listeners need to be resetup? If that is the case if their an event listener to listen for the change in scene, so i can set them back up again lol.. Thanks in advance.. package { import flash.display.MovieClip; import flash.events.MouseEvent; import flash.media.Sound; import flash.media.SoundChannel; public class game extends MovieClip { public var snd_state:Boolean = true; public function game() { ui_setup(); } public function ui_setup():void { ui_mc.toggleMute_mc.addEventListener(MouseEvent.CLICK, snd_toggle); } private function snd_toggle(event:MouseEvent):void { // 0 = No Sound, 1 = Full Sound trace("Toggle"); } } }

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• Asynchronous event loop design and issues.

  - by Artyom

  Hello, I'm designing event loop for asynchronous socket IO using epoll/devpoll/kqueue/poll/select (including windows-select). I have two options of performing, IO operation: Non-blocking mode, poll on EAGAIN Set socket to non-blocking mode. Read/Write to socket. If operation succeeds, post completion notification to event loop. If I get EAGAIN, add socket to "select list" and poll socket. Polling mode: poll and then execute Add socket to select list and poll it. Wait for notification that it is readable writable read/write Post completion notification to event loop of sucseeds To me it looks like first would require less system calls when using in normal mode, especially for writing to socket (buffers are quite big). Also it looks like that it would be possible to reduce the overhead over number of "select" executions, especially it is nice when you do not have something that scales well as epoll/devpoll/kqueue. Questions: Are there any advantages of the second approach? Are there any portability issues with non-blocking operations on sockets/file descriptors over numerous operating systems: Linux, FreeBSD, Solaris, MacOSX, Windows. Notes: Please do not suggest using existing event-loop/socket-api implementations

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