Loop through each item in Listbox and load a webpage - vb.net

I'm trying to load a new webpage through the control webview2 in .net6+ windows forms, and I'm using a listbox to extract any single item and add it to the url to load on webview.
For example in listbox I have:
11
22
33
44
55
I would like at the press of a button that a loop starts to load one by one,each of these items like
WebView21.Source = New Uri("https://google.it" & ListBox1.Items.first & "rest of the url")
and after the webpage is loaded, it s supposed to extract it's html to check if a certain string is present with
Dim html As String
html = Await WebView21.ExecuteScriptAsync("document.documentElement.outerHTML;")
If html.Contains("Not found") Then
MsgBox("In Vacanza")
Else
MsgBox("Attivo")
End If
End Sub
after that, it goes back to the second listbox item, load the webview, check the html and so on.
My question is how can I loop the WebView in order to pick each of the items one by one and to proceed to do these little things in the while?
p.s. Once the loop arrives to the last listbox item, would it be possible to start it again from the first item?
Much thanks
edit1:
I'm trying with
Private ReadOnly resetEvent As New ManualResetEvent(False)
Async Sub scanWeb()
For Each listBoxElem As String In ListBox1.Items
resetEvent.Reset()
AddHandler WebView2.CoreWebView2.NavigationCompleted, AddressOf OnNavigationCompleted
WebView2.Source = New Uri("https://ikalogs.ru/tools/map/?page=1&server=22&world=10&state=active&search=city&allies%5B1%5D=&allies%5B2%5D=&allies%5B3%5D=&allies%5B4%5D=&nick=" & listBoxElem & "&ally=&island=&city=&x=&y=")
Await Task.Run(Sub() resetEvent.WaitOne())
RemoveHandler WebView2.CoreWebView2.NavigationCompleted, AddressOf OnNavigationCompleted
Dim html As String
html = Await WebView2.ExecuteScriptAsync("document.documentElement.outerHTML;")
If html.Contains("Not found") Then
DataGridView1.Rows.Add(listBoxElem, "IN vacanza")
Else
DataGridView1.Rows.Add(listBoxElem, "Attivo")
End If
Next
End Sub
Private Sub OnNavigationCompleted(sender As Object, e As CoreWebView2NavigationCompletedEventArgs)
resetEvent.Set()
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
WebView2 = New WebView2()
WebView2.EnsureCoreWebView2Async()
End Sub
but it seems the loop doesn't wait for the process to end and it goes straight to the next listbox item...

best way is to enumerate listBox items in a for-each loop : (I added an escape way -simple mouse clic on form - to quit loop)
Dim wStop As Boolean
sub scanWeb()
Do
For Each listBoxElem As String In ListBox1.Items
WebView21.Source = New Uri("https://google.it" & listBoxElem & "rest of the url")
'etc....
Next
Loop Until wStop = True
wStop = False
end sub
'way to stop scan
Private Sub form_clic(sender As Object, e As MouseEventArgs) Handles MyBase.MouseClick
wStop = True
End Sub
*** Update *****
The webview2 control is rather made to display data, and I have no experience on it.
Also I suggest you use a simpler method, based on System.Net.WebClient() and associated with threading.
Here is a start of code that works:
Dim wStop As Boolean
Dim i As Integer = 0
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim BackProcess = New Thread(Sub() Me.scanWeb())
BackProcess.Priority = ThreadPriority.Normal
BackProcess.Start()
end sub
Sub scanWeb()
Do While Not wStop
Dim WC As New System.Net.WebClient()
'change url for your need
Dim url As String = "https://www.google.fr/search?q=" & ListBox1.Items(i)
Dim s As System.IO.Stream = WC.OpenRead(url)
Dim sr As New System.IO.StreamReader(s)
Dim html As String = sr.ReadToEnd()
If html.Contains("Not found") Then 'beginInvoke allows the back task to communicate with UI
Me.BeginInvoke(Sub() DataGridView1.Rows.Add(ListBox1.Items(i), "In vacanza"))
Else
Me.BeginInvoke(Sub() DataGridView1.Rows.Add(ListBox1.Items(i), "Attivo"))
End If
i += 1
If i > ListBox1.Items.Count - 1 Then i = 0
Loop
End Sub
'button event to stop scanning
Private Sub stopScan_Click(sender As Object, e As EventArgs) Handles stopScan.Click
wStop = True
End Sub

