Event Addhandler, RemoveHandler Repetition Conundrum?
Apr 14, 2010
I'm getting a bit more fluent in VB.Net, but am still a bit green around the edges in certain aspects. I'm creating custom controls, and am starting to rely heavily on AddHandlers to manage them.Until recently, I didn't realize that you can add multiple event handlers for the same control and same address
[code]...
The above code would create 10,000 copies of the same event, and if I would click on combobutton1, the event would fire 10,000 times. I only need to fire the event once, but sometimes my code is a bit circular, and there may be an instance where two or more addhandlers are designated for a given control and address. Is there a way to have a loop on my custom dispose event where it would look something like:
[code]...
Or better yet, remove all events from a control(On a side note, is there any way in the debug mode to see all the active events attached to a control?)
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Feb 23, 2010
the concept of AddHandler/RemoveHandler with a very simple example?
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Sep 16, 2011
How do I use RemoveHandler with anonymous methods? This is how I add a handler for MyEvent event of the class MyClass
AddHandler MyClass.MyEvent, Sub()
...
End Sub
How do I then use RemoveHandler to remove the handler for the MyEvent event
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Feb 27, 2010
Using VB2008 Express I'm getting the following warning on a RemoveHandler statement and subsequent issues since the event is still hooked. Warning 1 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.
[Code]...
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Jan 25, 2010
I want to set an event handler only if this is not set:
If GetHandlers(MyWindow.Closed, AddressOf MyWindow_Closed).Length = 0 Then
AddHandler MyWindow.Closed, AddressOf MyWindow_Closed
EndIf
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Sep 28, 2009
I am comfortable with Vb.Net events and handlers.how to create event handlers in c#, and raise events.
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Nov 29, 2009
I am trying to build an add-on for some software. they are done using vb.net
I want to trigger an event called project selected but dont seem to get the option.
Ive selected the control but the event doesnt appear in the options list i can override the event by doing a Addhandler myControl.ProjectSelected, AddressOf newEvent is there any way in my newEvent method to run the orginal ProjectSelected event ??
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Oct 15, 2010
I have a form with about 40 checkboxes. Once a checkbox is checked, the div control's property should be changed from "none" to "block" or vice versa. I don't get an error, but the checkedchanged event isn't handled. Here is the markup:
<tr>
<td class="sectionSubHeader lightgrey">
<asp:CheckBox ID="chkbxCOMAEFund" AutoPostBack="true" runat="server" />[code]....
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Feb 1, 2009
I am currently writing a website for a company to display their products to their customers. One of the things I am putting into it is the ability to add news items onto the homepage, only part of the admin side of the site.
I have managed to extract some news items from the database, and display them dynamically in a Web User Control which I have added to Default.aspx. I have managed to add buttons for "Update" with events. The problem is that, on clicking one of these update buttons, the page reloads with the theme applied (as it should), but the css files from the theme do not apply - the body text is bigger than it should be and changes back to the default font. I know the skin files apply as I have tried setting all button backgrounds to black by default. The css files seem to apply to any text which is generated from clicking an update button (I have it so it writes the title of the news item for the button that was clicked. This text is the size and font it should be). I have spent HOURS trying to work out why this is happening, with loads of Googling but no success. It is almost as if the theme is being applied between the PageLoad event and the ButtonClick event, but the skin files would say otherwise. Does anyone know why this is?
[Code]...
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Aug 17, 2010
I'm instantiating an instance of FormQuoteCard from formQuoteList, formQuoteCard has an event and I'm adding an event handler to form1, but when i raise the event in form2, nothing happens:
[Code]...
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Oct 28, 2009
Perhaps surprisingly I haven't added an event handler programatically before and I'm having trouble getting my head around AddHandler.I am creating a series of DataGridView controls in a loop and want to subscribe to the CellFormatting event on each of them.The event handler signature is as follows;Private Sub ConfigureRows(ByVal sender As System.Object, yVal e As System.Windows.Forms.DataGridViewCellFormattingEventArgs)This works fine when I enter it in the visual editor properties box but I can't figure out how to give it the correct arguments using AddHandler.
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Jan 6, 2012
I am playing around with Drag and Drop, and I am having an issue with AddHandler. I am creating labels and displaying them on a form. Before I add each label to the form, I add 2 event handlers (DragEnter and DragLeave). When I run the code, it hits the first event handler (DragEnter), but doesn't hit the second event handler (DragLeave). Either I have coded something wrong, or the second handler is not being added.
