Events - EventHandler Managment In .NET?
Aug 19, 2009
I am right now in an project using VB.NET and needs to translate this C# code into VB.NET
oldCommand.CanExecuteChanged -= commandReference.CanExecuteChanged;
newCommand.CanExecuteChanged += commandReference.CanExecuteChanged;
For me it seems like the an event hooking up on an another event?But I have tried everything to translate this into VB.NET code?I have found out that EventHandler management in VB.NET is far from as good it is in C# as many other things.
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Nov 24, 2009
Ran into this while converting a VB.NET interface to C#; the VB version defines an event which doesn't conform to the typical (object sender, EventArgs e) signature:
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Apr 20, 2012
i have problem in vs2011 betai have database file and i attach it to vs2011 but when i open the connection this error appeared
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Nov 18, 2009
I have created a button its function to get the date and write it in a text box , and the month in anther text box while the year will be in four text box each digit will be in 1 text box
for example:-
{
(25/12/2009) }
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Jul 22, 2009
I went ahead and made a fresh database and a fresh VB app to make this as easy as possible. I'm running what i believe to be the most up to date software, both 2008 express editions. I want to add a data source in VB to connect to my database in the Sql management studio. I click add connection data source = Micro. SQL Server compact 3.5 I navigate to the DB file Then I get an error "you do not have permission to open this file."
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Nov 26, 2009
I am creating a password managment tool and for the storage I will be using a text file, I want to encrypt so I decided I will use the Rijndael cypher. I have found source code which does this to a file:
http:www.codeproje...ncryptFile.aspx. It is well explained but I am but still struggling to understand parts as I never looked at cryptography at all before.
Private Function CreateKey(ByVal strPassword As String) As Byte()
'Convert strPassword to an array and store in chrData.
Dim chrData() As Char = strPassword.ToCharArray
'Use intLength to get strPassword size.
[Code]...
This assigns all of bytekey with half of the hash from byteresult. Am I correct? If not why not just use SHA256 instead of SHA512 as you are only using half of the hash. If somebody could explain this to me this would be great. Already confused and this is just creating the key, then the IV needs to be created(not sure what an Initialization vector does) then the encrypt/decrypt function. I think I will struggle understanding this but I am going to try.
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Jun 15, 2011
I'm dynamically adding an event handler on a link button, first when the page is load o create a link button with product category. On clicking the product category it fires an event and passes the product-id IN sender object.
Here is my problem: when i readd the event handler on page load it's giving an error cannot cast sender object
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Dec 7, 2011
I'm having trouble wrapping my head around Events and their Handlers in general. I was working from some sample code that used them, and I can't understand why use an event rather than simply using a sub. I'm absolutely sure I'm missing the bigger picture here.
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The Event allows a class to say 'Do something when this happens' in a very ambiguous way, leaving the class which created the Object to define a Handler; what that action should be. That Handler can, and very likely will, be unique to each instance of the class.
It seems to me that this would likely be achievable (on a basic level) through indexing and enumeration, but that would get messy and become a lot of code to write rather quickly. This is probably a much more flexible and extensible way of handling things. I'm going to post this anyway, in the hopes that I'll get someone to tell me whether I am correct in my observations or totally off base, and that it helps someone else who is having trouble with this concept as they dip their toes into OOP and event driven objects.
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Jun 7, 2010
I'm using the below to update controls from another thread (works great) How would I call a Sub (Named UpdateList)? The UpdateList updates a listview with a list of databases on a selected SQL instance, requires no arguments.
Private Sub CompleteEventHandler(ByVal sender As Object, ByVal e As Microsoft.SqlServer.Management.Common.ServerMessageEventArgs)
SetControlPropertyValue(Label8, "text", e.ToString)
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Mar 4, 2009
I have found a sample code of something I am trying to complete in VB.Net however the sample is in C++, and I am having a hard time understanding how to translate it.
I have everything basically covered except for the actual EventHandler line.
[Code]....
I would like to know how to translate this easily into VB.Net. I understand i may have to create an Event and a Raise Event, but not sure how.
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Aug 7, 2009
Back in form1, how can I wire up the Click event for each MenuItem present in the contextmenu? I want to do this as abstract as possible, meaning I don't want to implement the OnClick code inside Form1.
