How To Cancel BackgroundWorker In WPF Without DoEvents
Jun 2, 2011I have a search box that works great in WinForms, but is giving me trouble in WPF.
It works by starting a search each time a letter is pushed, similar to Google.
[Code]...
ADVERTISEMENT
Cancel Backgroundworker - Got The Error Message" This BackgroundWorker Is Currently Busy And Cannot Run Multiple Tasks Concurrently?
Dec 14, 2009in my button click event i ececure
If BackgroundWorker4.IsBusy Then
BackgroundWorker1.CancelAsync()
End If[code]....
after proceess completed if press the button again.i got the following error msg
This BackgroundWorker is currently busy and cannot run multiple tasks concurrently.
Call Same BackgroundWorker Multiple Times Without Using Application.DoEvents
Mar 4, 2010I'm running in to a problem that I was able to fix with Application.DoEvents, but don't want to leave that in because it might introduce all sorts of nasty problems. Background: Our app is primarily a desktop app that makes many calls to a web service. We control everything but changes to the overall system design are not going to be seriously considered. One of those calls, Calculate, is used very often, and occasionally can take a few minutes to process all the data to return valid results.
[Code]...
Signal (NOT Cancel) A BackgroundWorker?
Mar 7, 2011Is it possible to send information to a BackgroundWorker thread while it is running? Here is my scenario: Parent thread calls background thread to send a data request to a database. If it's a big complicated query it can take a while for the db to respond, so putting the db request on the background worker thread is great. My app can do other stuff while the one thread waits for the db.
Now, db responds with beginning of data. I want my background thread to report back meta data about the result set to the parent thread. No problem there, I can use a custom user state object and the ReportProgress method. But now, how to I send a signal from the parent thread back to the worker thread? I want the background thread to wait while the parent thread does something, and then tells the worker thread to keep going or quit. I know how to cancel a background thread, but I want the parent to be able tell the child some information other than "cancel". Here's one way to think about it:
[Code]....
Cancel Current BackgroundWorker Task Before Running Again?
Aug 1, 2010I'm using a BackgroundWorker to perform some analysis on a separate thread. The BackgroundWorker is called when a user clicks a CheckBox.
I need to provide for the user clicking the CheckBox, starting the BackgroundWorker task, and then changing their mind and clicking the CheckBox again.I simply want to cancel the currently running task and set the analysis off again. Currently I have the following method:
Public Sub UpdateParkStatusAsync()
Try
'Debug output.
Console.WriteLine("UC_Map_ViewModel.UpdateParkStatus called.")
[code]....
Cancel Validating In A DataGridView When A User Clicks The Cancel Button?
May 18, 2006I validate a DataGridView with the CellValidating-eventhandler.That works fine. However, I want to avoid validating when the user presses the Cancel button. In the sequence validation occurs before the event CancelButton.Clicked.
View 1 RepliesCancel Save Event - E.cancel
Sep 21, 2011i want to do this: when user click save button, the form must be check first..
if user did not insert the required data, user are not allow to save form..
the code:
Private Sub AssetMasterBindingNavigatorSaveItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles AssetMasterBindingNavigatorSaveItem.Click
[Code].....
VS 2010 E.cancel "cancel Is Not A Member Of "System.EventArgs" Error
Mar 13, 2011Im coding an interest rate calculator and I need a close clause for the textbox and the combo box using e.cancel and im getting a "cancel is not a member of "System.EventArgs" error
View 13 RepliesWhat Can Use In Replace Of The DoEvents() In Vb6
May 23, 2005I am using ASP.NET and was wondering what i can use in replace of the DoEvents() in vb6?
View 5 RepliesWhat's The Equivalent Of The VB6's DoEvents In .NET
May 4, 2009What's the equivalent of the VB6's DoEvents in .NET?
EDIT:I have a Sub that takes a long time to do its work. (it has a do-while) when I call it, The form turns white. in VB6 I used to put a DoEvents in the method (inside its do-while) to prevent this.
Application.DoEvents Alternative?
Jun 6, 2011Any good alternative to using DoEvents in VB.NET
View 6 RepliesVS 2010 AccessViolationException - .DoEvents
Apr 9, 2011I have a simple loop that "sleeps" a thread..Out of nowhere i will get this error below, it could be 1 minute, 20 seconds, 5 seconds, all at random times...how to fix it?
View 7 RepliesApplication Hangs On Call To Doevents?
Dec 22, 2010I am re-posing this question because the prior post has gotten really full of side issues so I fear the main problems has been lost.I have a windows forms application written in VB.NET which scrapes information from serveral web pages? I am having problem with one particular site where partway through the page navigation my application hangs. When I press pause (or break) in the debugger, it stops on a call to System.Windows.Forms.Application.DoEvents.
