i'm writing for ask this community the best way for able my software not block during long operation over file multiselection.
My software analyse 1 to n PDF and for every file read all pages. for every page read all lines and for all line analyse data following string algorithm.
In case user load many PDF file the process could be long and could freeze application.
I ask to you the best way for deny freeze in my application.
On this site i read about ASYNC method or Thread sleep function and much other, but i don't understand which is best to use.
Initially i simply thought about a wait timer between file analyse, but this extend time of operation and maybe not deny freeze, which depend on CPU load and file complexity.
***** UPDATE CODE *****
Here a little schema code of my test using Async method...
Private Async Sub cmdParsePDF_Click(sender As Object, e As EventArgs) Handles cmdParsePDF.Click
Await Task.Run(Sub()
ParsePDF(textboxType.text)
End Sub)
End Sub
Public sub ParsePDF(byval intType as integer)
If textboxSource.text <>"" then
io.file.copy(textboxSource.text,textboxDestination.text,1)
'.... others operations....
End If
End Sub
...when code encounter textboxType.text or textboxSource.text and textboxDestination.text go on error because it say this object is from another thread...
How could i solve this problem ? My sub ParsePDF() have many reference to object in the form for extraction of values and count a big number of lines code... is there a way for bypass this issue ?
you can use threads :
simple example to execute sub in separate thread :
Imports System.Threading
{......}
Private Sub Button1_Click(sender As Object, e As EventArgs)
Dim BackProcess = New Thread(Sub() Me.analysePdf("d:\pdfFolder", 1))
BackProcess.Priority = ThreadPriority.Normal
BackProcess.Start()
end Sub
sub analysePdf(pdfPath as string, analyseType as integer)
'your stuff.............
'.......................
'send data to UI with invoke :
Me.BeginInvoke(Sub() textbox1.Text = "running...")
'etc...
end sub
Related
I have a VB.Net page that needs to submit data to a url after a user clicks a button. I don't need any data back from the url, I just need to pass parameters to it and allow the user to continue to the next step without waiting for the url to do it's thing.
I've seen some similar posts for c# using UploadStringTaskAsync, but haven't been able to find a corresponding method for VB.net.
https://learn.microsoft.com/en-us/dotnet/api/system.net.webclient.uploadstringtaskasync?view=net-6.0
I believe I can call the Async method from my existing nonasync methods as I don't need the response back. However, if there is a more elegant approach to do this please let me know.
Update with current code attempting to use thread:
Sub Page_Load(sender As Object, e As EventArgs)
If Not IsPostBack Then
Dim thread As New Thread(AddressOf testSub)
thread.Start()
End If
End Sub
Sub testSub
Using WC As New WebClient WC.UploadString("https://someurl.com?parameter1=testing¶meter2=anothertest", "SOMEDATA")
End Using
End Sub
This runs but unfortunately does not appear to handle any of the parameters. When I post the url directly in the browser it runs as expected. I don't need to send any data other than the querystring as well so I'm not sure if that's breaking the uploadstring. However, when I run it via debugger I don't see any errors so long as I populate that string for the data with a value.
I might be misunderstanding though when the await call is needed. While I don't need any data back, the external url can take up to 5 minutes to process. I'm wondering if it's taking too long and timing out after that thread is started.
You could run it in its own thread.
Imports System.Net
Imports System.Threading
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
' Create a thread to run this in the background
Dim t As New Thread(
Sub()
Using WC As New WebClient
WC.UploadString("https://YOURURL", "YOURDATA")
End Using
End Sub
)
' Start the thread
t.Start()
End Sub
End Class
I am currently working on a VB.NET form that automatically create Word documents according to an Excel file and a few extra data asked by the form (Project Name, Customer Name, Use SQL, ...).
This procedure works fine and takes approximatelly 1 or 2 minutes to complete.
The issue is that all my script is in ButtonGenerate.Click Handler. So when the Generate button is pressed the form window is bricked and it's impossible to Cancel...
It shouldn't be in a Click handler. Opening a new thread for that long task seems better. But Multithreading isn't very familiar to me.
I tryed launching the script with
ThreadPool.QueueUserWorkItem(...
but my Generate Sub sets labels and update a Progress Bar in the main form, so I doesn't work unless I use
Me.Invoke(New MethodInvoker(Sub()
label.Text = "..."
