C# - Stop Developers From Calling System.Windows.Forms.Application.DoEvents()?
Mar 15, 2009
We 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?
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Aug 2, 2011
I 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?
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Nov 12, 2009
Does calling the Dispose method on a Windows.Forms.Timer call it's Stop method? Or should I stop the timer before I dispose it?
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Jul 18, 2011
i 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].....
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May 18, 2010
i Have a programa that has starts in a main sub, it executes some code and after that code it opens a form using
System.Windows.Forms.Application.Run(General)
General is a form but also a class, so I wonder what it the pros or cons of using :
System.Windows.Forms.Application.Run(General)
vs
Dim gen as general
System.Windows.Forms.Application.Run(gen)
In the first I am opening a form using the name of the class, and I read that it is best to declare the instance as an object variable.
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Jun 12, 2011
i have one window application developed in VS 2005 which is running successfully on client side,My question is that now i want to convert this window application in WPF browser based application, so what should i keep in mind to convert this application to wpf applicaton, One more thing that in Window Application i have used one mdb file which contain database login detail, so on application startup this file is accessed using System.Windows.Forms.Application.StartupPath+@"/filename.mdb", now im just want to test only whether can i login to my application using WPF or not this time it give me this error "Request for the permission of type 'System.Security. Permissions. RegistryPermission, mscorlib, Version=2.0.0.0, Culture=neutral".
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Sep 8, 2010
I have the code which checks if there is a selected tab
Private Function GetBrowser() As WebBrowser
If TabControl1.SelectedTab IsNot Nothing Then
For Each c As Control In TabControl1.SelectedTab.Controls
If TypeOf (c) Is WebBrowser Then
Return c
[Code]...
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Sep 28, 2010
I grabbed an example program to modify for my needs to grab data from a Word doc and transform to XML. Right off the bat I get multiple errors. [Code] I am getting Error Type 'System.Windows.Forms.Application' has no constructors.
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Aug 23, 2010
I am adapting this code from excel vba to a Visual Studio program I am writing that will list files that are relevant to given information. I keep getting an error about filesearch not being a memeber of 'system.windows.forms.application' on line fs = Application.FileSearch, I have read and saw that I should be using the DIR function...
Sub SearchForForms()
Dim fs As FileSearch ', ws As Worksheet, i As Long
Dim SearchFileName As String
fs = Application.FileSearch <~~~ ERROR[code]....
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Mar 16, 2009
With the following imported namespaces in my project :
Imports System.Windows.Forms
Imports System.Reflection
.. I cannot add..
[code].....
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Apr 28, 2009
I have a panel with some controls in it (several textboxes, a slider, 2 buttons, and a small groupbox).. When I click a button, I want all of the textboxes within the panel to be readonly... So I have this code: [code] When I run it though, I get the following error:Unable to cast object of type 'System.Windows.Forms.Button' to type 'System.Windows.Forms.TextBox'.If I remove a button, it moves on to give me the same error but for a label..
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Apr 14, 2011
An unhandled exception of type 'System.StackOverflowException' occurred in System.Windows.Forms.dll it also says make sure you do not have infinate loop or infinate recursion il give all code in order that they are executed in Check the chechbox and it disables all irelevent stuff and populates the combobox
Private Sub CheckBox_Spray_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CheckBox_Spray.CheckedChanged
If Me.CheckBox_Spray.Checked = True Then
[code]....
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Sep 21, 2010
I 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?
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Mar 12, 2010
When I do this
Public Class cInherits : Inherits Panel
I get this: Base class 'System.Windows.Forms.Panel' specified for class 'MenuButton' cannot be different from the base class 'System.Windows.Forms.UserControl' of one of its other partial types.
How do I inherit?
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Jun 12, 2011
i need to get data from checkbox in a groupbox. in the groupbox, it also have a label. so my coding as below
[Code]...