View 7 RepliesCommand Of DoEvents In Program 2008?
Mar 16, 2009What is the command of DoEvents in VB2008?
in VB6 when I was doing a loop I wrote DoEvents in the loop to continue with other events.
Does DoEvents Affect Only Current Thread?
Jun 7, 2011I have a simple 'Working' form that runs on its own thread to keep the user informed that the application hasn't died during long running operations. In order to get the working form to update I had to insert a DoEvents() call. I'm curious, will this only pump messages for the current thread I'm in, or will it do it for the whole application? I would prefer that the main window stay unresponsive till the operation finishes. Just to be clear, I'm fine with the code I have, but I would like to know how DoEvents() behaves with threads.
Below is the code for the working form.
Public Class frmWorking
''' <summary>
''' Creates and starts a new thread to handle the Working Dialog
''' </summary>
''' <returns>The thread of the Working dialog.</returns>
[Code] .....
Exit Out Of Application.DoEvents() Loop?
Dec 15, 2009how to exit out of the Application.Do() as i am hanging in that .Here is a sample of my code.
Imports PDFCreator
Imports System.Windows.Forms
Public Class Form1
[Code]....
Hooking In To Application.DoEvents Method
Jul 25, 2009I am not very familiar with VB.NET so I don't know if this is possible.Some code I am working on is setting the properties of a very large class. In the setter of each property an event is raised to indicate that the class data has changed. An event handler then serializes the instance of the class to a database.Obviously I do not want this to happen after each property is set, so I need to either have a delay before saving, or something else.I am keeping a large list of instances in a cache implementation already, so one option would be to only process the cache every now and then and save all unsaved instances in cache to the database.So I tried to see if I could derive a class from Application (and override DoEvents), but it is NotInheritable, so no luck there.
View 3 RepliesNet Not Responding, Application.DoEvents And Threading?
Mar 8, 2009My mdi VB.Net application performs a long operation on some data. Ideally I should use a separate thread to prevent the dreaded "Not Responding" message.My problem is if I use a separate thread users then have the ability to click on other controls in the application which can directly affect the operation my background thread is working on, creating an error.
Is there any way to prevent all the mdi windows, toolbars and other controls from receiving mouse clicks and keyboard input during my background thread's operation?
Or is there a way to clear the message que before performing a Application.DoEvents?
VS 2008 Unable To Use An Application.DoEvents?
Dec 11, 2009I have a unique situation in that I've developed a VB.NET application for AutoCAD. The way this works, you build your project into a dll and utilize AutoCAD API references when designing the project. From AutoCAD, a "Netload" command will load your dll into it's namespace to run. AutoCAD then essentially takes ownership of your application from here on out. The application is ran using a command defined in a method's attribute:
<CommandMethod("CommandNameForApp")>Public Sub MyCommand()
'Code Here
End Sub
Due to the heavy load of processing loops as it evaluates AutoCAD drawing data, processes this data, and generates many, many Excel reports, I've added a boolean property called Cancelled to my Progress class. When the user cancel's the process, this is seen by the process and further evaluation is ended and everything is cleaned up nicely. In order for this to work though, I have to implement Application.DoEvents. Without it, the Cancel feature will not work at all. With it, now instead of allowing the application to stay loaded, the Command method is fully closed.I have added a go-to point and simply verify that the application isn't closing because of a user-cancellation event. Here's what it looks like now:
<CommandMethod("WireShop")> Public Sub WireShopApplication()
'Initialize Configuration File Data
'Initializes ValidBlocks, MarginDistance, WindowDistance, and HelpFileName Properties
If ConfigurationFileInitialization() = False Then Exit Sub
[code].....
In my opinion, this seems a little hokey. However, I'm not that familiar with exactly what Application.DoEvents is doing in the background to understand how to "head it off at the pass".
Application.doevents() Causing Some Sort Of Overlap?
Nov 9, 2009I'm trying to automate the process of logging into twitterfeed.com, and filling in the information (the feed url and twitter username are pulled from textboxes). I had it mostly working the other day, even if it is a bit sloppy (the only way I could get one button to click is to send 50-some tabs). However, lately it seems to enter in a sort of loop. When I pause the program, Visual Studio indicates that it is the Application.DoEvents in the Private Sub "wait" that is still running even after it should be.
Public Class Form1
Private feed, username, temp As String
' Code stolen off of a website as an alternative to sleeping, or trying to do a timer + while combo like I had been doing
[Code].....
Getting An Applications.DoEvents Event To Function Properly?
Nov 21, 2010I'm having trouble getting an Applications.DoEvents event to function properly. VB keeps telling me I dont have a valid argument. Can anyone look at this and explain how I would complete the expressiojn for Application.DoEvents.
[Code]...
VS 2010 An Extra Click To Get Out Of A While Loop Using .DoEvents() ?