ProgressBar.Value = 10
' ...
End Sub)
each time I need to update something on the form and I can't even retrieve any new push of a button with that (A cancel button would be nice).
This is basically my code :
Public Class TestFichesAutomation
Private Sub BtnGenerate_Click(sender As Object, e As EventArgs) Handles BtnGenerate.Click
System.Threading.ThreadPool.QueueUserWorkItem(Sub() Generate())
End Sub
Public Sub Generate()
' Check user options, retrieve Excel Data, SQL, Fill in custom classes, create Word docs (~ 1 minute)
End Sub
So How would you handle that script ? Is Threading even a good solution ?
Thanks a lot for your help ^^ and for the useful doc.
My app now open a new thread and uses 2 custom classes to act like buffers :
Private Async Sub Btn_Click(sender As Object, e As EventArgs) Handles Btn.Click
myProgress = New Progress
' a custom class just for the UI with the current task, current SQL connection status and progress value in %
_Options.ProjectName = TextBoxProjectName.Text
_Options.CustomerName = TextBoxCustomerName.Text
...
' Fill in a custom "_Options" private class to act as a buffer between the 2 thread (the user choices)
Loading = New Loading()
Me.Visible = False
Loading.Show() ' Show the Loading window (a ProgressBar and a label : inputLine)
Task.Run(Function() Generate(Progress, _Options))
Me.Visible = True
End Sub
Public Async Function Generate(ByVal myProgress As Progress, ByVal Options As Options) As Task(Of Boolean)
' DO THE LONG JOB and sometimes update the UI :
myProgress.LoadingValue = 50 ' %
myProgress.CurrentTask= "SQL query : " & ...
Me.Invoke(New MethodInvoker(Sub() UpdateLoading()))
' Check if the task has been cancelled ("Cancelled" is changed by a passvalue from the Loading window):
If myProgress.Cancelled = True Then ...
' Continue ...
End Function
Public Shared Sub UpdateLoading()
MyForm.Loading.ProgressBar.Value = myProgress.LoadingValue
MyForm.Loading.inputLine.Text = myProgress.CurrentTask
' ...
End Sub
You should look into using the Async/Await structure
if the work you need to do is CPU bound, i like using Task.Run() doc here
By making your event handler Async and having it Await the work, you prevent the UI from locking up and avoid the use of Invoke in most cases.
ex:
Private Async Sub Btn_Click(sender As Object, e As EventArgs) Handles Btn.Click
Dim Result As Object = Await Task.Run(Function() SomeFunction())
'after the task returned by Task.Run is completed, the sub will continue, thus allowing you to update the UI etc..
End Sub
For progress reporting with Async/Await you might be interested in this
I'm new to multi-threading, so I need a general guidance how to proceed.
In a nutshell, I need to call an external webservice thousands of times per second. The response is roughly 1 second per record, which does not work well if I have a million of records to send. So, I've been tasked to use multi-threading to open multiple threads (the number is controlled dynamically) to simultaneously call WS. So, if I can open 100 threads that call WS simultaneously, the task should finish much faster... in theory.
Code is at the bottom, I've cut a lot of unnecessary pieces out of it so please let me know if something makes no sense
The idea behind this code is you would call in Threads.Process, pass DataTable with data that needs to be sent out via WS. This process would run until we processed all records in the data table and _threads (which holds a list of background objects currently working) has zero items in it.
StartThreads would instantiate new background objects if number of simultaneous threads permits and there is new data to be worked on. When a background object completes its task, in order to pass data back to the static object to log its data, it calls Threads.ThreadFinished and passes itself as parameter at which point logging info would be recorded and backgroundobject is removed from _threads.
However, during my testing I noticed that threads are overlaping when calling Threads.ThreadFinished, I tried to offset it with SyncLock to keep it thread safe, but it still does not work 100% fool proof (probably because there are other shared functions still not protected). Since I don't understand this threading very well, I have a feeling there is an easier way of doing this. So, am I on a right track? Should I keep going or switch to a different method? I've researched other multi-threading methods like ThreadPool, but I ended up with this method.
