C# - How To Get Actual EventHandler Delegate Instance From An Event

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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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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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:

[Code]...

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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.

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Feraud

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The part for the delegate code is here

'---Event handler for the DataReceived event---
Private Sub DataReceived( _
ByVal sender As Object, _
ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) _

[code]....

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So I'm using a Open Source DLL file.The DLL-file got a "Public Custom Event" named: Hashed and I don't really know how to use it.The example is as follow: (C# Language)

c.Hashed += delegate (object o, TorrentCreatorEventArgs e) {
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Console.WriteLine("Overall {0}% hashed", e.OverallCompletion);
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from the documentation we have this: Multicast Delegate: Represents a multicast delegate; that is, a delegate that can have more than one element in its invocation list.

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Jun 19, 2012

I have a class that is in an assembly due to being required for other projects that I'm currently working on. One class lets call it Class Factory, creates a group of controls which require click event handlers to be attached, I have algorithms which determine polymorphic behavior based on certain features but that is relatively irrelevant.

Due to the event handler having to open up a specific form that isn't part of my assembly, and that form requiring this "Factory" class. Without creating circular reference is there any way I can essentially "delegate" the handler event for the form to define? As a simple work around I have had to maintain two separate classes, one in the project with the form and one in the assembly.

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Me.Width = 1500
Dim panel As New Panel
panel.Location = New Point(0, 0)
panel.Size = New Size(1000, 200)
[Code] .....

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Jan 28, 2012

I'm having problems with a program where I've got some multi threaded activities addressing the states of check boxes, which in turn are created by a user definable interface To achieve this I'm using the code below, which works on some occasions and crashes on other occasions when it stops with the following error NullReferenceException was unhandled Object reference not set to an instance of an object.Delegate Sub CBSetCallback(ByVal cb As CheckBox, ByVal value As Boolean)

Private Sub SetCheckBox(ByVal cb As CheckBox, ByVal state As Boolean)
If cb.InvokeRequired Then
Dim d As New CBSetCallback(AddressOf CBset)
Invoke(d, New Object() {cb, state})

[code].....

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I've created a Delegate that I intend to call Async.

[Code]...

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Code:
Public Class SendPings
Shared Sub New()
AddHandler Post.Saved, AddressOf Post_Saved[code].....

I get a error" Method 'Private Shared Sub Ping(item As BlogEngine.Core.IPublishable, itemUrl As System.Uri)' does not have a signature compatible with delegate 'Delegate Sub WaitCallback(state As Object)'.

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I need to transform the following in VB.NET from C# (.NET 4)

class XXX:

public event EventHandler ContentScaleChanged;
if (otherXXX.ContentScaleChanged != null)
{
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[Code]...

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[code].....

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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

[Code]...

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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.

[Code]....

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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Private Sub CompleteEventHandler(ByVal sender As Object, ByVal e As Microsoft.SqlServer.Management.Common.ServerMessageEventArgs)
SetControlPropertyValue(Label8, "text", e.ToString)

[Code]....

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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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Code:
Public Class Form1
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[code].....

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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

[code].....

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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;

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[Code]...

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Public Function GetBrowser() As WebBrowser
If TabControl1.SelectedTab IsNot Nothing Then
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[code]....

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Imports System.Windows.Threading
Class MainWindow
Private TimerList As List(Of DispatcherTimer)

[Code].....

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