Events - .NET: WithEvents Not Working?
Apr 21, 2010
I have the following classes: Public Class Email
[Code]...
If a create a wrong email lets say "email" the exception is correctly cached and a message is showed however is i input a valid email the event is not raised, the object is being created but no message is shown and no error or exception is thrown i suspect it has something to do with using "myemail = new Email(email)" but i have seen examples of using new with withevents with no problem.
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Jan 23, 2012
listbox control (lst_tpAccount_AvailableAccounts) has an event handler:
Private Sub lst_tpAccount_AvailableAccounts_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles lst_tpAccount_AvailableAccounts.SelectedIndexChanged
[code].....
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Sep 27, 2010
I have a Child class which uses DataContractSerialization and raises a Changed event when its Name property is set.
<DataContract()>
Public Class Child
Public Event Changed()
The Parent class is serialzed and deserialized and all the data (including the Child) is saved and resored as expected.However, after deserialization, the Changed event is never raised!I know the deserialization process bypasses class constructors, but shouldn't the event be initialized?Is it possible to serialize/deserialize the Event?Is there a way to initialize the event in the OnDeserialzed method of the Child rather than the Parent (see below)?
(1) Add a constructor to the Child class which takes an instance of itself as an argument.
(2) Add an OnDeserialized method to the Parent class which creates a New instance of the Child class based on the deserialzed instance of the Child class.
<OnDeserialized()>
Private Sub OnDeserializedMethod(ByVal Context As StreamingContext)
Child = New Child(Child)
End Sub
Now the Changed event is raised as expected.
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Jun 23, 2009
I am working on a project which will be installed in Embedded pc which won't have mouse and keyboard. Works with touch screen. I have an option in my software to make calls.I need to have an option like Push to talk. When need to talk they need to push the button and when they release they can't talk. Something like walkie talkie concept. The embedded pc where my software will be installed will have touch screen. How can I do this??
I tried to write my code in button click event and when they take out the mouse from the button, I am stopping voice. But, that is not I want. I need to push to talk and release after talk.
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Apr 18, 2011
I want to use the following snippit.
For Each x As Control In Me.Controls
If TypeOf x Is CustomControl Then
SomeAction( x.CustomEventofCustomControl)
End If
Next
The problem here is that not all controls have event CustomEventofCustomControl, so the complier shrieks. How do I get around this.
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Mar 15, 2012
I believe I may have already posted a much longer explanation of this , but its driving me spare!!! I have several pieces of code that click buttons thru sendmessage commands, all the code works fine in Windows 7! But I put the app on WindowsXP and only some of the buttons will work,
[Code]...
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Apr 5, 2010
Here is a simple class I coded inheriting SimpleShape in VBPower Packs. The events are not firing. What might be the reason? I checked the property "CanRaiseEvents" and it says "True"
[Code]...
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May 12, 2009
I am trying to use the keydown/keyup events with buttons in the same project and it not working properly. I have 4 red boxes and when I press an arrow key the box should change to green according to which arrow key it corrosponds to. I have this part working fine, however only when there is nothing else in the project. When I add in say 3 buttons, Button1, Button2, Button3 and try runing the program instead of the correct red box changing to green, button outline just moves between buttons 1,2 and 3. I have tried turning tabstop off for the three buttons but that didnt work. how to read the keydown/keyup while still having buttions that can be pressed with a mouse?
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Dec 17, 2009
Who knows, why in vb.net WinForm projects the designer by default use the Friend WithEvents attributes and in C# - private ones.
By ex, in a form.designer.
.cs
private Label Label1;
.vb
Friend WithEvents Label1 as Label;
For WithEvents is more or less clear(for using Handles, apparently). But why Friend in VB and private in C#...
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Jul 11, 2011
i have the folowing co
For x = 0 To 7 Step 1
For i = 0 To 7 Step 1
Dim rectangleShape1 As New Microsoft.VisualBasic.PowerPacks.RectangleShape() 'create a new object to assign to the array location
board(x, i) = New Microsoft.VisualBasic.PowerPacks.RectangleShape() 'create the new object in the array
[code].....
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Feb 11, 2010
When you declare an object 'WithEvents' and then utilize the "Handles" clause at the end of your event methods, how does Visual Basic manage a reference change for the object? In other words, if the withevents var is set to ObjectA, then later I switch it to ObjectB (or nothing), does Visual Basic automatically both remove those handler methods from ObjectA, and attach them to ObjectB? Or do I still have a ObjectA's events being handled behind the scenes?