Related

VB .Net navigate each link and get a specific url

I'm having trouble using the web browser in VB .NET to navigate a list of URL's inside a multiline textbox, wait for them for load and get a specific URL (should contain a specific word).
What I have until now:
Private Sub Button4_Click(sender As Object, e As EventArgs) Handles Button4.Click
Dim webClient As New System.Net.WebClient
'Dim htmlDoc As New HtmlAgilityPack.HtmlDocument()
For Each strLine As String In TextBox4.Text.Split(vbCrLf)
Console.WriteLine("Turning False")
Console.WriteLine("----")
WebBrowser1.Navigate(strLine)
Console.WriteLine("Waiting for navigation - " & strLine)
Console.WriteLine("Navigated")
Next
For Each link In links
TextBox6.Text = TextBox6.Text & link & vbCrLf
Next
Dim lines As New List(Of String)(TextBox6.Lines)
For i As Integer = lines.Count - 1 To 1 Step -1
If lines(i) = lines(i - 1) Then
lines.RemoveAt(i)
End If
Next
TextBox6.Lines = lines.ToArray
End Sub
Private Sub WebBrowser1_DocumentCompleted(sender As Object, e As WebBrowserDocumentCompletedEventArgs) Handles WebBrowser1.DocumentCompleted
For Each ele As HtmlElement In WebBrowser1.Document.Links
'Get whatever text there is in the 'href' attribute
Dim eletarget As String = ele.GetAttribute("href")
'Add it to the listbox
If eletarget.Contains("cfsecure") Then
links.Add(eletarget)
'Carry on to the next link
End If
Next
End Sub
First of all, it seems it doesn't wait until fully loaded. After that, I don't get any link from what I asked (don't know if it's related to the first problem I have or any mistake in my code getting the href with the word "cfsecure").
Private Sub WebBrowser1_DocumentCompleted(sender As Object, e As WebBrowserDocumentCompletedEventArgs) Handles WebBrowser1.DocumentCompleted
For Each ele As HtmlElement In WebBrowser1.Document.Links
'Get whatever text there is in the 'href' attribute
Dim eletarget As String = ele.GetAttribute("href")
'Add it to the listbox
If eletarget.Contains("cfsecure") Then
links.Add(eletarget)
'Carry on to the next link
End If
Next
End Sub
What I'm missing here?

Making an auto typer from list view

I currently have everything working as it should except for one thing, right now I have the user type into a textbox, press the Add button and it inserts the text into the list view, when the autotyper starts it starts a timer tick with 6000 intervals and types the list but does not go back to the beginning of the list it repeats the last known phrase.
EX:
How can I make it start back over from the beginning if there is nothing left to be typed?
My code for the timer tick
intervalTimer_Tick.Start()
Dim SeprateLine As String
Dim Separator As Integer
If ListedItems.Contains(vbLf) Then
Separator = ListedItems.IndexOf(vbLf)
SeprateLine = ListedItems.Remove(Separator)
ListedItems = ListedItems.Substring(Separator + 1)
Else
SeprateLine = ListedItems
End If
SendKeys.Send(SeprateLine)
SendKeys.Send("{ENTER}")
If ListedItems <> "" Then
End If
End Sub
My code for button
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
For Each LVI As ListViewItem In ListView1.Items
If ListedItems = "" Then
ListedItems = LVI.Text
Else
ListedItems &= vbLf & LVI.Text
End If
Next
intervalTimer_Tick.Start()
End Sub
I think it's great you've started coding in VB.NET. You are almost there, but I want to give you a suggestion. Don't store your values on your user interface - store them in code off the UI thread. Using plain old objects to keep data makes it easier to write and read. Consider a List(Of string) to hold the items, and using a ListBox and DataSource to present the data. This allows for definite separation between what is UI and what is data.
Private ReadOnly items As New List(Of String)()
Private ReadOnly timer As New System.Threading.Timer(AddressOf autoType, Nothing, -1, -1)
Private Sub AddButton_Click(sender As Object, e As EventArgs) Handles AddButton.Click
Dim s = InputBox("Add item", "Add", Nothing)
If s IsNot Nothing Then items.Add(s)
ListBox1.DataSource = Nothing
ListBox1.DataSource = items
End Sub
Private Sub RemoveButton_Click(sender As Object, e As EventArgs) Handles RemoveButton.Click
Dim si = ListBox1.SelectedIndex
If si >= 0 Then
items.RemoveAt(si)
ListBox1.DataSource = Nothing
ListBox1.DataSource = items
End If
End Sub
Private Sub StartButton_Click(sender As Object, e As EventArgs) Handles StartButton.Click
' different buttons / handlers for different intervals
timer.Change(5000, 6000) ' 5s delay before first tick, 6s between subsequent ticks
End Sub
Private Sub autoType(state As Object)
' this ticks off the UI thread, so must Control.Invoke to run on the UI
Me.Invoke(Sub() SendKeys.Send(String.Join(vbLf, items)))
End Sub
To stop it, just change the timer again
timer.Change(-1, -1)

