I have a (legacy) form where I had to add the InvokeRequired/BeginInvoke(Delegate) to avoid the "Control control name accessed from a thread other than the thread it was created on." exception.This seems to work fine but there are some scenarios where the BeginInvoke is not calling the Delegate (which I can tell from the output log). [code]
View 1 Repliesinstead of using if control.invoke required in a procedure can I just call the procedure with begininvoke?I have, possibly, the following:
Private Sub UpDateTimer_Elapsed(sender As Object, e As System.Timers.ElapsedEventArgs) Handles UpDateTimer.Elapsed
UpdateTime()
If MicActive Then
PTTCancelTime += 1
[code]....
where is the best place to learn InvokeRequired and BeginInvoke.
View 4 RepliesI've created a Delegate that I intend to call Async.
[Code]...
Disclaimer: I know that Thread.Abort is evil. I'm using it as a last resort since some I/O functions (e.g., File.Exists when used on a non-existing network share) block for a large amout of time and do not allow you to specify a timeout.
Question: Is it possible to Abort (as in Thread.Abort) a worker thread started using Delegate.BeginInvoke or do I have to do the Thread handling myself?
I am trying to call a method that started on a background thread on the UI thread calling BeginInvoke and passing in a delegate as follows:
Dispatcher.BeginInvoke(Function() UpdateApplicationDataUI())
to call this method:
Private Sub UpdateApplicationDataUI()
...
End Sub
However, I get an error in the call to BeginInvoke (the UpdateApplicationDataUI portion of the delegate is stating "Expression does not produce a value").
Me.Dispatcher.BeginInvoke(Function() New Action(AddressOf UpdateApplicationDataUI))
Me.datagridview.InvokeRequired property means in vb.netadil
View 3 RepliesI have an annoying bug which is very difficult to replicate. When I start my application, from time to time, I get this error message "Invoke or BeginInvoke cannot be called on a control until the window handle has been created". This makes the user think the application is unstable... I have no idea what could cause this problem. The application uses a splash screen. It's built in Visual Basic using VS 2010 and .net framework 4.
View 1 RepliesI am referring to this document on MSDN. I understand what ".BeginInvoke" does, however looking at the example code on the document.[code]The delegate myDelegate (and the DelegateMethod) accepts a control and a string, but, at the .BeginInvoke, a Label control is passed and an array.[code]Shouldn't a string be passed instead of the array? Am I missing something?
View 2 Repliesi AM TRYING TO USE A THREAD TO UPDATE SOME CONTROL during runtime using invoke and i get this message.here is my scenario:im trying to build a performance monitor tooli have a mainform that is MDI parent and i create mdi child using
[Code]...
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.
so am i right to say that Multicast delegate is no different from a normal delegate other than the fact that it has arguments. so System.Action is a 'normal' delegate whereas System.Action(T)(Byval obj as T) is a multicast delegate?
I'm working with the DevExpress XtraGrid control.I have a routine that goes thru and adds all the controls on the current form dynamically, and launches on a seperate thread the routine for a given control to initialize it to the value that will be displayed to the end-user. Some of the controls are displaying calculated values, and take some time to return their values, so that's why we are doing it on a seperate thread.
[Code]...
I'm using a similar snippet of code for any control properties that have to be updated, and all work fine. On the above code when the actual Invoke is called, it APPEARS that the thread just ends and never calls the delegate, and doesn't return to finish either.
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)'.
So I have a custom control that basically acts like a listview, but it draws everything out and finds where the mouse is and all that.But when I have another class that goes in a chatroom and receives data, then raises an event to the parent (which is the main form), I then pass it through a delegate and then it adds to the custom control.This seems to take a lot longer to add items to the list than If I just use
Control.CheckForIllegalCrossThreadCalls = False and bypass the delegate?What should I do.
[code]...
Is there a faster way to pass all the info, or should I just bypass the cross thread check and not use a delegate?
I want to avoid paste operation in combox box control. to suppress the system context menu for copy and paste, I did following steps1) Create a empty new context menu (just drag drop new context menu on the form)
2) Assigned newly created empty ContextMenuStrip to combo box ContextMenuStrip property. Is it the right way to avoid right click system context menu? is there any other way to do so?
I have a filesystewatcher object. On it`s event it runs a procedure which fills a treeview with a data. I had problems with treeview methods, but when I run them using invoke method everything is ok. But I still have one problem. When I load the form for the first time, everything works fine. But, when I then close the form (me.dispose, me.close), and load it once again, when Filesystemwathcer start the procedure i have an exception "invoke or begininvoke cannot be called on a control until the window handle has been created" trying to run a treeview.invoke method?
View 9 RepliesI'm searching for a solution to resize image(jpg) being passed in from an array in Picturebox Control on .NETCF 2.0 in VB.NET without resorting to using the opennetcf library, is it possible?
View 1 RepliesThis code works fine in VB 2008 attempting to redo the program in vb2010:
in the GuiForm:
the following is declared in formgui:
Private Delegate Sub UpDateGSLDelegate(ByVal rpn As Integer)
Also the following sub is also in formgui:
Public Sub updateGSLDisplay(ByVal rpn As Integer)[code]....
"UpdateGSL", in turn, will be called from any subs running in another module in a separate thread.The purpose is to update one or more labels on formgui based on the "rpn" variable.now the program will just hang at " Invoke(New UpDateGSLDelegate(AddressOf UpDateTheGSL), rpn)" in the "updateGSLDisplay" sub. no error messages, just stops.also I'm now using the " Dim t1 As Task = Task.Factory.StartNew(Sub()" way to starting a new thread in case that is revelant.what has changed from 2008 to 2010 to cause this. Just started trying out vb 2010? How can I fix this in 2010?
