Add Event Handler To Dynamic Dropdownlist
Jan 17, 2011
I have a page that contains dynamically generated Dropdown List controls and I want thant the dynamic dropdown list perform an AutoPostback to fill some other field using the value selected.[code]Control is correctly filled and rendered on ASP page but, after selecting a value, the page is reloaded (AutoPostBack is called) but the control is not diplayed and the sub is not called. I put a breakpoint into the ChangeValue sub but anything happens.I read on some post that handler for the first DropDownList is not necessary but, how is it possible to tell DropDownList to call my sub after changevalue?
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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 10, 2011
I've 100 buttons created dynamically in a form. how can i add event handler to them?
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Jul 29, 2011
I've created some dynamic controls on page load and added an event handler to handle the click event of a dynamic link button. Within the sub of the click event handler, I need to reference some other (non-dynamic) controls on the page and change their value. However, I get a null reference exception - object not set to an instance of an object - each time I try to reference a control on the page (in this case label1). What am I doing wrong in creating these dynamic controls or with my event handler?
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
'Get the data to populate the controls
[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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Aug 13, 2010
I would like to add handler to a dropdownlist which is dynamically created. I have the following code:
Dim ddl1 as new Dropdownlist
ddl1.DataTextField = "Hours"
ddl1.DataValueField = "HourID"
[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 7, 2011
Trying to select a dropdownlist item based on a value
Dim basedate As Date
basedate = "12/30/1899"
Label26.Text = basedate.AddDays(y)
ddate.SelectedIndex = ddate.Items.IndexOf(ddate.Items.FindByValue(Label26.Text))
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Jul 29, 2007
I have 2 dynamically created ddls in which the second ddl populates based on the first ddl and the values of both come from a database. These ddls are inserted into a table that is dynamically generated based on some event. My problem is that everytime I select a value in the first ddl, the page load event is called and I lose the table. Is there a way to NOT call the page load on a selection? Or is there a way to generate the table with the values of ddls as soon as the page loads. I tried to fix this problem
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Apr 21, 2011
I have two dropdownlists, the first is State & the second is City. I have the State ddl populated, but I would like to populate the City ddl via the selection in the State ddl. I am using autoPostBack, so it goes through the motion of updating but nothing loads. I am sure it is in the code behind or in the databind.
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Apr 26, 2011
I have 2 dropdownlists, one is State and the second is City. I am trying to create it so, when a user clicks the State, the second dropdownlist is populated with City names from a datatable.[code]
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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 26, 2011
I have a bit of a tricky scenario. It consists of some partial problems for which I have individually found solutions, but I couldn't find anything that makes it all work together smoothly.
-Upon selecting an item in a datagrid, a new page loads with the details regarding that entity.
-The entity represents a product that can have any amount of variants (such as a t-shirt's color or size)
-I dynamically add dropdownlists to this detail-page that represent these variants (there can be any amount of variants, and each variant can have any amount of different values, each value or combination or values from different variants representing a unique product entity)
-Upon selecting a different variant in a dropdown, a delegate is called that will change the session variable to the productId associated with the selected variant and a postback is fired that will reload the page with new data based on this productId
The problem: the postback is fired BEFORE the dropdownlist's (OnSelectedIndexChanged) delegate is called. Since this delegate defines the productId in the session, the new to-be-used productId isn't known at the time of postback.
Result: loading the correct data in the page is always delayed by one postback. Each time I change the selected index of any of the dropdowns, the page is loaded with data based on the session variable that the PREVIOUS OnSelectedIndexChanged delegate of the dropdown set.
I have a LoadData() method that sets the values of all textboxes, fields, labels etc. based on the productId stored in the current session. This method is called on Page_Load.
Private Property CurrentProduct As Product
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
LoadData()
[Code] .....
It seems that I haven't been completely clear on what does and doesn't apply to this scenario regarding Page Lifecycle.
1) My dropdownlists are added dynamically, which works fine on the first page_load.
2) The content of the dropdownlists is defined by what entity's details i'm loading on the page.
3) What entity's details I'm loading on the page is at first(not-postback) defined by the product I selected in a gridview in the previous page.
4) At postback, this entity is based on a sessionvariable containing the id of the entity.
5) This session variable is defined by what item in the dropdownlist I select.
6) This dropdownlist dissapears after postback since it's not defined on the page, but dynamically. So is the event.
So my guess would go towards some clientside script that stored the selected value before postback, but then I would be clueless on how to get that variable to the server since the logic that retrieves the entity is in the business logic layer which is far away from this page..
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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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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 15, 2011
I have a dropdownlist named ddlRoomName and a sql table name roomlist, when i run the sql command in sql it works fine.
But when i load the page the rooms do not load am i missing something obvious here?
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Page.IsPostBack Then
ddlRoomName.Items.Clear()
[Code]....
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Sep 7, 2010
Trying to get the findcontrol to work so I can set the default value of the dropdownlist I have in a template field, but I'm having no luck. Am I doing something wrong?
[Code]...
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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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