C# - Working Asynchronously With GUI Controls In .NET
Jun 22, 2012
I have a listbox of items that need to be processed, and I would like to process them asynchronously on a separate thread. (Never done this before).So I created a Delegate, a Callback, called the method that does the work on the listbox items.
I am getting an exception "System.InvalidOperationException": Cross-thread operation not valid: Control 'ListBoxBlah' accessed from a thread other than the thread it was created on.
Doing the asynchronous operation for individual items doesn't make sense to me because I am only doing it to perhaps perform a large number of operations (the listbox may have 20000 items) in the background while allowing the user to do other stuff.
[Code]...
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Jun 26, 2012
In my project i have moving picturebox array & if they intersect treeview will disable.& when i rightclick on the picturebox it will delete.After deleting picturebox its effects still there.When other picturebox moving on that deleted area still treeview is disabled.i used this code.
Me.Controls.Remove(a)
where a= new picturebox
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Feb 17, 2010
I often see code snippets for handling each control of a certain type on a form or panel, etc.They always start with For Each ctrl and the do a test for control type.Many .NET users are not aware, as I was not until I tried it recently, that we can LINQ on the controls collection.Below is a simple sub I created for resetting every checkbox on a panel I use as a validator.
Private Sub ResetCheckBoxes(ByRef pnl As Panel)
Dim ctrls as System.Collections.Generic.IEnumerable(Of Object)
ctrls = From c In pnl.Controls Where TypeOf (c) Is CheckBox
[code]....
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Apr 18, 2011
I want to use the following snippit.
For Each x As Control In Me.Controls
If TypeOf x Is CustomControl Then
SomeAction( x.CustomEventofCustomControl)
End If
Next
The problem here is that not all controls have event CustomEventofCustomControl, so the complier shrieks. How do I get around this.
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May 10, 2012
I've run in to a very annoying situation. At the moment I have a program with 4 forms. 3 of these forms work fine, but the fourth seems to be a dud. After clicking any one of the buttons or controls on this form it works. But if I try to click anything again, it doesn't work. I can't use my back buttons, I can't even use the minimize, maximize and exit buttons in the top right corner which are automatically built in to the program. I fear I have accidentally changed a setting, or accidentally deleted some very crucial code for this
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Jan 3, 2010
I am working on a notepad like program and I am adding tabs I've been able to successfully make buttons to add and close tabs but now all my other codes are messed up (as I was using a richtextbox before).
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Feb 1, 2011
I am trying to learn how to create Windows Forms custom controls in VB.Net by creating a .Net version of an old control I created in VB6. On this control, I have a UserControl with a Label (lblCaption), and several of the properties I add to the control should be passed to the label.This is the code I tried for the ForeColor property:
Code:
Protected mcolForeColor As Color = Color.FromKnownColor(KnownColor.ButtonHighlight)
Public Overrides Property ForeColor() As Color
Get
[code]....
When I change the ForeColor on the control in my test project, lblCaption does change to the color I selected; however, when I run the application, the label changes back to the default (button highlight) color, and the value of the property is also reverted back when I return to the form designer.What would be the proper way to implement the ForeColor property on a custom control?
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Jul 4, 2009
i'm trying to work with master pages and referencing local and master contentplaceholders. I have a master file that has this:
[Code]...
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Mar 23, 2011
I am using Visual Basic Express 2010.
I have programmatically set up a Datagrid and binding navigator etc., but I cannot get the movenext, movelast buttons to actually hook up to the Data on the Datagrid.
I have tried to set up an addhandler for the BindingNavigatorMoveLastcontrol, and although I can get the BindingNavigatorMoveLastcontrol to display my messagebox
WHICH IT DISPLAYS TWICE FOR SOME REASON I cannot get it to actually move around the Dataset, or any of the other navigation properties for that matter.
Wednesday61
Imports System.Data.SqlClient
Imports System.Windows.Forms
Imports System.Drawing
[Code].....
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Sep 25, 2009
I have used delegates multiple times over the years but for some reason this very simple code isn't working:Form has one button and on textbox. Simply trying to update the textbox from another thread and although it looks fine it's not working.[code] the parameter is being passed to the DoSomething, the UpdateTextboxText is being run and gets the correct string. But the textbox itself remains blank and I'm stumped.