How to show records added to datagridview in real time

A co-worker needs to search our network and her File Explorer search does not work well. I threw this app together quickly to allow her to search and it works well. The results are written to a datagridview, but the results are not shown until the search is complete.
I would like the datagridview to show records as they are added and allow her to cancel the search if she wants.
Using a backgroundworker, I tried to refresh the grid, but as soon as it finds a match, the code stops running. There are no errors, it just stops running.
So how can I get the grid to update as it continues to search?
Public dtResults As DataTable
Dim myDataSet As New DataSet
Dim myDataRow As DataRow
Dim colType As DataColumn
Dim colResult As DataColumn
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
dtResults = New DataTable()
colType = New DataColumn("Type", Type.GetType("System.String"))
colResult = New DataColumn("Search Result", Type.GetType("System.String"))
dtResults.Columns.Add(colType)
dtResults.Columns.Add(colResult)
DataGridView1.DataSource = dtResults
DataGridView1.Columns(1).AutoSizeMode = DataGridViewAutoSizeColumnMode.Fill
End Sub
Private Sub btnSearch_Click(sender As Object, e As EventArgs) Handles btnSearch.Click
btnSearch.Enabled = False
sbStatusBar.Text = "Searching..."
dtResults.Clear()
BackgroundWorker1.RunWorkerAsync()
End Sub
Private Sub BackgroundWorker1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
LoopSubFolders(txtSearchLocation.Text)
End Sub
Public Sub LoopSubFolders(sLocation As String)
Dim di = New DirectoryInfo(sLocation)
Dim mySearchterm As String = LCase(txtSearchTerm.Text)
Dim fiArr As FileInfo() = di.GetFiles()
Dim sSearchTarget As String
sbStatusBar.Text = "Searching " & sLocation
'Search File names in
If cbFileNames.Checked = True Then
For Each myFile In fiArr
sSearchTarget = LCase(myFile.Name)
If sSearchTarget.Contains(mySearchterm) Then
myDataRow = dtResults.NewRow()
myDataRow(dtResults.Columns(0)) = "File"
myDataRow(dtResults.Columns(1)) = Path.Combine(sLocation, myFile.Name)
dtResults.Rows.Add(myDataRow)
End If
Next
End If
For Each d In Directory.GetDirectories(sLocation)
If cbFolderNames.Checked = True Then
sSearchTarget = LCase(d)
If sSearchTarget.Contains(mySearchterm) Then
myDataRow = dtResults.NewRow()
myDataRow(dtResults.Columns(0)) = "Folder"
myDataRow(dtResults.Columns(1)) = d
dtResults.Rows.Add(myDataRow)
End If
End If
LoopSubFolders(d)
Next
End Sub
Private Sub BackgroundWorker1_RunWorkerCompleted(sender As Object, e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
btnSearch.Enabled = True
sbStatusBar.Text = "Complete"
DataGridView1.DataSource = Nothing
DataGridView1.DataSource = dtResults
DataGridView1.Columns(1).AutoSizeMode = DataGridViewAutoSizeColumnMode.Fill
End Sub
Here's an example of how you might do it using the suggested ReportProgress method and ProgressChanged event:
Private table As New DataTable
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'Configure table here.
DataGridView1.DataSource = table
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
'Setup UI here.
'Note that you MUST pass in the TextBox data as you MUST NOT touch the UI directly on the secondary thread.
BackgroundWorker1.RunWorkerAsync({TextBox1.Text, TextBox2.Text})
End Sub
Private Sub BackgroundWorker1_DoWork(sender As Object, e As DoWorkEventArgs) Handles BackgroundWorker1.DoWork
'Get the data passed in and separate it.
Dim arguments = DirectCast(e.Argument, String())
Dim folderPath = arguments(0)
Dim searchTerm = arguments(1)
SearchFileSystem(folderPath, searchTerm)
End Sub
Private Sub SearchFileSystem(folderPath As String, searchTerm As String)
For Each filePath In Directory.GetFiles(folderPath)
If filePath.IndexOf(searchTerm, StringComparison.InvariantCultureIgnoreCase) <> -1 Then