I ask this because if instead you use AddHandler for an object, and then switch your reference, unless you removed the handler before switching, your original object is still handled (at least I'm pretty sure that's how it works).
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May 17, 2010
Does anyone know why a local variable cannot be declared WithEvents?T
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Jun 9, 2011
I'm trying to create multiple instances of a child form. This form has an event that feeds a string variable back to the parent so I'm declaring it with WithEvents which is declared outside of the Sub - meaning multiple clicks will not open multiple forms.
another method of doing this while keeping the event?:
Dim WithEvents FRestoreDB As New FormRestoreDB()
Private Sub BtnOpenDB_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnOpenDB.Click
[Code].....
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Feb 24, 2010
Is it necessary to set to Nothing(in Dispose()) all WithEvents fields?
Apparently Handles keyword adds handlers to such fields, but does not remove it until this field is not Nothing, and this can generate memory leaks?!.
This should be specially actual on cases like
class Foo
{
Private WithEvents _bar as Bar
[Code].....
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Feb 24, 2010
Protected WithEvents gel As New TabPage
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
TabControl1.TabPages.Add(gel)
gel.Text = ("Gel")
Private Sub Gel_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles gel.Click
MsgBox("test") So my problem is that if I click on the tabpage gel, nothing happens.
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Sep 7, 2011
I have an application that performs a lot of busy work. All of the work is performed using a BackgroundWorker and the point of execution is the DoWork Event of the BackgroundWorker.On the UI thread, before the workload begins, I display a PictureBox that contains an animated GIF that illustrates progress; for the most part this works fine and the UI thread is not paused or slowed while the BackgroundWorker does its job. There is however, one instance where the UI thread is impacted by the work being done and it defeats the whole purpose of putting this work in a separate thread. In this application, the user must wait until the work completes before they can move to the next step, so my sole reason for moving this all to a BackgroundWorker was so that I could display a smooth, uninterrupted progress indicator on the UI thread while this work was being done, so that the user could see that something was happening.
The case where the work being done is impacting the UI thread (pausing/delaying the PictureBox animation) deals with a referenced COM object.
[Code]...
All of the COM object event handlers and subsequent functions are appropriately using Delegates, but I am not sure why the ProcessFiles method would cause the UI thread to hang while the work completes; I thought that was the whole purpose of the BackgroundWorker.
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Dec 14, 2010
I'd like to create an array of objects with events. Where do I need to put the "WithEvents"? Should it be placed in the ReDim line or the next one?I'm trying to use a "global" event, like objects of people that recieve a time-event to get older.
[Code]...
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Oct 13, 2011
I have been trying to implement the jQuery weekcalendar using .net. What I can't seem to figure out is why weekcalendar states events.events is undefined after I make an ajax call to a webmethod I created which returns JSON. Below is the relevant code:
[Code]...
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Aug 2, 2009
I want to make Keybord events and mouse events for learning and educational Purpose.
1. In Form any object like A "picture box" move by Arrow keys .
2. Picture Box Contain many Picture i want change Picture With next and Previos By Arrow keys.
3. I contain Voice of alphabet in Mp3.When i Press any button in textbox then its work.
4. Mouse Pointer Change My Own.
5. I click any Object or any thing By mouse its noice clicking sound like Tik Tik Tik.... Question No 3 is very hard to do . but not im possible
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Mar 5, 2010
What is the optimal approach to a WithEvents Collection - VB.NET?Have you any remarks on the code bellow (skipping the Nothing verifications)?The problem is when I obtain the LinkedListNode(Of Foo) in a For Each block I can set myNode.Value = something, and here is a handlers leak...
-Could I override the FooCollection's GetEnumerator in this case?
-No. :( cause NotInheritable Class LinkedListNode(Of T)
Class Foo
[code]....
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Oct 15, 2010
The vb.net "WithEvents" syntax is very useful, but if a WithEvents field which references a long-lived object is not nulled out, it will often constitute a memory leak.Is there any easy way for a Dispose routine to have vb.net automatically clear out all WithEvents fields and unsubscribe them?
I've figured out a nice way to wrap the creation of disposable fields so that they will be automatically Disposed when the containing object is disposed, without having to individually list such objects. Is there any way to take care of WithEvents fields without having to manually null them out in the Dispose routine?