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May 16, 2012
I'm trying to make a program which uses drag & drop functionality, however, it only works when I drop something onto the form, not the controls. If I do try on the controls, I just get the 'Unavailable' cursor.
The AllowDrop property is set in the properties bar, and I also set it when the form loads.
Current code:
Public Class Main
Private Sub Main_DragDrop(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles Me.DragDrop
[Code]....
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Nov 10, 2009
At work we have a pretty large web application that works by having a few pages, with lots of user controls which are nested in these pages. This is working fine most of the time but we have a problem at the moment where one of the user controls isnt working. Originally it was referenced from another project in the solution but when this wasnt working I decided to copy the file into the project and try to register it locally. It works on our development system, its only when we move it to deployment that it stops working, and I'm thinking it's something that I'm missing in the build. When you go to the page on Live the control is just missing, and no errors are generated.
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Jul 10, 2011
I'm trying to enable/disable controls inside a repeater:
<asp:Repeater ID="Repeater1" OnItemCommand="RepeaterItemCommand" runat="server">
<HeaderTemplate>
<table>
<th>
[code]....
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Mar 24, 2011
I have made a form that consists of textboxes nested in groupboxes nested in tabpages. I want to check if all textboxes are empty in every groupbox and even if the controls from a groupbox in a groupbox are empty.When they are empty i should not create an element string for my .xml document.Below is the code that I have at the moment. I call it with the form as the parameter.
Public Sub recurringControls(ByRef ctl As Control)
For Each c As Control In ctl.Controls
If c.Controls.Count > 0 Then
If c.Tag IsNot Nothing Then
[Code]...
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Feb 14, 2011
I have this code List<string> myList = new List<string>();
myList.AddRange(new MyClass1().Load());
myList.AddRange(new MyClass2().Load());
myList.AddRange(new MyClass3().Load());
myList.DoSomethingWithValues();
What's the best way of running an arbitrary number of Load() methods asynchronously and then ensuring DoSomethingWithValues() runs when all asynchronous threads have completed (of course without incrementing a variable every time a callback happens and waiting for == 3)
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Jul 23, 2010
I'm trying to make an asynchronous upload operation but I got this error message:
Error occurred, info=An exception occurred during a WebClient request`.
Here's the upload function:
Private Sub UploadFile()
Dim uploads As HttpFileCollection
uploads = HttpContext.Current.Request.Files
[code]....
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Feb 9, 2011
I've a vb.net web application where I'm referring to another vb.net dll by adding the reference of the dll and creating the object but after the call it waits for dll to finish operation and return a value before moving forward, is there a way I can do the same job asynchronously.
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Feb 8, 2011
I currently have a web application project that also includes web services within the same project. I currently have a requirement to call the web service asynchronously. Since, I haven't added the web service as a web reference within the same project, I tried to call the web service method using delegates and I see an exception "HttpContext is not available. This class can only be used in the context of an ASP.NET request" when I tried to access the Application property in my web service method call.
[Code]...
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Jun 16, 2009
In VB .NET, when you call RaiseEvent X(), is the function that handles the event X processed asynchronously or synchronously. I was under the impression that RaiseEvent and the processing of the event were Synchronous unless created explictly on another thread. I've been told otherwise though.
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Jun 23, 2010
How do i file download asynchronously in WPF vb.net?
Is there a timer control in WPF?
I am using vs2010 Pro
I need to write an app that downloads a file, uncompresses it, scroll through it and update sql table. Also print labels and invoices.
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Jun 7, 2011
I am trying to build a code to get the website asynchronously using webclient.download stringasync..I want to pass the data thus retrieved from dowloadstringcompleted to another function.[code]My problem is that I am not being able to pass on the values as StartDownload gets completed, while data is still being retrieved.
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Oct 23, 2010
[code]...
Now i need to do a few hundred/thousand requests all at the same time or atleast over a short period. I am assuning i need to do this asynchronously. I have looked all over the net and tested various ways to communicate asynchronously and am pretty stumped. None of the examples out there seem to explain how i receive the xml return as a string ("which i will write to file or db")
Does anyone have any working code to do such a process?
