Dynamically Add / Remove Event Handler?
Nov 23, 2010
I have a TableGridLayout (6 x 6) which host 36 buttons created at design time.From the 36 buttons, only a handfull maybe needed at anyone time depending on data retrieved from an SQL database.Everytime I need to 'clear' the grid to populate with new items, I clear the text of each button, make it visable if required and then upadate with the new text.On every pass if a button becomes active, I add an event handler to the button like this.[code]...
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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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Mar 4, 2012
I would like to ask a question with DataGridView event handling.The event I am going to handle is the double-clicking of a cell in a DataGridView:If the DataGridView's are statically drawn on the form at design time, then it is easy to assign to each of them an even handler by double clicking the corresponding event in the properties panel.
Private
SubDataGridView1_CellDoubleClick(sender
AsSystem.Object,
[code]....
So basically I have handle to all of the DataGridView's. Is there a way to create a common event handler on this basis?
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Jan 24, 2012
I am passing some values from a Gridview Update Click event to a popup ASP.net page that dynamically builds a series of textboxes in a Placeholder based on the number of sentences that are found in a specific cell of the Grid Row selected.The boxes that are built represent each sentence found in the cell of the selected row. Each sentence is presented for translation, where user enters data into a 2nd dynamically generated textbox.This all works great.Now I have a Listbox beside the 2nd textbox, which sometimes has 1 or more variables that need to placed into the translated sentence. I have set up a Hover menu over the listbox so that I can select the variable and insert it at the end of the sentence in the 2nd textbox. My problem is generating the click event on the dynamically created Listbox. Something like....
Protected Sub ListBox1_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged
TextBox1.Text = TextBox1.Text & ListBox1.SelectedValue
[code]....
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Jun 8, 2011
i just start programming in asp.net i struggling to add event handler dynamically. here is the scenario when the aspx page is load a link button is add with an event handlerpage load add link button and event handler with link button
Dim products As New LinkButton
products.Text = "Products"
testPanel.Controls.Add(products)
[code]...
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Sep 14, 2011
I have to create controls for inputting info to create people objects in the program, because I don't know how many people they are going to input, I have a button that they can press to add more fields.
I need to add a doubleclick event for these dynamic controls (text boxes), how can I create an event for them if they haven't been created yet. Also, as far as I know you cant make a variable part of an object name while declaring it. I need to do something like
Dim dynamicText & (Append variable counter each time a box is made)As New TextBox
dynamicText &variable counter. Name = "TimeTextBox"
dynamicText.Text = "SdgsdG"
dynamicText.Location = New System.Drawing.Point(100, 100)
[code].....
Also is there a way to like copy and paste a group of controls via code instead of having to code each individual one like if I had to do a text box along with a combo box and a lable all at once, can I throw it into something so I only have to recreate the container?
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Oct 16, 2011
I'm new to VB and trying to add a Key(Down? Press?) Handler to a dynamicly created textbox. The error I get is "'KeyDown' is not an event of 'Object'". How do I fix this?Here are the relevant parts of my
Public Class main
Structure square
Dim box As TextBox
Dim guessedVal As Integer
Dim correctVal As Integer
[Code]...
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Oct 2, 2011
Some controls are dynamically created within a panel. Their event handlers are attached
Dim btn as new system.windows.forms.button
with btn
'set properties
[Code]....
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Dec 13, 2011
I'm writing a small 2D engine that uses Lua to control it. I've been setting events up in between the Lua and the VB.net for the past little while here. The problem, I've realized, is that is that I can't seem to remove the events which is screwing up quite a few things (because they are being called when they should be done with). To fix this, I wanted to add some kind of way to remove the specific event handler.
I know how to add an event handler:AddHandler Button1.Click, AddressOf Button1Clicked
But with this in mind, is their a way to remove a specific event handler in the VB.net? I didn't explain this very well: If I have this:
[Code]...
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Apr 1, 2011
I have a Timers.Timer called COMTimeout, to which I add an event handler using:
AddHandler COMTimeout.Elapsed, AddressOf TimeoutEvent
however, the handler may also be:
AddHandler COMTimeout.Elapsed, AddressOf SecondTimeoutEvent
I now need to remove the handler, is there a way to do it without knowing the name or do I need to keep track of which handler as been assigned?
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Jun 20, 2012
VB.NET RemoveHandler & Anonymous Methods
If I add an event handler like this:
AddHandler s.Click, AddressOf Panel1_Click
How can I can then remove the event handler?
Private Sub Panel1_click(ByVal sender As Object, ByVal e As System.EventArgs)
' Remove code
End Sub
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Dec 16, 2009
I am having a problem with the cellvalidating event constantly firing when the datagrid is refreshed (since the trigger that fires the event is the originally selected cell losing focus).I would like to remove the event handler for this at certain points of my code so that it does not fire but the examples I have come across on MSDN don't appear to do anything, so I guess I must be doing something wrong.[code]
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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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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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Nov 2, 2010
I ma using DevExpress controls (which doesnt matter for this example). I have a lookupEdit control and I never want the EditValue_Changed event to fire. Can I use RemoveHandler to do this? If so can someone give me a code example of doing this? Should I put RemoveHandler in the load event of the user control I am creating? Or does it go in the EditValue_Changed event of the lookupControl?
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Mar 11, 2010
I want to after clicking on button2,after that if i click on button1 then msg is not displayed Public Class Form1 Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
[Code]...
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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 2, 2011
How to remove a handler set up by a lambda expression? According to this MSDN article, lambda expression should be assigned to variables which should be used to define handler operators. So far, I have used lambda expessions w/o variables.
For instance, the following works:
Private Sub ScaleObjectInit1(ByVal objSrc As NumericUpDown, ByVal objTgt As FrameworkElement) ...
AddHandler Me.upDnScale.ValueChanged, Sub (sender As Object, e As Object) ScaleObject1 (sender, e, objTgt)
End Sub
Private Sub ScaleObject1(ByVal sender As Object, ByVal e As Object, ByVal objTgt As FrameworkElement)
[Code] .....
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May 12, 2011
I have a Winform application where i added picturebox's to a flowlayout panel dynamically from code. I have successfully managed to add a handler for doubleclick and click events the problem i have is that when i add both together it only seems to work with the click event and not the double click. where I could bee going wrong? Iam using VS2008 .NET 3.5 my code looks a bit like this :
Public Class Class1
Dim WithEvents picturebox1 As PictureBox
Private Sub Brochure_Creator_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
[Code].....
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Jun 16, 2009
to know if a control have any handler. I have a dgv and in the editing control Showing event i add an event handler like this: VB AddHandler e.Control.KeyPress, AddressOf Grid_KeyPress_NumbersOnly This event it's added in some of the columns and for the other ones i remove it... The problem it's when the user, for example selects 3 columns where the event it's added, then if the user selects one where the event it's removed, it doesn't remove all handlers... So i have 2 solutions, when removing i put multiple removes or the other check if the event handler it's added doesn't add again. I prefer this second option, but i don't know how to check if the event it's added?
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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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