'Update the UI on the UI thread.
BackgroundWorker1.ReportProgress(0, {"File", filePath})
End If
Next
For Each subfolderPath In Directory.GetDirectories(folderPath)
If subfolderPath.IndexOf(searchTerm, StringComparison.InvariantCultureIgnoreCase) <> -1 Then
'Update the UI on the UI thread.
BackgroundWorker1.ReportProgress(0, {"Folder", subfolderPath})
End If
SearchFileSystem(subfolderPath, searchTerm)
Next
End Sub
Private Sub BackgroundWorker1_ProgressChanged(sender As Object, e As ProgressChangedEventArgs) Handles BackgroundWorker1.ProgressChanged
'Get the data passed out and separate it.
Dim data = DirectCast(e.UserState, String())
'Update the UI.
table.Rows.Add(data)
End Sub
Note that you should NEVER touch the UI directly in the DoWork event handler or a method called from it. ONLY touch the UI on the UI thread. That means that the text in your TextBoxes must be extracted BEFORE calling RunWorkerAsync. You can eithewr pass the Strings in as arguments or you can assign them to fields and access them from there on any thread. Don't EVER access a member of a control on other than the UI thread. Some times it will work, sometimes it will appear to work but not do as intended and sometimes it will crash your app. So that you don't have to remember which specific scenarios cause which result, avoid such scenario altogether.
I haven't tested this code so I'm not sure but you may have to call Refresh on the grid or the form after adding the new row to the DataTable.
Variables
Well, let's start from the top with some class level variables:
'Notice the enabled properties.
Private WithEvents BackgroundWorker1 As New BackgroundWorker With {.WorkerReportsProgress = True, .WorkerSupportsCancellation = True}
'To monitor the cancellation, set by the Cancel Button.
Private bgwCancel As Boolean = False
'The DGV source.
Private dtResults As New DataTable
'The start directory.
Private startDir As String
'The search keyword.
Private searchWord As String
'Whether to search the sub directories, from a check box for example.
Private includeSubDirectories As Boolean = True
'Whether to search the files, from another check box.
Private includeFiles As Boolean = True
The Constructor
Prepare your DGV and whatever else you need here.
Sub New()
dtResults.Columns.Add(New DataColumn("Type", Type.GetType("System.String")))
dtResults.Columns.Add(New DataColumn("Search Result", Type.GetType("System.String")))
DataGridView1.DataSource = dtResults
DataGridView1.Columns(1).AutoSizeMode = DataGridViewAutoSizeColumnMode.Fill
'Make sure you add the image column after binding the data source.
Dim imgCol As New DataGridViewImageColumn(False)
With imgCol
.Image = Nothing
.Name = "imgCol"
.HeaderText = ""
.Width = 50
.DefaultCellStyle.NullValue = Nothing
End With
DataGridView1.Columns.Insert(0, imgCol)
End Sub
Iterator
Now, let's write the search routine. I'd do that through an Iterator function:
Private Iterator Function IterateFolders(startDir As String, includeFiles As Boolean, includeSubDir As Boolean) As IEnumerable(Of String)
For Each dirName In IO.Directory.EnumerateDirectories(startDir)
Yield dirName
If includeFiles Then
For Each fileName In IO.Directory.EnumerateFiles(startDir)
Yield fileName
Next
End If
If includeSubDir Then
For Each subDir In IterateFolders(dirName, includeFiles, includeSubDir)
Yield subDir
Next
End If
Next
End Function
The Main Thread Updater
A routine called by the worker's thread to update the DataTable and any control that belongs to the main thread:
Private Sub AddSearchResult(path As String)
If InvokeRequired Then
Invoke(Sub() AddSearchResult(path))
Else
dtResults.Rows.Add(If(IO.File.Exists(path), "File", "Folder"), path)
sbStatusBar.Text = $"Searching {path}"
End If
End Sub
Start