Here is my code (note this is just something Im playing around with for learning):
Public Class Form1
Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
[Code]....
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Jan 8, 2011
I have a module that handles adding controls and populating values on a form. One of the controls is a button (there can be many) which acts as a lookup. For some reason, when I click the Button, it winds up in the btnLookup_Click event and displays the various messages, but it does not update the label (labLookup) text on the form. Am I missing something?
[Code]...
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Apr 12, 2011
So I have a bit of a problem and maybe I'm going about it in the wrong way UNPOSSIBLE! :-D
All I'm looking to do is create a few popup menus using contextmenustrips, it seems reasonable enough to me. What I want to happen is when I mouse over a label I want it to open up the contextmenu and THEN close once I am off the label and the contextmenu strip WITHOUT having to click the form. so I can go up and down a set of labels and popup menus as I move the mouse over each. This has turned out to be much harder than I anticipated. :-o
So at first I though ok lets try this code below. But this just causes the menu to flicker I "thought" focus would go to the contextmenustrip but i doesnt seem that way
Public Class Form1
Private Sub Label1_MouseHover(ByVal sender As Object, ByVal e As System.EventArgs) Handles label1.MouseHover
ContextMenuStrip1.Show(Label1, 20, 0)
End Sub
Private Sub Label1_MouseLeave(ByVal sender As Object, ByVal e As System.EventArgs) Handles Label1.MouseLeave
ContextMenuStrip1.Visible = False
End Sub
Private Sub Label2_MouseHover(ByVal sender As Object, ByVal e As System.EventArgs) Handles Label2.MouseHover
ContextMenuStrip2.Show(Label2, 20, 0)
End Sub
Private Sub Label2_MouseLeave(ByVal sender As Object, ByVal e As System.EventArgs) Handles Label2.MouseLeave
ContextMenuStrip2.Visible = False
End Sub
End Class
So then I thought ok well I'll just try to have it where when I leave the contextmenustrip I'll close that. THIS WORKS but not exactly how I want it to I can hit a label then jump onto the menu then off to another label but cant go label to label up and down the form.
Private Sub ContextMenuStrip1_MouseLeave(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ContextMenuStrip1.MouseLeave
ContextMenuStrip1.Close()
End Sub
Then I thought ok well how about something like
Private Sub Label1_MouseHover(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.MouseHover
If Label1.Focus Then
ContextMenuStrip1.Show(Label1, 20, 0)
Else
ContextMenuStrip1.Close()
End If
End Sub
But that didnt work either, I have another vb.net guy with me and hes all *shrug* I'm probably just going about this in the wrong way your suggestions are welcome. Thanks mucho everybody
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Jun 27, 2009
i have a form with text boxes for username, initials, and password on.Also on this form are a few checkboxes which at the minute i simply want to save their state to SQL as true or false depending if ticked or not. The checkboxes or text boxes are not bound to anything, and are used only for creating a new record in the table.There is a gridview below these boxes showing already created records.The code im using to insert to SQL with is:
If String.IsNullOrEmpty(UsernameTb.Text) Then
MsgBox("You must enter a Username!")
Else[code].....
For some reason when i create a new record, it saves the check state as -1 for checked, and 0 for unchecked. the table columns are varchar(5) for the check boxes.Using checkboxname.checkstate doesent work either - that saves the state as 1 or 0 (as opposed to -1 and 0)On another form i made for editing existing entries, i have the same text boxes and check boxes, which are bound so they show the record details. when using that form to EDIT an entry, it saves the check box states as "True" or "False" as it should do.Im completely stumped here, because if i create a new user it then breaks the gridview showing users, because it throws up error messages about "-1 not being valid boolean" when it attempts to render each check box in a grid view. how i can make the insert save the check box state as boolean?
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Jun 13, 2009
I hava a MDI app. i have a mdiChlid(say A) and others n instances of another mdichild. i wanto to this others n instances can handle an event generate in the A mdi chlid. How ca i do this??
[Code]...