Code:
Public Class Form1
Me.ContextMenu = MenuFactory.BuildMeAContextMenu()
End Class
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Jul 1, 2009
Me.SetProgressBars()
AddHandler zip.SaveProgress, New EventHandler(Of SaveProgressEventArgs)(AddressOf Me.zip_SaveProgress)
zip.Save(target)
Took some snippets from a MSDN page and molded it into my project ... problem is on every run its setting a value of -1 to something and i cant for the life of me figure out what to!
Private Sub zip_SaveProgress(ByVal sender As Object, ByVal e As SaveProgressEventArgs)
Select Case e.EventType
Case ZipProgressEventType.Saving_AfterWriteEntry
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Mar 15, 2011
I have 2 classes that Implement 1 EventHandler. Its part of a fingerprint scanner API but I'm having some issue and I'm not sure if it is my fault in how i use the Implements.Is it ok to have 2 different classes Implement the same EventHandler? Each class then uses the events differently within the class but it almost seems like there is some overlap that is causing some issues. I know this is hard to explain without posting code but since i can pinpoint the problem, idk what to post. My main point is, can you have 2 different classes Implement the same Interface?
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Apr 22, 2011
I wish to check the hard drive space used in a folder on a hard drive. This will happen continuously as a service, so it will be calculating the space used for thousands of folders all the time. I know that this code can be done easily in dotnet, but it seems to take a really long time. Are there any APIs to do this more efficiently, or does the entire looping process have to occur to do this check?
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Jan 8, 2010
How can i cancel the eventhandler, i have a problem with tab browser is that:- i have a set of button image to show the forward and back button which are disable or enable (like IE).Inside my program which are deal with the web_CanGoForwardChanged and web_CanGoBackChanged event.my problem is that if i click on other tab faster than the eventhandler done,i got the wrong image shown on button.how can i stop the eventhandler to prevent the wrong image.
Public Function GetBrowser() As WebBrowser
If TabControl1.SelectedTab IsNot Nothing Then
For Each c As Control In TabControl1.SelectedTab.Controls
If TypeOf (c) Is WebBrowser Then
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Jan 5, 2012
I'm working on a project that will require me to react to 5 separate events generated by an external device and then do something after a certain delay. The events will normally happen one at a time but may occasionally be simultaneous.
Imports System.Windows.Threading
Class MainWindow
Private TimerList As List(Of DispatcherTimer)
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Apr 24, 2012
I am trying to clone some of my Controls, with their EventHandlers. I have a function to retrieve the Delegate of a specific EventHandler.The hard part is to find the correct naming to use.
This is the function I'm using
Private Function GetEventDelegate(ByVal ctrl As Control, ByVal eventname As String) As [Delegate]
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Aug 4, 2011
I am trying to clone some of my Controls, with their EventHandlers. I have a function to retrieve the Delegate of a specific EventHandler.The hard part is to find the correct naming to use.
This is the function I'm using
Private Function GetEventDelegate(ByVal ctrl As Control, ByVal eventname As String) As [Delegate]
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Oct 29, 2011
I'm working on a project that will require me to react to 5 separate events generated by an external device and then do something after a certain delay. The events will normally happen one at a time but may occasionally be simultaneous. Is this a bad idea and if so why?
Imports System.Windows.Threading
Class MainWindow
Private TimerList As List(Of DispatcherTimer)
[code]......
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Feb 19, 2008
I'm having a really weird problem with my current project in Visual Basic 2005.To make a long story short, I have an EventHandler subroutine (Clock1_tick) which triggers on the Elapsed event of a Timer (Clock1). Some, but not all, of the code within the subroutine executes correctly. Some of it doesn't execute at all, even though the debugger shows that each line of code is being read.
The overall details of the program aren't really important, but within the program I have a VB class file which can be instanced via the "New" keyword and contains a series of functions, subroutines, and properties... a typical class file. The class file is for managing sound channels..The frmMain includes a status bar with a label to display the program's current status. It also includes a public sub which recieves a string and sets the text of the status bar:
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Apr 26, 2012
I have an Unhandled Exception handler that does something like this[code]...
So it looks like from the "add" that the last person that subscribes to Application.ThreadException is the one who gets it (it's not additive as most event handlers are). I don't want to give up my subscription to this eventhandler no matter what. Can anyone think of a way that I could track when I lose my subscription to the Application.ThreadException so I can steal it back from whoever stole it from me?
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Jan 23, 2009
I'm creating multiple ComboBox and multiple TextBox at runtime and would like for the TextBox BackColor to change when an item in the associated ComboBox is selected. I was able to do this before with a single TextBox and single ComboBox I added during design, but I really don't understand how to tackle this.
