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
the concept of AddHandler/RemoveHandler with a very simple example?
View 28 RepliesI'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
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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:
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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?)
Not sure what to call this, but I have a number of dataseries that are being updated through an API connection. My form has charts that shall display the data, and I want the charts to subscribe to the update events raised by each data series. So I need the form class (or one of its member objects) to send a request to the BLL. But I don't want it to dig into the tree structure of my BLL by get to the desired data series. So.. I guess I must either send my chart object as just a "type Object" down to the BLL, to add the handler.. Or, I must request an anonymous object of the dataseries event to be sent to the form class? Am I on to something here? What to prefer? And how do I actually do this stuff?
Also it's a question what to add the handler to? I try to refactor my code as much as possible, so I try to make type of "Manager objects", like for example instead of adding chart object directly in my form class, I make a ChartManager class that the main form has a single object instance of. Then this manager has a list of chart objects etc.. This is like a UI logic layer, and will take a reference to the mainBLL object instance from the Main form class. I guess it's proper to add the handler directly to the low level ZgChart object...
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I try to replace the classic For Each with the LINQ ForEach method in VB.NET
Dim singles As New List(Of Single)(someSingleList)
Dim integers As New List(Of Integer)
For Each singleValue In singles
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How should I correctly do it (using anonymous methods = without declare a new function)?
I am trying to get my code working as per the instruction on [URL]So far I have the wrapper:
Public Delegate Function PredicateWrapperDelegate(Of T, A)(ByVal item As T, ByVal argument As A) As Boolean
Public Class PredicateWrapper(Of T, A)
Private _argument As A
Private _wrapperDelegate As PredicateWrapperDelegate(Of T, A)
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Then I try to call it from my code:
Dim children As List(Of String) = toplevel.FindAll(New PredicateWrapper(Of Integer, Integer)(Did, AddressOf DidMatch))
I then get an error on DidMatch ... Error Method 'Public Function DidMatch(item As DeptMenuData, did As Integer) As Boolean' does not have a signature compatible with delegate 'Delegate Function PredicateWrapperDelegate(Of Integer, Integer)(item As Integer, argument As Integer) As Boolean'.
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]
View 1 RepliesI 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?
The VB documentation shows the Syntax for RemoveHandler statement as:
RemoveHandler event, AddressOf eventhandler and shows a Sample usage as:
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.
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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.
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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.
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I'm a Linq noobie, maybe someone can point me in the right direction. What's wrong here? These anonymous types seem to have the same signatures.
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This is the original code in c#
public class CategoryRepository: RepositoryBase<Category>, ICategoryRepository
{
public CategoryRepository(IDatabaseFactory databaseFactory)
: base(databaseFactory)
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Does anyone has an idea what i should change to let it work and let my UserRepository use the methods in RepositoryBase while implementing the IUserRepository?
I am working with a vb program, but there is something strange on one of my .vb code pagewhen i put the "dot" afther the object name its dont show the methods availables for this objectbut on other vb code pages i can see it. but in this one no.for exmaplethis is a piece of code: Dim sb As New StringBuilder()
View 3 RepliesI am not sure how clear my question is by the title, but I am trying to make Class methods instead of Instance methods in Visual Basic that way I don't have to waste memory and code creating temporary objects to execute methods that don't need instance variables.
I am not sure if you can do that in VB but I know you can in Objective-C by using either a "+" or "-" sign in front of the method declaration. And in C++ (at least I think, I can't remember) you put the static keyword or const keyword in front of the function.How would I do this in VB if it is possible? Or should I just make a separate set of functions that are not members of a class?
Public Class Form1 Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Dim someproc As Process
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I am sure i am doing something terribly wrong, but i should better ask the experts.
At the third line i get the error Value of type <anonymous type> cannot be converted to <anonymous type>
Dim Query = (From c In Db.web Select New With {.AA = c.AA}).ToList
Dim v = New With {.Amount = 108}
Query.Add(v)
I can't figure out why my addhandler is not firing?In the Sub "CreateTagStyle" the AddHandler is not firing when the LinkButton is clicked Is there some reason that addhandlers can't be added at certain points of the page lifecycle?
<%@ Page Title="" Language="VB" MasterPageFile="~/_Common/Admin.master" %>
<script runat="server">
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
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My add handler is not correct for some reason. I don't know what I have incorrect. trying to add a row to the datatable upon formload. it says that NewM8_CustomersRow is not an event for BA_TruckingDataSet.M8_CustomersDatatable
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I came across a snippet of C# code which is very useful. I am trying to convert it to VB.NET, but can't seem to.
timer.Tick += delegate { panel.Children.Add(source); timer.Stop(); };
Is it possible to translate this to something similar in VB?
problem with AddHandler with parameters.
i've create a control, here is the code:
Public Class myWorker
Public Event Complete()
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When using a ReadWriteLockSlim for multi-threading support, do I need to EnterWriteLock when using AddHandler? [code]
View 1 RepliesI am creating a dropdown list in code for a gridview. I want to create an addhandler so I can have access to the selectedvalue. However, here (Rowdatabound) the add handler does not get fired off. How should I go about this?
Protected Sub GridView1_RowDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewRowEventArgs) Handles GridView1.RowDataBound
''//------------does not fire off add handler-----
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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
I have a number of UserControls that have the same event .
When I use an Object instead of UserControl, I can not use Addhandler.
Here is the simplest example of my problem: In this example error is "TextChanged is not an event of Object"
Dim obj As Object = TextBox1 AddHandler obj.TextChanged, AddressOf text_changed_event I have to use this structure, because in a FOR loop I use some different UserControls as obj. All UserControls have the same event.
Is there a way to use this structure without error?
Maybe there is a way to define a new object that covers all my UserControls.
I have a number of UserControls that have the same event .When I use an Object instead of UserControl, I can not use Addhandler.Here is the simplest example of my problem:In this example error is "TextChanged is not an event of Object"
Dim obj As Object = TextBox1
AddHandler obj.TextChanged, AddressOf text_changed_event
I have to use this structure, because in a FOR loop I use some different UserControls as
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The addhandler function works this way: AddHandler Button1.Clicked, AddressOf Button1_Clicked, However, I have an unknown object: Dim o as Object, But I can't add handler for this object AddHandler o.SomeEvent, AddressOf SomeFunction, How do I add handler for unknown objects as stated above?
View 2 Repliesbeen banging my head against this problem for days now. Hopefully somebody could point me in the right direction =) I have some button functionality in my Master Page:
Sub Run()
Dim Hbtn As Button = New Button
Hbtn.ID = "hLink"
Hbtn.Text = String.Format("H")
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I am creating a dropdown list in code for a gridview. I want to create an addhandler so I can have access to the selectedvalue. However, here (Rowdatabound) the add handler does not get fired off. How should I go about this?
Protected Sub GridView1_RowDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewRowEventArgs) Handles GridView1.RowDataBound
''//------------does not fire off add handler-----
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