How To Add Event Handler To Local Variable
Apr 25, 2012
I have a form in VB.NET that is used as a dialog in a mainform. Its instances are always locally defined, there's no field for it. When the user clicks the OK button in the dialog, it will fire an event with exactly one argument, an instance of one of my classes. Since it is always a local variable, how can I add an event handler for that event?
Code for the event, a field in MyDialog:
public Event ObjectCreated(ByRef newMyObject as MyObject)
Code for the main form to call dialog : (never mind the syntax)
Dim dialog As New MyDialog()
dialog.ShowDialog(Me)
AddHandler ObjectCreated, (what do I put here?) //Or how do I add a handler?
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Apr 27, 2009
Im making a site in Visual Studio using vb and I have a variable in page_load but need its value in the event handler of a button for passing on session.
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Apr 22, 2010
On one side, in Vb.Net when you add an event handler to an object the created method is named: <NameOfTheObject>_<NameOfTheMethod>.As I like to have consistent syntax I always follow this rule when creating event handlers by hand.On the other side when I create private variables I prefix them with m_ as this is a common thing used by the community, in C# people use to put _ at the beginning of a variable but this is no CLS compliant.
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Apr 18, 2011
The event handlers in my parent class are never called though the events are raised in the child class.
The Code:
Public Class childForm
Public Event checkboxchangedEvent(ByVal checkbox1 As Boolean, ByVal checkbox2 As Boolean)
Private Sub checkboxchanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CheckBox1.CheckedChanged, CheckBox2.CheckedChanged
[code]....
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Aug 27, 2011
How do I get a Event Handler to fire from within a nother Event Handler?
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Mar 21, 2012
remove an event handler from within the event handler?
I have a class that gets data from a hand scanner. When the scan is complete and the data is validated, the class fires a custom "ScanComplete" event and returns the data in a custom EventArgs.
In the calling program, I'm creating an instance of the scanning class and adding a handler for the "ScanComplete" event. In the event handler I get the data that was scanned and then remove the handler.
It seems to be working but it feels wrong to remove the handler while I'm running inside the handler. Will this cause a problem?
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Nov 27, 2010
I'm trying to complete this airline reservation application, but having a problem in this part of the question:Creat an event handler for the FlightBindingSource's PositionChanged event: select FlightBindingSource in the class Name combobox then select position changed in method name combobox to creat the FlightBindingSource's PositionChanged event handler. Write a code to access the currently displayed flight object and pass its flightNumber to method DisplayPassengers as a decimal.This Is my code so far:
HTML
Public Class AirlineReservationForm
Private database As New ReservationsDataClassesDataContext()
Private Sub FillAll()[code].....
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Oct 20, 2009
Below I create an array of labels. I would like to add an click event to my labels. Can someone point me in a direction?
[Code]...
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Sep 24, 2010
When I utilize AddHandler in VB to add my own method to the Click event :
AddHandler Button.Click, AddressOf myButton_Click
I see that my code executes last - after other event handlers for the Button_Click event. Is there a way to insert my event handler in front of other events so that it executes first?
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May 28, 2012
I am planning to use a shared variable to implement a logging facility. Have a look at the code below:
Imports System.IO
Public Class TestClass
Public Shared objError As New StreamWriter("C:Test.txt")
End Class
[Code]....
I think I have found my answer here: [URL] "A static variable continues to exist and retains its most recent value. The next time your code calls the procedure, the variable is not reinitialized, and it still holds the latest value that you assigned to it. A static variable continues to exist for the lifetime of the class or module that it is defined in."
I am not convinced that this is the best way to create a logging facility.
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Jan 14, 2009
When I've used the remove handler method in my code, I get this warning:The 'AddressOf' expression has no effect in this context because the method argument to 'AddressOf' requires a relaxed conversion to the delegate type of the event. Assign the 'AddressOf' expression to a variable, and use the variable to add or remove the method as the handler.Why do I have to assign the "AddressOf" expression to a variable?
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Jul 30, 2011
Is it possible to determine using VB.NET whether a certain event has any handlers attached to it? I don't own the event, in this particular case I want to know which of the items in a Windows.Forms.MenuStrip have their ToolstripMenuItem.Click event handled.