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Jan 7, 2011
I am trying to call this webservice asynchrounously in vb.net. So on the aspx side i added this property async="true". Now on the vb.net code side i have this function inside my webservice that i am calling.So -
dim as as webservice.webstring
as.functionasync(param1, param2)
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Feb 16, 2010
im making a transport agent for exchange and am getting hung up on how to call a method asyncronously. Im doing this based on an msdn article but like usual they didnt provide the part of the code i need to figure out.the article is in C# but i converted it to vb in my project. [URL]I know I need to setup a delegate for the method and then invoke that delegate, but im not 100% on how to implement this.
Imports Microsoft.Exchange.Data.Transport.Routing
Imports Microsoft.Exchange.Data.Transport
Namespace TestTransportAgent
[code]....
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May 17, 2010
[VS 2010 Beta with .Net Framework 3.5]I've written a C# component to asynchronously monitor a socket and raise events when data is received. I set the VB form to show message boxes when the event is raised. What I've noticed is that when the component raises the event synchronously, the message box blocks the component code and locks the form until the user closes the message. When it's raised asynchronously, it neither blocks the code, nor locks the form.
What I want is a way to raise an event in such a way that it does not block the code, but is called on the same thread as the form (so that it locks the form until the user selects an option.)
[Code]...
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Aug 31, 2011
I have working code to read an RSS feed that uses:
Dim doc As New XmlDocument
doc.Load("http://...")
Dim channel As XmlElement = doc("rss")("channel")
Dim items As XmlNodeList = channel.GetElementsByTagName("item")
Unfortunately the doc.Load call causes the rest of the program to become unresponsive until it finishes.What's the best way to perform the load asynchronously and have a callback function to process the data?Edit: Here's the code I've tried using WebClient - the Load method is still lagging:
Private Sub checkResults()
'request rss feed
Dim w As New System.Net.WebClient
[code]....
The rssReadCallback method is executed fairly quickly after calling checkResults, but then the UI freezes during the Load method.
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Feb 22, 2012
I have a flash video player embedded in a page which has javascript calls for it's controls, specifically calling playStarted() when the play button is pressed. I want to capture this event asynchronously to record when people are actually playing the video versus visiting the page, but I'm not really sure how to do this.
I was thinking the "hack" of a way would be to create a javascript function called playStarted() that would post the video ID to a separate ASP.NET page that would then record it to SQL (where I store my data on page visits and where I want to store my data on video plays.)
But ideally there is a better way to do this where I can register the javascript to the script manager so it can trigger a public sub asynchronously when it's called
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Jun 9, 2011
I need to call a stored proc from a .NET web page which takes around 15 min to process. We do not want user not to be able to browse the website in the meanwhile. Is calling it asynchronously the way to go or are there any other recommended ways?
make an asynchronous stored proc call?
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Apr 6, 2010
I have a program I would like to release, has 2 programs within it.1. The main program. 2. A resource utility.To release it, i'm going to package them both up using a 3rd party setup maker.Now, the question is this.I noticed in the snippets...theres 2 options.Update application synchronously or asynchronously.
First, whats the difference between the 2?Also, could I utilize that so it'll update from the clickonce, so I dont have to keep repackaging it?Also, I want all updates to be mandatory, vs optional like in clickonce default updates..where it gave the user the option to skip.Reasoning is, for cracks, hacks, etc, if it is modified, and i notice cracks, etc. it'll update and replace any cracks, etc. No "skip the update, so the hack/crack continues to work".
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Jun 27, 2012
I want to upload a large file of tracking numbers and process them into our ordering system.
I used to use Server.ScriptTimeout = 3000
It worked until we upgraded our servers and now it crashes.
I'm Getting This webpage is not available The connection to www.YourSite.com was interrupted.
I could see the .csv file has been uploaded, but many tracking numbers do not get processed.
I'm thinking of maybe switching to a asynchronous update. But I cannot find any good source for it.
If you have any good ideas, please let me know.
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