Public Class Threads
Public Shared Sub ProcessRecords(ByVal dt As DataTable)
_threads.Clear()
_startTime = Now
_dt = dt
While Working()
StartThreads()
Thread.Sleep(100)
End While
End Sub
Private Shared Sub StartThreads()
While _threads.Count < Settings.NumberOfThreads AndAlso _rowCounter < _dt.Rows.Count
Dim id As String = GetRandomChar(, 20) ' Generate a random ID for logging purposes
Dim tw As New ThreadWorker(_dt.Rows(_rowCounter), _rowCounter, id, _dt.Rows(_rowCounter)("id").ToString())
_rowCounter += 1
_threads.Add(tw)
End While
End Sub
Public Shared Sub ThreadFinished(ByVal tw As ThreadWorker)
SyncLock tw
Log(tw.Log)
_threads.Remove(tw)
End SyncLock
StartThreads()
End Sub
Private Shared Function Working() As Boolean
Return _rowCounter < _dt.Rows.Count OrElse _threads.Count > 0
End Function
End Class
Public Class ThreadWorker
Private _bw As System.ComponentModel.BackgroundWorker
Private _logDebug As New StringBuilder
Sub New(ByVal dr As DataRow)
_bw = New System.ComponentModel.BackgroundWorker
_bw.WorkerReportsProgress = True
_bw.WorkerSupportsCancellation = True
AddHandler _bw.DoWork, AddressOf bw_Working
AddHandler _bw.RunWorkerCompleted, AddressOf bw_RunWorkerCompleted
_bw.RunWorkerAsync()
End Sub
Private Sub bw_Working(ByVal Sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs)
' Call webservice ...
_logDebug.AppendLine("Response from WS")
End Sub
Public Sub bw_RunWorkerCompleted(ByVal Sender As Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs)
_logDebug.AppendLine("Job completed")
Threads.ThreadFinished(Me)
End Sub
End Class
EDIT 1:
I think I've solved an issue with threads getting 'lost' - basically I have to SyncLock _threads in all Shared functions (SyncLock tw doesn't seem to do it's job). Still, this feels dirty and hacky at best. I feel like there is a better way to do things. I am currently looking into ThreadPool method, but I am a bit put off by its number of thread limits. I will potentially need to open thousands of threads.
What else I noticed is that the more concurrent threads I open, the longer it takes to get initial response from the WS. For example, if I work 1 record/thread at a time, it takes 1 second to get a response from WS. If I open 100 threads, it takes up to a minute to get a response. I suspect networking is buckling here, or maybe its a windows limitation?
I'm working on a simple VB.NET program (just using winforms) and am really terrible at UI management. I'd like to have a single button that starts a process, and then have that same button stop the process.
I'm thinking about having the main form initiate a counter, and the Click event iterate the counter. Then it does a simple check, and if the counter is even it will do thing A and odd does thing B.
Is there a better way, aside from using two buttons or stop/start radio buttons?
I've done that exact thing one of two ways. You can use a static variable or toggle the text of the button.
Since your button has two functions, Good design requires you to indicate that to the user. The following code assumes the Button's text is set in Design Mode to "Start", and the code to start and stop your process is in the Subs StartProcess and EndProcess.
Public Sub Button1_Click(ByVal Sender as Object, ByVal e as System.EventArgs)
If Button1.Text ="Start" Then
StartProcess()
Button1.Text="End"
Else
EndProcess()
Button1.Text="Start"
End IF
End Sub
EDIT
The above solution is fine for a single-language application developed by a small number of developers.
To support multiple languages, developers typically assign all text literals from supporting files or databases. In larger development shops, with multiple programmers, using a display feature of the control for flow-control may cause confusion and regression errors. In those cass, the above technique wouldn't work.
Instead, you could use the Tag property of the button, which holds an object. I would typically use a Boolean, but I used a string just to make more clear as to what's going on.
Public Sub New()
'Initialize the Tag
Button1.Tag="Start"
End Sub
Public Sub Button1_Click(ByVal Sender as Object, ByVal e as System.EventArgs)
If Button1.Tag.ToString="Start" Then
StartProcess()
Button1.Tag="End"
Else
EndProcess()
Button1.Tag="Start"
End IF
End Sub
This is example in pseudo-code. I don't guarantee that names of methods and event are exactly match real names. But this should provide you a design that you could use for responsive form.
Lets say, your process is running on separate tread, using BackgroundWorker.