EDIT:Since there was no response indicating a built-in way to do it without reflection, is there any built-in means of using reflection to determine whether a particular property is a VB automatic implementation of a WithEvents "field"? I know that a WithEvents "field" called "foo" is implemented as a property called "foo" and a field called "_foo", but that's such a common naming pattern that I wouldn't count on it. Is there some attribute that could be used to determine which properties need to be auto-nulled?
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May 9, 2009
Public WithEvents Tree as Tree. I am not able to Serialize the Tree class, but if i remove the "WithEvents" keyword, it works fine. Why? What should I do if I have to declare it with "WithEvents"?
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Sep 27, 2009
I have done an extensive search before posting this question, using many different search parameters without success at finding an answer.Using Visual Studio 2008 Express VB:My program requires a notification when a wav file has finished playing, a media player song list will not suit my needs.I have used System.Media.SoundPlayer, Microsoft.DirectX.DirectSound and My.Computer.Audio.Play to play a wav file. All work well at playing and stopping the requested wav. So far, I have not found a methode to capture an event when the wav has ended. DirectSound stops playing when the form has lost focus, so I dont think that I can use it. Audio.Play AudioPlayMode.WaitToComplete only holds up other operations and I dont want to create multiple threads.
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May 13, 2011
Can you raise events from a class that has only shared members and doesn't get instantiated? I originally had the class members non-shared and created instances of the class where I need them. I had the events being raised and everything worked as expected. But as the class members are actually application level and do not need instancing, I converted all members in the class to shared so they could be accessed from anywhere in the program without creating an instance of the class. But WithEvents requires the creation of a class instance. I've done that and it seems to work fine when using an instance. And since I need the events handled in only one class, I can create the instance in that class and let all other areas access the class directly, without creating an instance.
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May 3, 2011
So I wanted everyone's opinion on this and what you think of this. Using the WithEvents modifier makes life very easy in VB.Net (srsly, I love it), and I was exploring some of its limitations and noticed you can do something along the lines of this:
[Code]....
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Aug 2, 2009
I have to create multiple child window each embedded with dsoframer activex control,
Like,the following,
Private Function add_activex_control()
...
[code]......
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Feb 5, 2010
Is WithEvents & Handles usage preferable to RemoveHandler & AddHandler?
From Memory point of view (remove an added handler after utilization, etc.)
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Aug 24, 2009
I need instructions on how to install a 'WithEvents' into a sqlsever web form, read Server Error message:Description:An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately.Compiler Error Message: BC30506: Handles clause requires a WithEvents variable defined in the containing type or one of its base types.
[code]....
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May 12, 2011
I must say personally, the WithEvents system is, shall we say, open to extreme false sense of security, so to speak. I like a lot of automation in my code, and tend to provide ways to do things manually, with a "default" behavior encoded. However, as I have just discovered, the withevents doesn't HOOK the event delegate until after creation. So even when you do New MyObject(), if an event is triggered during the Sub New() process, the delegate hasn't been assigned yet, and thus the event (which in my current situation is extremely important) never triggers. which begs the question the point of the WithEvents other than removing "AddHandler" lines from procedural code. Sure it saves on typing, due to code completion, but if that's it, that isn't much of a benefit. One would think that using the WithEvents would allow me to do:
PUblic Sub New()
MyBase.New()
RaiseEvent MyEvent()
End Sub
Tragically, this does NOT work, which royally screws up my lazy loading techniques and other such tricks that were supposed to make my code simpler to use, and instead has made things 10 times more complex, as I have to specifically alter class initialization sequences to be outside of class instantiation. (which should be one in the same, imho).Jaeden "Sifo Dyas" al'Raec Ruiner
"Never Trust a computer. Your brain is smarter than any micro-chip."
PS - Don't mark answers on other people's questions. There are such things as Vacations and Holidays which may reduce timely activity, and until the person asking the question can test your answer, it is not correct just because you think it is. Marking it correct for them often stops other people from even reading the question and possibly providing the real "correct" answer.
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Mar 14, 2012
i'm a .net programmer, using .net framework 4, and i have a question about WithEvents clause. [code] Private Sub mylist_AddingNew(ByVal sender As Object, ByVal e As AddingNewEventArgs) Handles mylist.AddingNew..i get this error: Handles clause requires a WithEvents variable defined in the containing type or one of its base types.I think the problem is my custom bindinglist class....but how can i solve this?
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