Mar 15, 2012I wrote a small API gui to communicate over foundation fieldbus.I've used a While loop that constantly reads some parameter values from the bus. At the end of the While loop, I put Application.DoEvents()so that I can use another button to stop the reading process. It all seems good and easy.. but there's one problem: when I get the While loop running and wish to stop the process, I have to first click somewhere on the form, anywhere, before I could click any buttons(either 'stop reading' or 'reset' button mostly). That extra click makes my form seem unresponsive and lame.I wonder whether this is a problem pertaining to DoEvents() or my use of Foundation fieldbus.
View 1 RepliesCalling DoEvents From Inside Custom Control Library
Sep 21, 2010I have a custom control's library. Now there's a control which looks like a panel, and when it opens up I want to animate its vertical growing like this:
For h As Single = 0 To finalHeight Step 0.5
Me.Height = CInt(h)
' HERE I WANT TO CALL DoEvents'
Next
Me.Height = finalHeight
If I don't call DoEvents in the loop then the animation is not shown, I only get the final height without a visual feedback along the way. I can call DoEvents from inside my main WinForm project, but can't inside a library. How can I do that, without drowning into the deep threads waters?
Forms :: DoEvents Or Update GUI While Database Query Is Running
Aug 11, 2011I have an application that performs database queries using "Imports System.Data.SqlClient". I want to display an animated GIF on the taskbar which spins while the query is running. However, during a query the application simply hangs and does not update the GUI until the query has finished, at which point the spinning icon is set to invisible anyway. Is there any way to force the GUI to update while the query runs?
View 2 RepliesBackgroundworker Inside Another Backgroundworker?
Apr 2, 2012i'm in the need to start a backgroundworker inside another one.Now...The first one BGW starts a for cycle, and inside this one there is the second BGW that has to upload an image to a server.The trouble is that, the progress event and the complete event of the internal BGW are never called.
View 11 RepliesC# - Stop Developers From Calling System.Windows.Forms.Application.DoEvents()?
Mar 15, 2009We just spent 300 man-hours fixing a buggy application in the field. It all came down to calling Application.DoEvents (re-entrancy problem).This was not caught in design reviews, code reviews.The code was inserted two years ago with the first version; the application was always "flaky" but recent changes exposed the re-entrancy problems to a greater degree. This incident is the second time in our organization that Application.DoEvents caused failures and multi-man hours of debugging.It was discovered in this case by simply noticing the call,buried way down in a complex event handler for an asynchronous task.What do you suggest to prevent this issue from happening again:
Add checkin gates to source control?
Developer training?
Code Analysis rules (why is this not already a built-in rule?)
How to I enforce a coding practice?
Application Does Not Return From Call To System.Windows.Forms.Application.DoEvents?
Aug 2, 2011I have a windows forms application written in VB.NET which scrapes information from serveral web pages (who doesn't right)? Anyway, I am having problem with one particular site where partway through the page navigation my application hangs. When I press pause (or break) in the debugger, it stops on a call to System.Windows.Forms.Application.DoEvents.
Resuming execution shows that it really is stuck on this line (it does not reach the next line of code). It also hangs about the same point each time I run it (at least its consistent). Since System.Windows.Forms.Application.DoEvents yields to other threads on the same processor and then resumes execution of the current thread, I think the problem is that some other thread is not behaving well (not returning from some event handling code). I thought Windows 7 was pre-emptive, which makes me
doubt that theory but I really don't know.
[Code]...
The program scrapes somewhere between 12 and 14 pages before it gets stuck on the call to DoEvents. Does anyone have a clue why this would happen? Why would any call to DoEvents hang?
Application.DoEvents() Function Halt And Crash Application In Windows Vista
Jul 18, 2011i made an application for serial communication. for this application i need to set delay time. during this delay time i m doing some other task. So for those task i need to take back control from delay function, for this purpose i am unsing Doevents() function.Its work fine On other OS (XP, Windows7 32/64-bit). But Application.DoEvents() function halt and crash in windows vista.
Private Sub TimeDelay(ByVal DT As Integer)
Dim StartTick As Integer
StartTick = Environment.TickCount()
[Code].....
DoEvents Returns "Value Cannot Be Null." Error?
Dec 6, 2003Code:
Application.DoEvents()
Error:
[code].....
Perform "DoEvents" On A Conditional Basis?
May 31, 2010Several months ago, I asked someone here if it was possible to perform "DoEvents" on a conditional basis. This was for a VB6 application and it worked okay. It will not work in VB2010 and I was wondering if someone could tell my why?Error Message from VB 2010:
A call to PInvoke function 'MyApp.frmMain::GetQueueStatus' has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature. Check that the calling convention and parameters of the PInvoke signature match the target unmanaged signature.
[Code]...