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  • Is there a way to know in VB.NET if a handler has been registered for an event?

    - by Seth Spearman
    In C# I can test for this... public event EventHandler Trigger; protected void OnTrigger(EventArgs e) { if (Trigger != null) Trigger(this, e); } Is there a way to do this in VB.NET? Test for null I mean? MORE INFO I forgot to mention. I have classes written in C# but I am writing my unit tests in VB.NET. I am trying this in the unit test... If myObject.Trigger IsNot Nothing Then 'do something End If This is causing a compile time error which says ... "Public Event Trigger is an Event and cannot be called directly. Use the RaiseEvent statement to raise an event." Seth

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  • How to pass an event to a method and then subscribe to it?

    - by Ryan Peschel
    Event Handler public void DeliverEvent(object sender, EventArgs e) { } #1: This Works public void StartListening(Button source) { source.Click += DeliverEvent; } #2: And so does this.. public void StartListening(EventHandler eventHandler) { eventHandler += DeliverEvent; } But in #2, you cannot call the method because if you try something like this: StartListening(button.Click); You get this error: The event 'System.Windows.Forms.Control.Click' can only appear on the left hand side of += or -= Is there any way around that error? I want to be able to pass the event and not the object housing the event to the StartListening method.

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  • What is the most efficient way to store a mapping "key -> event stream"?

    - by jkff
    Suppose there are ~10,000's of keys, where each key corresponds to a stream of events. I'd like to support the following operations: push(key, timestamp, event) - pushes event to the event queue for key, marked with the given timestamp. It is guaranteed that event timestamps for a particular key are pushed in sorted or almost sorted order. tail(key, timestamp) - get all events for key since the given timestamp. Usually the timestamp requests for a given key are almost monotonically increasing, almost synchronously with pushes for the same key. This stuff has to be persistent (although it is not absolutely necessary to persist pushes immediately and to keep tails with pushes strictly in sync), so I'm going to use some kind of database. What is the optimal kind of database structure for this task? Would it be better to use a relational database, a key-value storage, or something else?

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  • unable to set fields of a collection-property elements after changing their order (elements becoming

    - by Jaroslav Záruba
    Hello I want to change order of objects in a collection, and then to access+modify fields of those items. Unfortunately the items somehow become 'deleted'. This is what I do... if(someCondition) { MainEvent mainEvent = pm.getObjectById(MainEvent.class, mainEventKey); /* * events in the original order * MainEvent.subEvents field is not in default fetch group, * therefore I also tried to add the named group into the * persistenceManeger fetch plan, no difference * (mainEvent is not instance of the Event sub/class BTW) */ List<Event> subEvents = mainEvent.getSubEvents(); // re-arrange the events according to keysOrdered { Map<Key, Event> eventMap = new HashMap<Key, Event>(); for(Event event : subEvents) eventMap.put(event.getKey(), event); List<Event> eventsOrdered = new LinkedList<Event>(); for(Key eventKey : keysOrdered) eventsOrdered.add(eventMap.put(eventKey, eventMap.get(eventKey))); // } // put the re-arranged items back into the collection property { subEvents.clear(); subEvents.addAll(eventsOrdered); // } pm.makePersistent(mainEvent); eventsOrdered = subEvents; } else eventsOrdered = getEventsUsingAlternateApproach(); /* * so by now the mainEvent variable does not exist; * could it be this lead the persistence manager to mark * my events as abandoned/obsolete/invalid/deleted...? */ for(Event event : eventsOrdered) event.setDate(new Date()); // -> "Cannot write fields to a deleted object" What am I doing wrong please?

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  • SQL to display an event on start date, end date and any days in between.

    - by Tim
    Hello, This should be fairly simple, but I can't get my head around it. I have an event in my database with a startDate and an endDate. I need to display this event (based on the current date) on every day the event occurs. So if the event starts on the 3rd of May and finishes on the 7th of May, the SQL query must find it on every single day. How can I achieve this? SELECT * FROM events WHERE startDate ??? Thanks, Tim

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  • VS/C#: Can I be notified of every event that gets handled while debugging?

    - by Daniel I-S
    I am currently troubleshooting a large and unwieldy GUI-based tool in Visual Studio, and was wondering whether there is any way to get some kind of notification (either by writing to the console or through a third-party tool) whenever any handled event occurs. This would make it a lot easier to track down what precisely is going on while I am interacting with this beast. Is there an 'on any event being handled' event I can handle, or some kind of add-in for VS which would make this possible?

