Use BeginInvoke To Ensure That A Second?
May 20, 2009
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.
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Oct 22, 2010
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].....
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Dec 1, 2011
instead 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]....
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Jul 25, 2011
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.
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Sep 5, 2010
where is the best place to learn InvokeRequired and BeginInvoke.
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Mar 1, 2011
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.
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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.
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Mar 26, 2012
I 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?
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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]
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Feb 1, 2010
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?
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Jun 9, 2011
I 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?
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Apr 28, 2010
i am using wpf,vb,vs2008,.net framework3.5, in my application i am trying to show one progress dialog during the calculation done in backend.so i am running progress dialog and then in a new thread i am executing the calculation operation using dispatcher.begininvoke(priority normal). in this dispatcher operation i want to update the progress dialog .if i am trying to do somethimg then that update after the completion of dispatcher operation only .i want to show the message in mean time.
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Feb 26, 2010
i am using wpf,vb,vs2008,.net framework3.5, in my application i am trying to show one progress dialog during the calculation done in backend.so i am running progress dialog and then in a new thread i am executing the calculation operation using dispatcher.begininvoke (priority normal). in this dispatcher operation i want to update the progress dialog .if i am trying to do somethimg then that update after the completion of dispatcher operation only .i want to show the message in mean time.
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Mar 5, 2009
i 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]...
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Jun 11, 2011
Say if you had two private subs on a form, how do you ensure the first sub called has completed it task before the second is run.
[Code]...
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Feb 20, 2010
I have a problem with ensuring no duplicates. I have an Appointments form (frmAppointments) and within it exits 4 date time pickers. The first 2 date time pickers are dedicated to creating an appointment date whilst the other 2 are for the purpose of changing an existing appointment date. When the date and time is entered into either one of the pairs (of date time pickers), the values inside get transferred to 2 corresponding textboxes. The user then clicks Save (btnSave) and the values are saved to sql.
How can I ensure no duplicates (of the date and time) can be created?
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Jul 11, 2010
How can I ensure that a user enters data in one text box before being allowed to move on to the next text box Example I have four text boxes the user can enter a grade in. I want to lock the other three box until the user has entered a number in text box 1. Once a valid number has been entered in text box 1, that releases or enables text box 2. Once a valid number has been entered in text box 2, that releases or enables text box 3. And once a valid number is entered in text box 3, that releases or enables text box 4.
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Feb 3, 2011
So when that code run the program don't switch.Say I want to
Open a file
Write something
Close a file
Way when I open a file, another thread want to open that same file. That means open a file get executed twice.
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Sep 30, 2011
I have a screencasting program where it takes 10 screenshots every second and saves it to a temporary directory then through ffmpeg the series of images are compiled into a video format. My problem is that due to the computers processing power or the size of each screenshot and its quality it sometimes takes longer than 100 Milliseconds to create one causing the whole video to be off balance. How can I ensure 100% that 10 Images will be stored?
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Sep 2, 2010
I've created some classes that will be used to provide data to stored procedures in my database. The varchar parameters in the stored procs have length specifications (e.g. varchar(6) and I'd like to validate the length of all string properties before passing them on to the stored procedures.
Is there a simple, declarative way to do this?
I have two conceptual ideas so far:
Attributes
public class MyDataClass
{
[MaxStringLength = 50]
[Code]....
This seems like a lot of work and will really make my currently-simple classes look pretty ugly, but I suppose it will get the job done. It will also take a lot of copying and pasting to get this right.
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Feb 10, 2010
I have a WCF service being hosted in a Windows Service (using techniques discussed here) and it works great. I'm now writing a (VB.Net) frontend app that needs to call that service, but I don't want my users having to fiddle around with the services snap-in and starting the service manually. Can I write some code to ensure the Windows Service is started, or start it if it isn't?
Edit: OF course, I can ensure the Service startup is set to automatic, but it doesn't need to be running all the time, and even then the frontend app still needs to be sure the service is running and start it if it isn't.
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Sep 8, 2009
I need to make sure that the connection to a POS printer is successful before writing data to the database and then printing a receipt. The POSprinter is normally of type BTP 2002NP but may differ. The common thing is that they are all connected via COM-port and NOT usb, so no drivers installed at all on the client. Can I send some kind of "ping" on a COM-port and check if a device is connected and turned on? Additional information, the application is developed in VB.net and Visual Studio 2008
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Sep 5, 2008
how to ensure that a process created via the diagnostics.process class goes away when my app does. My app starts two processes, one runs plink and one runs psftp. Due to reasons that I don't want to become the focus of this post it is possible that my app will shutdown in an ungraceful manner. When this happens the psftp process dissapears but the plink process remains left behind. See the code below for how I am creating these processes.
Code:
Public Sub New()
Try
p = New Diagnostics.Process
'p.StartInfo.FileName() = "plink"
[code]....
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Oct 6, 2011
Please take a look at the code below. I was told by the individual that developed itoriginally that the code only adds the rows of data the user entered. In other words,there 5 rows of textboxes. user can enter data into one row or into all 5 rows. If the user enters data into one row of textbox, that's what gets inserted into the db.I made some minor change to the code so that users can tell when a payment is made by check or cash payment.Since I made that change, whether a user enters data into one row or all 5 rows, all 5 rows get inserted into the db.How can I modify this code to ensure only rows entered get inserted?
For x = 1 To 5 Step 1
dedval = obr.FindControl("ded" & CStr(x))
chckvalflag = obr.FindControl("chck" & CStr(x))
[code].....
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Mar 10, 2011
I have the following code which is part of a PA Call system: The 'SetPTT' nd 'DisableZones' statements set controls on the form where the code is. The LAPG2Coms.SetZones command starts another project within the solution to control an external controller. What I can't understand is why it executes the LAPG2 statement before SetPTT or DisableZones. The LAPG2 statement for messages is in the PlayMessage Procedure
[Code]...
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Nov 25, 2011
I need to ensure that the user can only click the button (to acknowledge the message) and not do anything else (like clicking another button). How can I do that?
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May 8, 2011
I'm trying to find out how to ensure a font is found by a project.I would expect to be able to add it (Them) to the recourses but can't find how to do that.When I get to 'Add item' I've tried 'New' and 'Existing' but can't find a template for fonts, so I'm lost (again).
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Mar 6, 2012
I have a listbox that is sorted and the data table that is bound to it is also sorted. I am trying to add a Record to this data table and ensure that it is always at the end of the list. Is there a way to do this using specific character combination?
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May 7, 2009
I need to ensure 2 calls are enlisted in a transaction
[Code]...
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Sep 24, 2009
I've written a small program that monitors the customer field in Quickbooks and query's a database to determine if there are any important notes for the selected customer. This works fine however, I either need the messagebox or a form to come to the front of all open windows on the system to inform the user that the selected customer needs to be reviewed.
How can I ensure that a form (or messages box) that opens in my program comes to the front of any and all application windows that are open?
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