You setup your worker and start process
Class MyForm
private _isRunning as boolean
private _bgWorker as BackgroundWorker
sub buton_click()
If Not _isRunning Then
_isRunning = true;
StartProcess()
Else
StopProcess()
End if
end sub
sub StartProcess()
' Setup your worker
' Wire DoWork
' Wire on Progress
' wire on End
_bgWorker.RunWorkerAsync()
End sub
sub StopProcess()
if _isRunning andAlso _bgWorker.IsBusy then
' Send signal to worker to end processed
_bgWorker.CancelAsync()
end if
end sub
sub DoWork()
worker.ReportProgress(data) ' report progress with status like <Started>
' periodically check if process canceled
if worker.canceled then
worker.ReportProgress(data) ' report progress with status like <Cancelling>
return
end if
' Do your process and report more progress here with status like <In Progress>
' and again periodically check if process canceled
if worker.canceled then
worker.ReportProgress(data) ' report progress with status like <Cancelling>
return
end if
worker.ReportProgress(data) ' report progress with status like <Ending>
end sub
sub ReportProgress(data)
if data = <some process state, like "Started"> then
btnProcess.Text = "End Process"
end if
End sub
sub ReportEndOfProcess
btnProcess.Text = "Start Process"
_isRunning = false
end sub
End Class
Here you can pinpoint the names of methods and events
You have to substitute identifiers with real names and create you state or data object, which will carry information from background thread to UI thread, and also an Enum Status that can be part of your custom state object. This should work once translated into real code
Just want to show another approach for this task
Use .Tag property for your own purpose
If .Tag Is Nothing (by default in designer) then start process
If not Nothing -> stop process
Public Sub Button1_Click(ByVal Sender as Object, ByVal e as System.EventArgs)
If Me.Button1.Tag Is Nothing Then
StartProcess()
Me.Button1.Tag = New Object()
Me.Button1.Text = "End"
Else
EndProcess()
Me.Button1.Tag = Nothing
Me.Button1.Text = "Start"
End
End Sub
I'm not a VB coder but I'm tinkering with a little VB.net utility project which lets you set up a few parameters in a form and hit "go" - this then does a lot of logic which can run for several minutes.
This all happens in the go-button-handler which blocks the form. I wondered, is it easy in vb.net to make all this logic happen in a separate thread which can still update the form i.e. update a label to show which file is being processed? If it's complicated, it's not worth doing in my use-case!
Is it possible to just copy-paste my event code into a thread.Run or something like that, or even dynamically create a thread class around the code I have?
I have used the BackgroundWorker class (System.ComponentModel.BackgroundWorker) many times for things like this. It's very simple to use (compared to other multi-threading techniques available in .NET). Just drag it from the tool box onto your form, for example. If you set it's "WorkerReportsProgress" and "WorkerSupportsCancellation" properties to "True", you can even give feedback in your UI in the form of a progress bar, for example, and provide the ability for the user to click the cancel button.
Anyway, there's a lot more information about it than I can reasonably include here, so I would start by looking at this page:
http://msdn.microsoft.com/en-us/library/system.componentmodel.backgroundworker.aspx
BackgroundWorker is a good choice to start. Whatever you use be aware that performance can be affected if the background thread is processor intensive i.e. a long running tight loop. This might not be very obvious if you have a multi-core CPU.
Here is a simple example of Threading.Thread.
Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
Button3.Enabled = False
'for example pass a string and an integer to a thread as an array
Dim params() As Object = {"one", 1} 'parameters for thread. object picked because of mixed type
Dim t As New Threading.Thread(AddressOf someThread)
t.IsBackground = True
t.Start(params) 'start thread with params
End Sub
Public Sub someThread(params As Object)
'not on the UI
Dim theparams() As Object = DirectCast(params, Object()) 'convert object to what it really is, an array of objects
Dim param1 As String = DirectCast(theparams(0), String)
Dim param2 As Integer = DirectCast(theparams(1), Integer)
Debug.WriteLine(param1)
Debug.WriteLine(param2)
showOnUI(param1)
End Sub
Public Sub showOnUI(s As String)
If Me.InvokeRequired Then
'not running on UI
Me.Invoke(Sub() showOnUI(s)) 'run method on UI
Else
'running on UI
Label1.Text = s
Button3.Enabled = True
End If
End Sub