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  • How do I wait for a C# event to be raised?

    - by Evan Barkley
    I have a Sender class that sends a Message on a IChannel: public class MessageEventArgs : EventArgs { public Message Message { get; private set; } public MessageEventArgs(Message m) { Message = m; } } public interface IChannel { public event EventHandler<MessageEventArgs> MessageReceived; void Send(Message m); } public class Sender { public const int MaxWaitInMs = 5000; private IChannel _c = ...; public Message Send(Message m) { _c.Send(m); // wait for MaxWaitInMs to get an event from _c.MessageReceived // return the message or null if no message was received in response } } When we send messages, the IChannel sometimes gives a response depending on what kind of Message was sent by raising the MessageReceived event. The event arguments contain the message of interest. I want Sender.Send() method to wait for a short time to see if this event is raised. If so, I'll return its MessageEventArgs.Message property. If not, I return a null Message. How can I wait in this way? I'd prefer not to have do the threading legwork with ManualResetEvents and such, so sticking to regular events would be optimal for me.

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  • How to get width of button in DateTimePicker-Control/Controls in general?

    - by Inno
    Hello everybody, I implemented a custom DateTimePicker. On the DateTimePicker there is a button. In the examples I've found it's width is set to 16. This is working but I would like to have a dynamic approach. So, is there a way to get the size of this button or is there a general way to get information about .Net-Control sub elements like size etc.? Trying DateTimePicker.Controls didn't help me (it's empty).

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  • Is it possible to remove all event handlers of a given element in javascript?

    - by MartyIX
    Hi, I would like to remove ALL handlers for a given event type. Let's say I've added twice "onclick event" to a button and now I would like to return back to the original state where no event handler was set to the button. How can I do that? P.S.: I've found removeEventListener (non-IE)/detachEvent (IE) methods but the functions want me to pass as a parameter the function that handles the event which seems to me quite clumsy because I would have to store the functions somewhere. EDIT: http://ejohn.org/blog/flexible-javascript-events/ - I'm now using this code Thank you!

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  • Can I reverse the order of a multicast delegate event?

    - by Neil Barnwell
    When you subscribe to an event in .NET, the subscription is added to a multicast delegate. When the event is fired, the delegates are called in the order they were subscribed. I'd like to override the subscription somehow, so that the subscriptions are actually fired in the reverse order. Can this be done, and how? I think something like this might be what I need?: public event MyReversedEvent { add { /* magic! */ } remove { /* magic! */ } }

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  • which is better in general, map or vector in c++?

    - by tsubasa
    As I know that accessing an element in vector takes constant time while in map takes logarithmic time. However, storing a map takes less memory than storing a vector. Therefore, I want to ask which one is better in general? I'm considering using one of those two in my program, which has about 1000 elements. I plan to use 3 dimensional vector, which would take 1000x1000x1000 elements.

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  • [Raise|Trigger|Fire|...] an event?!?

    - by winSharp93
    Hello, in a German programming forum we currently have a discussion about events and what you (grammatically) do with them. The MSDN talks about "Event Raising" and "to raise an event". Thus, this seems to be one possibility. Are there any other synonyms? What about "to trigger an event" and "to fire an event"? A Google search will bring results for all of the three possibilities. This, however, does not mean that they are correct, too, of course. Are they? Are there any (stylistic, ...) differences or are they used in different contexts? Many thanks in advance for ending a heated debate :-)

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  • Binding Javascript Event Handlers to a an Ajax HTML Response?

    - by John
    Let's say I have the following HTML code <div id="outer"> <div id="inner">Hello World</div> </div> At the end of my HTML page, I use javascript to attach event handlers like so, document.getElementById('inner').onclick = function() {alert(this.innerHTML);} document.getElementById('outer').onclick = function() { /* An Ajax Call where the response, which will be a string of HTML content, then goes into document.getElementById('outer').innerHTML */ document.getElementById('inner').onclick = function() {alert(this.innerHTML);} } In the above code, I am expecting <div id="inner">Hello World 2</div> to come back which requires me to re-attach the onclick event handler. This makes sense because the new response coming back is just a string, and I have to tell the browser that after converting to DOM, i also need some event handlers So my question is, is there a better way to manage event handlers on AJAX response that contains HTML content? I could use inline javascript within the html response, but then it prevents me from achieving non-intrusive javascript. So is there a way to achieve non-intrusive javascript and an efficient way to "maintain" event handlers of ajax html responses?

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