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Sep 15, 2011
If I always need to call RemoveHandler after using AddHandler, where is the best place to do so? I have searched several similar questions as follows, but I do not quite understand.When and where to call the RemoveHandler in VB.NET? AddHandler/RemoveHandler Not Disposing Correctly..I thought garbage collection in c# or vb.net will take care of unused objects. Also, in vb.net designer, it automatically generates Dispose Sub. So I did not pay attention to programally releasing resource at all. Will I have any memory leak problems? Please kindly provide me some links/documents for me to start learning.[code]
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Apr 27, 2010
I am working to a VB.NET windows forms projet in .NET 1.1. And I have this type of architecture, very simplified.[code]...
Depending of the type of test I am doing I create an instance of a specific test derived from BaseTestLogic. But I found that after hundreds of object creations I can have StackOverflow exception.
I checked my code and saw that I forgot to remove the handler to Timer Tick. The question is, where and when is it correct to remove hadler?
Do I need to implement the IDisposable interface in the base class and RemoveHandler in Dispose?
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Feb 5, 2008
The VB documentation shows the Syntax for RemoveHandler statement as:
RemoveHandler event, AddressOf eventhandler and shows a Sample usage as:
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Jul 1, 2011
To streamline code, I increasingly rely on lambda expressions. But I may have hit against the wall in the attempt of removing an event handler set by a lambda expression. This really eludes me. The code below shows two samples: Alt1 uses a plain lambda expression as delegate and works fine: the object size increases as the numeric control varies. However, the drawback is that the handler cannot be removed:
RemoveHandler Me.upDnScale.ValueChanged, Sub(sender As Object, e As Object) ScaleObject1(sender, e, objTgt)
According to this MSDN article, a variable should be used to set/remove lambda based handlers. Alt2 shows a couple of attempts, but none works.
[Code]...
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Feb 18, 2010
I have attempted to understand the behind-the-scenes stuff for Events several times. I must have read at least a dozen articles but there is still some ambiguity in my head.
[Code]...
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Jan 2, 2012
I have this code:
Dim combinations As New List(Of String)
Dim word As String = "abc"
For c1 = 0 To word.Length - 1
[code].....
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May 26, 2011
How can I write all possible combinations to the console? For example, if user enters abc, then it will write aaa, aab, aac, abb, abc, acc, bbb, bbc, ccc.
Here's some code:
Dim abc() As String = {"a", "b", "c"} '
Sub Main()
Console.WriteLine("Enter the amount of characters")
[Code]....
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Jun 2, 2011
the code for adding items in the combo box but without duplicates. i have an assignment which is a simple web browser. the combo box will be the address bar. and everytime i input an address, it will be added in combo box and should not repeat just like in the browsers
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Jun 2, 2011
I have written an if...else statement which uses an array myArr and a string myStr as follows:
If myArr.Length > 0 AndAlso myArr(0) = "-1" Then
'Do stuff 1
ElseIf myStr= "xyz" Then
'Do stuff 2
ElseIf myArr.Length > 0 Then
[Code]...
It works exactly as I need. But It looks really confusing, mostly because the array length is checked twice. There must be a clearer way to write it, but I can't think of one. the order that each statement is executed is crucial. i.e. Stuff 1 has priority over stuff 2, which has priority over stuff 3.
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Nov 20, 2009
Say you press and hold down a letter on your keyboard. The first letter gets added, there is a delay and then it repeats quickly on screen. Is it possible to skip this delay and go straight to the repeating part? I realize this might not be a visual basic question as much as a windows question, but if there is some way of toggleing it through my program, or using a workaround, i would like to hear the alternatives ^^ Setting the windows setting to fastest still has a small delay and others users would still experience it on other computers.
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May 2, 2008
I have a button that when you click executes a certain code, lets say I make a menu that when clicked on should execute the same code, so how can I do this without having to copy/paste the same code twice.
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Apr 1, 2008
Got a form linked to a database and i have the first column of data appearing in a list box on my form. In the database there are two records with the same value and so, of course, in my list box the value is given twice.How do i remove this repetition from the list box? (still keeping it the same in the database)
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May 3, 2011
Here is the problem: In this question, you create an application that displays a multiplication table similar to the following figure, where x is a number entered by the user and y is the result of multiplying x by the numbers 1 through 9. Multiplication Table
[Code]....
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May 11, 2012
I need to stop the execution of a program in VB.net. Within a repeating structure the program checks whether a variable is true or false. When the variable is false I need to stop the program execution. I do not want to close the program but simply stop it. One way I found was raising an exception, but I would not want to display the error message to the user. What is the best way to do it ?
Do
If myvariable=false then
throw new exception... 'Silent exception
end if
Loop until ....
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