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Nov 5, 2010
In C#, I could do something like this:
EventHandler handler = this.SomeEvent;
...which would allow me to, for example, do:
Delegate[] attachedHandlers = handler.GetInvocationList();
In VB.NET, I can't seem to figure out how to do a similar thing.
This doesn't work:
Dim handler As EventHandler = Me.SomeEvent
...due to the following error:
Public Event SomeEvent(sender As
Object, e As EventArgs)' is an event,
and cannot be called directly. Use a
'RaiseEvent' statement to raise an
event.
But this doesn't work either: [Code] So how can I actually get an EventHandler from an event in VB.NET? The only idea that's immediately coming to mind is to use reflection, but that seems pretty ridiculous.
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Dec 9, 2011
I am using Visual Studio express 2008 to load a form, perform a task at a given interval. My problem is:
1) I am able to populate a textbox with the desired text (a pathname);
2) I can get the timer event to work perfectly;
3) The problem arises when the timer conditions are met and I need to perform a task based on the value of the text box.
4) The value from the textbox becomes lost and when i hold my mouse cursor over the textbox:
[Code]....
On a side note, the script runs perfectly when i hard code in the pathname, but this doesnt suit the work i would like this script to do.
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Jan 13, 2010
I have a Dialog Box that creates a Link Label for each item in a list.When one of those LinkLabels is clicked the DialogBox raises a LinkClicked event.Before, I was using code like this in the Form that was instantiating the Dialog:[code]But I don't like that for several reasons.What I want to do, and what I thought would be straight forward, was to pass the AddressOf the UserClicked PoLink Method into the ShowClickableLinksDialog Constructor and do an AddHandler within the constructor and also assign the Delegate to a Property on the Dialog so as to RemoveHandler when the Dialog is Disposed.[code]But I get a squiggly on the tempLinkClickedEventHandler after the AddressOf Operator saying: "AddressOf operand must be the name of a method (without parenthesis)"I don't get it.I've played around with a number of permutations and can't get what I feel ought to work, to work.
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Dec 29, 2009
I do have a customized treeview which inherits from treeview. The customized treeview offers - amongst other - the functionality to automatically check/uncheck the child and parent nodes according to the selected node.To do so, I use (or mabye abuse?) the AfterCheck-event of the treeview in the class where the inherited treeview is customized. Code looks like that (Submethods not included):
[code]...
I temporarily remove the AfterCheck-Event in the event-procedure to avoid it getting fired when I programmatically check/uncheck the checkboxes of the treeview. Works fine so far, only problem I see: if another programmer wants to use the customized tree view and tries to make use of the After-Check-Event, he'll get caught in an infinit loop, because his own After-Check-Event (he added himself to the treeview) was not removed and keeps on firing every time a checkbox is automatically checked/unchecked.
How can I remove ALL methods linked to AfterCheck-Event without knowing which method someone added to the treeview-control? My guess is to use reflection and to get the underlying delegate of the AfterCheck-Event by using the .GetInvocationList somehow - but I was not able to make it work.
Feraud
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Oct 13, 2011
I have been trying to implement the jQuery weekcalendar using .net. What I can't seem to figure out is why weekcalendar states events.events is undefined after I make an ajax call to a webmethod I created which returns JSON. Below is the relevant code:
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Aug 2, 2009
I want to make Keybord events and mouse events for learning and educational Purpose.
1. In Form any object like A "picture box" move by Arrow keys .
2. Picture Box Contain many Picture i want change Picture With next and Previos By Arrow keys.
3. I contain Voice of alphabet in Mp3.When i Press any button in textbox then its work.
4. Mouse Pointer Change My Own.
5. I click any Object or any thing By mouse its noice clicking sound like Tik Tik Tik.... Question No 3 is very hard to do . but not im possible
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Dec 31, 2010
I created a control that has picture box control docked within it. This control allows me to "animate" the image by swapping them out by setting the interval to swap them at. I want to use this control kind of like an animated icon within a application, but because the picture box is docked, the control I created won't respond to the events, MouseHover specifically. [Code]
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Sep 15, 2011
We are developing an application that looks like this: Mainwindow - PaneGroup - Pane
What we want to do is add a handler (AddHandler Pane, AddressOf MethodName) on the mainwindow and throw the event in the Pane. When we want something to change on a collection in the mainwindow, we throw that event in the Pane.
My question is if the pane is removed from the panegroup (doesn't exist anymore), does that handler still live on the mainwindow?
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