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Apr 1, 2012
I've been looking for a solution to this for several hours now and cannot find a solution.
The Scenario:I have a masterpage baseclass (called basemaster)All of my master pages inherit from basemaster
basemaster defines an event 'Public Event HandleClickEvent As EventHandler'I have a masterpage named master1
master1 defines an event handler 'Public Shadows Event HandleClickEvent As EventHandler'master1 has a user control named usr1 usr1 has a button that raises event ButtonClicked when clicked I have a page (thePage) that uses master1 thePage has a button click event handler that it registers like so: 'AddHandler Master.HandleClickEvent, AddressOf HandleTheClick' master1 has code something like:
Protected Sub Usr1_ButtonClicked(ByVal sender As Object, ByVal e As System.EventArgs) Handles Usr1.ButtonClicked RaiseEvent HandleClickEvent(sender, e) End Sub when thePage loads I see it register the handler on master1 when the button is clicked, Usr1_ButtonClicked is fired and I step through the RaiseEvent but HandleClickEvent on thePage is never reached.
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Jan 12, 2012
This code is part of AjaxControlToolkitSampleSite. To be exact, it is in the AsyncFileUpload control[code]...
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Feb 12, 2011
how to add one event handler name clearallboxes that handles the TextChanged event for both examples(Customer text box and Total text box ) This event handler should clear the values in the text boxes that display the results.
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Jun 9, 2011
i have a page which dynanically create a link when it load, after i click on the link it should loop in the database fetch all the record and display another set of link , then when i click on these link it should give me all information about this particular record it like this one
Q: when the page loads, it creates the first link which is associated with an event handler, it fire the first event handler (Getname) but it not firing the second event handler (GetnameDetails)
Protected Sub Page_Init(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Init
If ViewState.Item("nameload") IsNot Nothing Then
If ViewState.Item("nameload").ToString = "True" Then
[Code]....
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May 19, 2011
I have a form that is derived from a base class. When the form is created a behavior class is also generated that handles event management, bindings, etc...I create a form instance(FormFoo). When the associated behavior class is created it has a method in it with a signature of: grid_EventA(....) Handles grid.eventA
I want to handle EventA in FormFoo instead of the behavior class so I remove the handler that was generated in the behavior class and add a handler that points to a method in FormFoo. This all works just peachy. The event is properly handled in FormFoo only.
Next I instantiate a modal form(FormBar) via a button click in FormFoo. I then close FormBar. Now we have a problem.When eventA fires it is now handled from the Event handler in FormFoo AND in the behavior class associated with form foo(bad).Is the event handler in the behavior class(grid_EventA(....) Handles grid.eventA) getting resubscribed when the form gets focus again? I don't understand how that event is getting resubscribed.
I figured it out I removed the Handles grid.EventA from the method signature:
grid_EventA(....) Handles grid.eventA
Then I added the handler during initialization of the BehaviorClass using:
AddHandler grid.EventA, AddressOf grid_EventA
Once I did that the problem went away. It appears that when you use MethodName(..) Handles that the event bindings get reset when the control comes back into focus.
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Jun 1, 2010
In C# I can test for this...
public event EventHandler Trigger;
protected void OnTrigger(EventArgs e)
{
[Code]....
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."
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Dec 15, 2011
I am trying to convert this code written in C# to VB:[code]This is what I have currently, but it always throws an error when I run it:[code]
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Jul 5, 2010
At the beginning of a VB .NET function I remove an event handler and add it again at the end of the function because the function's code would trigger those events and I do not want them to trigger for the duration of the function. This usually works, but I have run into a few situations where the event still gets called even though I have already removed it. Sometimes removing it twice at the beginning of the function fixes it, but other times no matter how many times I remove it, it still fires.
Edit:The code is in a Form that has a virtual mode datagridview. I want to run some operations that will trigger the CellValueNeeded event for the datagridview without that event being fired (because it will interfere).
Public Sub DoEventRaisingStuff()
RemoveHandler grid.CellValueNeeded, AddressOf grid_CellValueNeeded
'Do things that would trigger CellValueNeeded
AddHandler grid.CellValueNeeded, AddressOf grid_CellValueNeeded
End Sub
Removing the handler multiple times does not prevent the event from firing, so it doesn't seem to be added multiple times somewhere else by accident.Is there a way to find out what event handlers are active?
