.net - Control.Invoke Never Calls Delegate?
Oct 1, 2009
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.
View 2 Replies
ADVERTISEMENT
Feb 9, 2010
I've created a Delegate that I intend to call Async.
[Code]...
View 2 Replies
Mar 5, 2009
I'm trying to figure out if it is possible to instantiate and invoke a delegate by name, rather than explicitly. I think the code below explains it fairly well. I want to accept a function name and then instantiate the delegate based on that. In the example I use a select case, but I want to eliminate that and just use the methodName argument itself.
Private Delegate Sub myDelegate()
Private Sub myDelegate_Implementation1()
'Some code
End Sub
Private Sub myDelegate_Implementation2()
[Code] .....
View 4 Replies
Sep 1, 2011
I understand that .NET is multi-threaded and that is a good thing, but I continually run into issues when I have a background worker for example that is updating some control on my form and I have to do:[code] My question is why is this not built into the framework - surely if I am trying to update a DataGridView it should be intelligent enough to know when the update is from another thread and it could do all the above itself?
View 3 Replies
Jul 9, 2009
after finally fixing many problems with my program, and finally fixing it so it could run in a backgroundworker... I started to learn INVOKE but a small problem with this. Im not sure.. do I have to INVOKE for EVERY component of a FORM I want to modify? or is there a way to group all the invokes into a single big one?or a groupbox could work?
If progreso1.InvokeRequired Then
progreso1.Invoke(New updateprogressbardelegate(AddressOf updateprogressbar), New Object() {Me.ProgressBar1, valorprogreso})
[code]....
View 4 Replies
Aug 16, 2010
I have some code in c#
BeginInvoke(new MethodInvoker( delegate() {myAppMethod_Tick(sender, e); }));
Now, When I tried to convert that code to vb.net I have below..
BeginInvoke(New MethodInvoker(Function() Do myAppMethod_Tick(sender, e) End Function))
But it does not compile.. What's problem for it?
Because my c# application works ok without any problem..
View 3 Replies
Feb 3, 2009
I have a few textbox for data display and RS232 communication in my application. After I send characters on RS232, I want text boxes display feedback characters from RS232 receive. So in SerialPort_DataReceived() i was told to use Invoke to display received characters on TextBox1, TexBox2.how to define delegate for TextBox1 and call Invoke()?
View 9 Replies
Oct 12, 2010
I'm hacking away at some code which seems to have been started, at least in theory, as an MVVM project in Expression Blend, by my predecessor at this company.
I've got a thread running in the background, which is running some operations on items as they happen. In order to prevent any clashes, I've also got that thread running any operations my users call for.
Once those operations are completed, I'd like to bring up a MessageBox to give a summary of the user-initiated operations, but now that they're running off in their own thread, the finishedProcessing event handler is now running on the background thread instead of the interface thread and it's causing my MessageBoxes to appear non-modally.
Back in the WinForms days, I'd have handled that using InvokeRequired, Invoke and a Delegate. I've read that this has been replaced by something called "Dispatcher", but the ViewModel class I'm using doesn't seem to have a Dispatcher object.
The "thisViewModel" class I'm using inherits a class called "WorkspaceViewModel", which inherits "ViewModelBase", both of which look generated to me...
where I can link up to this "Dispatcher" from here?
View 1 Replies
Oct 4, 2010
What is the Invoke syntax to marshall data from a background thread receive callback method to a function on the UI Thread?(Form1).
Public Class Form1
MyDelegate = New DisplayData(AddressOf DisplayData)
Private Sub Form1_Load()
MyDelegate = New DisplayData(AddressOf DisplayData)
[code]....
View 12 Replies
Aug 27, 2010
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 Replies
Oct 25, 2009
I'm running into a strange error and I can't move forward Consider the following code
View 1 Replies
Aug 4, 2010
D is a dictionary whose entry values are of Type T..What I'm attempting to do is have a delegate like "Serializer" below that I can invoke on an instance of T, such as "Entry.Value" below.Please see the "return Entry..." line below for my wishful thinking.[code]
View 2 Replies
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].....
View 1 Replies
Mar 16, 2010
I've got the following code:
[code]...
The problem is that, when I call the "SetStatusBarText" sub from another thread, InvokeRequired is True (as it should be), but then my threads stall on the Me.Invoke statement - pausing execution shows them all just sitting there, not actually invoking anything.
View 1 Replies
Jan 30, 2010
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?
View 5 Replies
May 8, 2010
What the Win32 API is? I have looked around but no where really outlines what it is. Is it basically a set of procedures, outlined by Microsoft for programmers in order to get services from the operating system? In essence is it the equivalent to making system calls abd and library calls in UNIX? And yes I now Windows makes library calls too.
View 2 Replies
May 31, 2009
I'm just starting to look at Custom Controls after watching a MS video online. Video Training - WindowsClient.net I wondered if it's possible to get the name of the control that calls the OnEnter event that I am running.
[Code]...
I wanted to add a new combobox to the form and it always call this GetComboList each time OnEnter BUT I need to pass the combobox that the onEnter is firing from. Would save code and give me an insight into how custom controls work.