I looked at this page: http:[url]...aspx but it doesn't say anything or maybe it does and I just didn't pickup on it.
I am using the under given code in a module and I am getting an error ['Me' is not valid within a Module]
[code]...
I had a question about some logic of the InvokeRequired with a ListView. I have the following
vb.net
Public Sub ListviewSub If ListView.InvokeRequired = True Then Dim t As New MethodInvoker(AddressOf ListViewSub) picCurrent.Invoke(t) Else RunSub() End IfEnd Sub
[Code]...
I read Accessing Controls from Worker Threads and implemented this
Private Sub myExplorer_Close() Handles myExplorer.Close
If Me.InvokeRequired Then
Me.Invoke(New MethodInvoker(AddressOf myExplorer_Close))
[code].....
I have the following test code. It does nothing useful, but it's there for me to understand VB:
Imports System
Imports System.IO
Imports System.Diagnostics
[code].....
I am working with tasks, so I've got the following code to update a label on my form:
Private Delegate Sub UpdateLabelDelegate(ByVal s As String)
Public Sub UpdateLabel(ByVal s As String)
If Me.InvokeRequired Then
Me.BeginInvoke(New UpdateLabelDelegate(AddressOf UpdateLabel), New Object() {s})
Return
I've got a set of controls in a line inside"FollowTableLayoutPanel1", contained within "TableLayoutPanel2".I have them resizing according to the position of the mouse cursor; the closer the mouse cursor is to the vertical centre of the control, the larger the control is. Because FollowTableLayoutPanel1 has its anchor property set to "Top", it recentres itself in TableLayoutPanel2.It is possible for the recentring of FollowTableLayoutPanel1 to move a control one pixel further away from the mouse pointer, which causes the control to shrink, which causes FollowTableLayoutPanel1 to recentre, placing the control closer to the mouse pointer, which causes the control to grow,which causes FollowTableLayoutPanel1 to recentre, which moves the control further away from the mouse cursor, etc., etc., etc.The end result is that the whole setup judders and wobbles, constantly resizing.Full example code is provided below,and can be pasted directly into Form1 of a new project. Positioning the mouse cursor to correctly show the problem is left as an exercise for the reader :
Public Class Form1
Private Sub myInitializeComponent()
Me.components = New System.ComponentModel.Container
Me.TableLayoutPanel2 = New System.Windows.Forms.TableLayoutPanel[code].....
This sub works fine:
Private Sub UpdateInfo(ByVal text As String, ByVal timeStamp As DateTime)
If Me.lstStatus.Dispatcher.Thread Is System.Threading.Thread.CurrentThread Then
' Do stuff with
[code].....
I am having a small 'head banging' experience working on one of our DLL products.The problem I am having is that this application is an outlook addin, and as such, does not own its own Message Pump. No problems there, I have a UI class, which starts a thread, and calls Application.Run(new fControlForm)
I use the Application.Run passing a form, rather than an ApplicationContext purely because I want this form to be in charge of displaying other forms: ie, I can use BeginInvoke to ensure that a second, and many more forms are created in the context of the thread that owns the Message Pump.
I however feel this to be quite hackish. I get a form displayed at startup (which I am sure I can hide if I needed to)My question: IS there any way to create some form of Invoke procedure in an applicationContext that uses the Message Pump thread? I have created a class which implements the ISynchronizeInvoke and can Invoke from a thread that it owns, however this is not the same as invoking from the Message Pump owner.
I am trying to write a VB.NET alternative to a C# anonymous function.I wish to call Threading.SynchronizationContext.Current.Send which expects a delegate of type Threading.SendOrPostCallback to be passed to it. The background is here, but because I wish to both pass in a string to MessageBox.Show and also capture the DialogResult I need to define another delegate within. I am struggling with the VB.NET syntax, both from the traditional delegate style, and lambda functions.My go at the traditional syntax is below, but I have gut feeling it should be much simpler than this:
Private Sub CollectMesssageBoxResultFromUserAsDelegate(ByVal messageToShow As String, ByRef wasCanceled As Boolean)
wasCanceled = False
[code].....
So from the comments section where this persons code was translated to VB.NET on [URL]it shows a little code to aid in calling cross thread UI stuff.
<System.Runtime.CompilerServices.Extension()> _
Public Function SafeInvoke(Of T As ISynchronizeInvoke, TResult)(ByRef isi As T, ByRef [call] As Func(Of T, TResult)) As TResult
[Code]....
Error 1 Data type(s) of the type parameter(s) in extension method 'Public Function SafeInvoke(Of TResult)(ByRef call As System.Func(Of frmLogin, TResult)) As TResult' defined in 'GvE.Globals' cannot be inferred from these arguments. Specifying the data type(s) explicitly might correct this error. C:GvEGvEfrmLogin.vb 37 9 GvE
I'm calling that code from inside a method defined in a form but that method is being called from another thread.
Just trying to avoid delegates and this is what the code above is supposed to do, but just can't get it to work.
I simply want to find documentation about invoke and begininvoke. A member of delegates. simply searching on it on bing and stuff don't show anything. It shows control.invoke, etc.In the delegate msdn entry there is no invoke member. At least not when I look for system.action or system.func.Where can I found begininvoke documentation? what will happen if I put nothing as callback function for example? Intuitively the program simply don't call any call back function but hei, I want to makes ure of it.
View 3 RepliesI have a thread that loads a control from the database during a long running operation. If I close my window before that thread finishes, it throws a Invoke or BeginInvoke cannot be called on a control until the window handle has been created., when doing the Invoke.I've modified the code to look like the following:[code]However it still hits the Invoke line and throws the error. When debugging stops on the exception, IsDisposed is true, .Created is false, and .IsHandleCreated is false.how do i prevent it from running the invoke line in this situation?
View 1 Replies