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Jul 9, 2009
My scenario is such that I have a VB.NET project in SVN and I am using the Application Framework to start the application. This poses a great problem when different developers are working on different forms and they want to have different startup forms. Right now if we change the project settings, its changed for everyone else too. How can we work around this? Can SVN have a class committed into the repository and later changes cannot be committed into it? (more like ignoring a file but with a initial copy in the repo)
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Oct 29, 2011
I am trying to use values from form1 in my project, in form2, but Im not sure how to do it. I've tried
txtboxTotal = (Form1.vsbLength * Form1.vsbWidth) * Pattern
But I get: operator '*' is not defined for types 'System.Windows.Forms.VscrollBar' and 'Systems.Windows.Forms.VscrollBar.'
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Jan 23, 2010
Private Sub wb_Scrape(ByVal sender As System.Object, ByVal e As
[Code]...
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Oct 20, 2010
Win7 64 bit; fully patched VS2008 targeting FW2.0; VB.Net; running in Debug Mode (not tested in Release mode)I have a resonably complex app which I am refactoring a bit. As part of that, I relocated some code from a subroutine into a Click Event Handler. The Event Handler will, late in the handler, call the, reduced in function, subroutine. The point of this is thatNow when I click the button associated with the modified Handler I get:A first chance exception of type 'System.AccessViolationException' occurred in System.Windows.Forms.dll<br />With Error System.AccessViolationException Attempted to read or write protected memory.This is often an indication that other memory is corrupt.
at MusicManager2009.frmMain2.cmdLoadAlbum_Click(Object sender, EventArgs e)
at System.Windows.Forms.Control.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnClick(EventArgs e)
[code].....
All functions of the app, except those that start from the buttonclick in question, work as before in the problem version.The problem persists after rebuilding the entire solution, after restarting VS, and after rebooting the PC.
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Feb 19, 2010
When I run my project I get "An unhandled exception of type 'System.StackOverflowException' occurred in System.Windows.Forms.dll"
Public Class frmViewReport
Dim objForm As New frmViewReport
Private Sub frmViewReport_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
objForm.ViewReport("C:a2.rtp", , "@parameter1=test�mter2=10")
[code]....
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Nov 16, 2009
I have the following code running, the first time I change the selected index, everything runs smoothly. However, if I try to change the selected index again, nothing happens and the subcategories combobox values do not change.
Private Sub cboMainCategory_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cboMainCategory.SelectedIndexChanged
'* make sure the combobox is fully loaded
[code]....
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May 6, 2009
I keep getting an eroor this error says: An unhandled exception of type 'System.ArgumentOutOfRangeException' occurred in system.windows.forms.dll Additional information: Specified argument was out of the range of valid values.
Option Strict On
Public Class frmWeeklyReport
Inherits System.Windows.Forms.Form
[code].....
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Feb 12, 2011
A first chance exception of type 'System.InvalidOperationException' occurred in System.Windows.Forms.dll It displays in my Immediate Window when i run my program, I'm using a text reader to read a number of XML files using background worker...most the time it stops so something is wrong but sometimes it works fine.
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Feb 6, 2010
I am working on a card game, and i get this werid error:
A first chance exception of type 'System.Reflection.TargetParameterCountException' occurred in System.Windows.Forms.dll
The code that is cousing this error is:
Private Delegate Sub ShowcardDelegate(ByVal test As String, ByVal objtest As Object, ByVal value As Boolean)
Private Sub Showcard(ByVal test As String, ByVal objtest As Object, ByVal value As Boolean)
If objtest.InvokeRequired Then
[code].....
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Feb 23, 2009
I want to cast a system.string to system.windows.forms.form
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Jun 3, 2011
If I wanted to call the RUN prompt and the Command prompt in my application, what exe's would I need to reference?
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Jun 12, 2011
launch a Modeless Dialog I am used in me.showintaskbar property to remove application from taskmanager.but it removes the form(application)it still refreshes.How to stop the form refresh.
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Apr 16, 2010
How can any windows xp stop service application in vb.net2008?
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Mar 31, 2010
I am writing a program for my A-level coursework But for some reason I got this build error this has never occurred to me before, I have no idea why I can't use string for the name of my form.
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Mar 5, 2012
When I add a new, empty form to my VB.NET VS9 project, the linenherits System.Windows.Forms.Formis missing.What am I doing wrong here?I thought it would be added automatically.I experienced that some thing get weird if this line is not there (Form_Load is not firing, I think).
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