View 1 Replies
Aug 20, 2009
1. On the main form a scanner class is instantiated that (in the scanner's constructor) sets the scanner settings (baud rate, parity, etc) and opens the scanner for use
2. A barcode is scanned (via a scanner connected to the device in a seral port) while on the main form
3. In the scanner class, the DataRecieved event gets the needed info from the scanned code.
4. Then that info is passed back to the main form to a method RunCommandCode (which takes the scanned info as an argument)
5. On the main form the RunCommandCode calls another method CommandCodeHandler, passing the scanned info again
6. In the CommandCodeHandler sub a method is called in a Utils class (SetSelectedTab), which interacts with the form itself (determines how many tabs exist on a tab control), which is the reason for the invoke in the first place
So, before I figured out I needed to use the Invoke method (and, more specifically, that the scanner was working in a different thread), I was getting an error in step 6 on the line that got the TabControl.TabPages.Count.
[code]...
View 2 Replies
Sep 1, 2010
Hint: this one might sound complicated, because I am trying to give as much info as possible, but I suspect that I just want someone to tell me "yes, you are correct".On this legacy system, which dates from 2002, the user visits a web page and uses an RFID reader to read a tag number, which is then written to an input field on the web page.
The only s/w that comes with the reader is a custom DLL, nop .exe. The very sparse documentation insists that only MSIE be used and that all security relating to ActiveX be disabled.When I look into the source of the web page I see calls to functions in the DLL.Now, here's the fun part: I know zilch about ActiveX, I have to make a minor change to the DLL _but_ the VB6 source code has been lost, so I guess that I have to recreate the (seemingly very simple) DLL from scratch - this week.
Decompiling the DLL shows me the functions (locateReader, getTagVal, closeReader). However, by decompiling I can't really know the number or type of the parameters, nor the return values ... and if anyone knows the API they are refusing to share it, but basically it all seems to have been lost in the mists of time as companies went bust, were bought & sold, merged & demerged and the initial DLL might have been written by an external guy, but no one knows who.So, can I get the function params & type from the ASP page source?I see things like
Reader = new ActiveXObject("<dllName>.Reader");
Reader.locateReader();
tagVal = Reader.getTagVal();
Reader.closeReader();
I would say that none of the fn()s take parameters, that closeReader doesn't have to return anything; it looks like locateReader doesn't return anything either, so I guess that error handling will have to be in the DLL (loop forever with a popup demanding that a reader be attached; and getTagVal seems to return a string.
View 1 Replies
Nov 30, 2010
MSDN brings nothing up, so here was my attempt at a work around.
[code]...
Because event leave calls another sub i need the last active control. I have the textbox name txtTime{0} but obviously string is not a control.
So Two questions:
1) can a string value be attached to an existing control if i know it's name? Dim attControl as Control = newTime
2) All this could be avoided in event leave if i could get the left controls name. I have tried sender. tostring etc but nothing returns the textboxs name
View 6 Replies
Nov 16, 2010
I 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 Replies
Jun 1, 2010
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)'.
View 4 Replies
May 8, 2011
I have 10 PictureBox on a windows form (created in Design View) and a context menu strip is attached to each of them. I am trying to set the property of the PictureBox using the context menu.
View 1 Replies
Jan 14, 2011
On a given application form, I have around 20 controls that I need to set in the main form. I have a separate thread that only needs to ready some properties from the controls on the application form It will never try to write to the form's controls.
[Code]...
View 9 Replies
Mar 4, 2010
I have been using DBTransaction for my current projects that access a single database. However, I read some documentation on TransactionScope and was wondering in which scenario would using TransactionScope be better? Or should I be replacing DbTransaction calls with calls to TransactionScope?
View 2 Replies
Jun 27, 2011
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 Replies
Dec 9, 2011
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?
View 1 Replies
Jan 31, 2012
I show a waiting form (saying "Please wait...") on a different thread when there is long-running code in some forms (for example, during data loading). I show the form like this:
m_PopProcessingThread = New Thread(New ThreadStart(
Sub()
m_PopProcessingForm = New WaitingForm(m_Message)
Application.Run(m_PopProcessingForm)
End Sub))
[Code]...
The stack trace points to the part of code where I hide the form. How could the handle not have been created, when just before the Invoke call, I loop until said handle is created?
View 1 Replies
Oct 6, 2010
how to invoke methods, but how does one change a simple property?
For demonstration-sake, here's a very simple set of code that should help. Let's say I need to set the visible property from a child form, and thus, it needs to be invoked:
Friend Sub activateItem(ByVal myItem As PictureBox)
If myItem.InvokeRequired = True Then
????
[Code]....
View 1 Replies
May 13, 2009
i'am trying to open the autocomplete-window from a textbox without typing chars into the box.Normaly the autocompletewindow opens only if you type in a character, but this means, you have to know the first char.Is there any way to open the autocompletewindow without the first character? For example at the mouseover event of the textbox?
View 3 Replies
