VS 2008 - Remove Handler - Use "WithEvents" And "Handles"
Aug 30, 2009
I am having some trouble understanding the different aspects of Event Handling. Of course, I know how to use "WithEvents" and "Handles". However, I have created some interdependent Custom Cotrols. I will try to describe this, and then post some code.
Assume a Custom Control 'GroupedListHeader", an instance of which is created by, and added to the controls collection of another Custom Control, "GroupedListNode".
GroupedListHeader adds an Event handler "OnHeaderClick" During initialization which hanndles several different events. As part of the handling in "OnHeaderClick", GroupedListHeader raises one of several Events which GroupedListNode in turn handles, again by using "AddHandler" during initialization. And so on. The events can propegate up through a chain of sub-components of my final control. I understand that I am supposed to use "RemoveHandler" somewhere, at some point, when I use "AddHandler". This is where my questions arise.
A. In the cases where I have used "AddHandler" to handle a custom event sourced by a sub-component, I get the following Waring:
Quote:
Warning2The '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.C:Documents and SettingsSuper God-like UserMy DocumentsVisual Studio 2008ProjectsGroupedListControlTestAttributesNode ComponentsGroupedListNodeBaseII.vb27446GroupedListControl
I am not quite sure what this is about, other than it seems to relate to trying to Remove a handler which is referencing another Custom Event.
An Example (The two in red are the source of the Warning): 'Added during the Constructor Method, after "InitializeComponent and some other Drawing-related Stuff:
AddHandler moTGHeader.Expanded, AddressOf Me.OnExpand
AddHandler moTGHeader.Collapsed, AddressOf Me.OnCollapse
AddHandler moTGHeader.Selected, AddressOf Me.OnSelect
[CODE]...
I should note futher that the component indicated above further propegates these handled Events upward to the parent of this component, where again, the same issue exists. What is it that makes the two items in red different from the others that they would cause this warning? How critical is it that I use "RemoveHandler" in this context? These events should persist until the control goes out of scope. Also, this is just an example; at several other levels in the hierarchy, I am doing the same thing. My understanding is this can result in objects retaining references to the Handlers(?) or something like that.
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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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Dec 5, 2011
I get the error on this line on [ListBox1]
[code] Private Sub ListBox1_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs) Handles ListBox1.SelectedIndexChanged
error
Quote:
Handles clause requires a WithEvents variable defined in the containing type or one of its base types.
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May 11, 2009
Just upgraded a VS 2005 ASP.NET 2.0 website to VS 2008 ASP.NET 3.5. There was an error on the Sub Button_Click. It seemed to be a minor error, the website and the button worked just fine, as usual. What does the error mean?
Protected Sub btnDEreports_Click(ByVal
sender As
[code]...
Error 20 Handles clause requires a WithEvents variable defined in the containing type or one of its base types.
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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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Feb 23, 2010
I've just opened a project I was working on yesterday perfectly well only to find it's gone nuts. I'm getting this error ..."Handles clause requires a WithEvents variable defined in the containing type or one of its base types."... on each one of my Sub declarations!
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Oct 6, 2011
I get the error
Handles clause requires a WithEvents variable defined in the containing type or one of its base types.
in the following code..
Public Sub selCurrentManuf_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) _
Handles selCurrentManuf.SelectedIndexChanged
End Sub
The drop list to go with it is the following...
<asp:DropDownList
OnSelectedIndexChanged="selCurrentManuf_SelectedIndexChanged"
selectedvalue='<%#Container.DataItem("c1_manufidcurrent")%>'
[code]....
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Aug 23, 2009
I created a lable to handle DateTime = Now, It works fine. but when I moved it inside a FormView I Get the following Message. Handles clause requires a WithEvents variable defined in the containing type or one of its base types?
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Mar 25, 2010
I am in the processing of moving an app from VB to C# but some of the classes I will just be moving to VB dlls to access from the main C# app. In doing this I am trying to get the VB dlls to utilize the main C# class lib. In this C# lib I have an abstract clase called base process, it sets up a background worker and handles all the progress tracking, errors, and even reports an ETA. To use this in a derived class in C# you would just do this...
public class SomeLongProcess : Common.Multithreading.BaseProcess
{
public void start()
[code]....
The problem is that if I do the equivelant in VB I get an error "Handles clause requires a WithEvents variable defined in the containing type of one of its base types". Well I can't do a WithEvents in the base class because it is C# so..
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Aug 26, 2011
I am trying to follow this thread
[URL]
and I have it pretty close but have one error.
Quote:Handles clause requires a WithEvents variable defined in the containing type or one of its base types.
That error is on both of these, in blue
Private Sub SpellChecker1_DeletedWord(ByVal sender As Object, ByVal e As NetSpell.SpellChecker.SpellingEventArgs) Handles SpellChecker1.DeletedWord
'save existing selecting
[code]....
I have added the reference, I have also added them to the toolbox. My dictionary is all set. What did I miss?
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Nov 22, 2011
i am getting errors on last two event handlers. what did i do wrong?
Error - Handles clause requires a WithEvents variable defined in the containing type or one of its base types.D:Shipping ApplicationShipping ApplicationForm1.vb75136Shipping Application
Error - 'PrintDocument1' is not declared. It may be inaccessible due to its protection level.D:Shipping ApplicationShipping ApplicationForm1.vb1119Shipping Application
[code]....
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Aug 9, 2011
My coding, I got error: Error Handles clause requires a WithEvents variable defined in the containing type or one of its base types.
For information i am using visual studio 2005. Here i highlight my probleam with in my coding
Public Class Admin
Private Sub TextBox6_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)
End Sub
[CODE]...
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Feb 2, 2010
When I attempt to run a program I just finished coding I get the following message: "Error 1 Handles clause requires a WithEvents variable defined in the containing type or one of its base types." Looked it up online and still does not make sense to me. If I need to paste code or anything else let me know and I will do so ASAP.
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May 16, 2012
when i am selecting form the xaml file a button and then tap event from the right (in order to set the tap event) it auto generates this sub :
[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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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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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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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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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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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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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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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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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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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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Jan 28, 2010
So I have a custom control that when added to a form will create two child controls inside it. The custom control's designer handles the creation of these. The problem I am having is that when the designer generates code for these controls only the parent control is declared "WithEvents". So my que
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Jun 24, 2009
I am trying to do the following:
Public WithEvents frmButtons(999) As Button
And then use it like this:
Private Sub frmButtons_Click(ByVal sender As Object, ByVal index As Long) Handles frmButtons.Click
Where the index variable has to represent the object in the array like this:
frmButtons(index).Text="..."
But it gives me an error:
'WithEvents' variables cannot be typed as arrays.
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Feb 22, 2009
I've got a TEXTBOX called CompanyName. And I've got a warning in the error tab that says:
WithEvents variable 'CompanyName' conflicts with property 'CompanyName' in the base class 'Control' and should be declared 'Shadows'.
Is CompanyName some kind of reserved keyword? I'm getting the same error for a textbox called Location. Can I ignore these warnings or must I rename my textboxes. My problem is the textboxes are named to match columns in a DB TABLE to allow me to do some auto-binding logic.
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Feb 15, 2012
(How to get The Handles Of process?)
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