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Dec 19, 2006
I'd like to know how to attach an event handler in VB,There is a C# sample code in this URL that I want to convert to VB (Figure 8)
http://msdn.microsoft.com/msdnmag/issues/06/01/speechinWindowsVista/default.aspx?loc=&fig=true#fig8
I have succesfully converted every lines to VB except those :
[code].....
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Nov 26, 2010
I have a chart Component that was rendering based on my menu selection(say Sales data, Purchase data), I have two different class to render this, In main form i have a chart control(which was referenced by my appropriate class), When I choose "sales" both sales and purchase chart rendering event handler called, how to solve this?
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Mar 4, 2010
Why can't I get the clickedItem.SelectedItems.Item(0).Text value?
Dim UserList As New ListView()
AddHandler UserList.MouseDown, AddressOf ToolSearchAD_ListView_Click
UserList.ContextMenuStrip = c_mnuADSearch
[code].....
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Feb 23, 2011
I have a VB6 app that works correctly in win7.
I downloaded and installed VS2010 yesterday, and converted the app to VB2010.
The app works correctly except for one problem. I have a label array which has two event handlers defined, one for a double click and one for mouse down.
A double click is ignored and the mouse down event is raised. It shows the left button was clicked once.
If I comment out the mouse down handler, the double click event is raised and it shows left button was clicked twice.
What i want to accomplish is allow a user to double click an array element on the screen which then saves the number associated with that element and then click somewhere else to copy the data or alternatively, drag and drop the element to the new location.
The drag operation on the source element always triggers a mouse down, but so does the first of the two clicks in a double click.
It seems that none of the other newer events are raised, eg GiveFeedbackEvent, QueryContinueDrag, DragOver, etc.
So, how do I trap a double click and a drag start without using the mousedown event for the dragstart?
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Dec 5, 2011
Is there a method for doing this in VB.NET. I have what I need, but in C#, I have no idea on how to do this with VB.NET.
[code]...
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May 3, 2010
I never used Public Event, but now I have this line:
Code:
This SHOULD be a "trigger" when something in the event log happens.
Now I have 2 questions:
How do I work with public event? In other words, if I write something like this:
Code:
Is it right?
Last question:
Is there any other way to check event log? I found this: [url]
But is a service, I'm writing an application.
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Jan 18, 2012
I converted some code from c# to vb, I have the following error:-
m_axCalendar.DoRetrieveDayEvents += New AxXtremeCalendarControl._DCalendarControlEvents_DoRetrieveDayEventsEventHandler(m_axCalendar_DoRetrieveDayEvents)
Red Error = Error1'Public Event DoRetrieveDayEvents(sender As Object, e As AxXtremeCalendarControl._DCalendarControlEvents_DoRetrieveDayEventsEvent)' is an event, and cannot be called directly. Use a
[code]....
I can get rid of Blue error by changing it to : AddressOf m_axCalendar_DoRetrieveDayEvents Not sure how to fix red error?
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Dec 21, 2009
I want to handle the event "Smallincrement in vb.net 2005 " I am studying through the book BlackBook of VB.nET 2003.
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Apr 11, 2011
While being in a base class, I want to remove a base class's object's event that is bound to a function in the child class. A little more detail is, there is a grid control declared in the base class, this grid has a rowselected event which the child class catches. Now staying in the base class I have the access to the grid control object and I want to remove the event handler that is catching its rowselected event and instead bind it to my own eventhandler (inside the base class).
I have been trying this code, its just a simulation of the original code so that things remain simple:
Imports System
Imports System.Reflection
Module Module1
[Code].....
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May 4, 2011
I have a two windows forms classes, a base class and a derived class. The base class has an event handler which handles ValueChanged on some component. I have also written a different event handler for the same event on the derived class.
When I create an instance of the derived class and fire the event, I find that both event handlers run (the base class one and then the derived class one). But I want only the handler in the derived class to run.
Edit: Here is what the code looks like (can't post the actual code):
Public Class BaseForm
Inherits System.Windows.Forms.UserControl
(Windows Form Designer Generated Code)
[Code].....
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