In the click event of the start button, do the necessary validations, assign the values to their variables, and start the back ground worker:
If String.IsNullOrEmpty(txtSearchKeyword.Text) Then Return
If String.IsNullOrEmpty(txtSearchLocation.Text) Then Return
bgwCancel = False
dtResults.Rows.Clear()
startDir = txtSearchLocation.Text
searchWord = txtSearchKeyword.Text.ToLower
includeSubDirectories = chkIncludeSubDirs.Checked
includeFiles = chkFiles.Checked
btnSearch.Enabled = False
sbStatusBar.Text = "Searching..."
BackgroundWorker1.RunWorkerAsync()
Cancel
To cancel the search, in the click event of the cancel button I presume, True the bgwCancel variable:
bgwCancel = True
The BackgroundWorker - DoWork
Private Sub BackgroundWorker1_DoWork(sender As Object, e As DoWorkEventArgs) Handles BackgroundWorker1.DoWork
For Each item As String In IterateFolders(startDir, includeFiles, includeSubDirectories)
If bgwCancel Then
BackgroundWorker1.CancelAsync()
Return
End If
If item.ToLower.Contains(searchWord) Then
AddSearchResult(item)
End If
Threading.Thread.Sleep(100)
Next
End Sub
Note that, Its good practice to give a lengthy routine a BREATH through the Sleep(ms) method of that thread.
The BackgroundWorker - ProgressChanged
I don't think you need it here.
The BackgroundWorker - RunWorkerCompleted
Private Sub BackgroundWorker1_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
If bgwCancel Then
sbStatusBar.Text = "Canceled!"
MessageBox.Show("Canceled by you!")
ElseIf e.Error IsNot Nothing Then
sbStatusBar.Text = "Error!"
MessageBox.Show(e.Error.Message)
Else
sbStatusBar.Text = "Complete"
'YOU DO NOT NEED TO DO THIS. Remove the following
'DataGridView1.DataSource = Nothing
'DataGridView1.DataSource = dtResults
'DataGridView1.Columns(1).AutoSizeMode = DataGridViewAutoSizeColumnMode.Fill
End If
btnSearch.Enabled = True
End Sub
The Image Column
Handle the RowsAdded event of the DGV as follow:
Private Sub DataGridView1_RowsAdded(sender As Object, e As DataGridViewRowsAddedEventArgs) Handles DataGridView1.RowsAdded
If DataGridView1.Columns.Count < 3 Then Return
'if you want to get rid of the default x image.
If e.RowIndex = 0 Then
DataGridView1.Rows(e.RowIndex).Cells("imgCol").Value = Nothing
End If
Dim path As String = DataGridView1.Rows(e.RowIndex).Cells(2).Value?.ToString
If Not String.IsNullOrEmpty(path) Then
If IO.File.Exists(path) Then
DataGridView1.Rows(e.RowIndex).Cells("imgCol").Value = Icon.ExtractAssociatedIcon(path).ToBitmap
Else
DataGridView1.Rows(e.RowIndex).Cells("imgCol").Value = My.Resources.Folder
End If
End If
End Sub
Where the My.Resources.Folder is an icon file of your choice for the folder entries.
Good luck.

if the file not exits then return no error vb

I have start this application every things its work fine but i have a small bug but i can not find the solution to solve the error.
i have debug it and the error its because the file not exist
is there any way to me to populate my datagridview with all *.gif images From a directory and the check if its null or some thing like that.
What i mean is is there any way to my to populate all gif images found on the chose Directory?
in fact i have all ready try like this but i get one error "Provided column already belongs to the DataGridView control.
Well finaly i have found a solution to load all images from a directory to a datagridview programmatic
Here Is The Working Code
Public Class Form5
Private Sub addBtn_Click(sender As Object, e As EventArgs) Handles addBtn.Click
'Populate()
ShowImages()
End Sub
'CLEAR DATAGRIDVIEW
Private Sub clearBtn_Click(sender As Object, e As EventArgs) Handles clearBtn.Click
DataGridView1.Rows.Clear()
End Sub
'WHEN AN IMAGE IS CLICKED
Private Sub DataGridView1_CellContentClick(sender As Object, e As DataGridViewCellEventArgs) Handles DataGridView1.CellContentClick
MessageBox.Show("You Clicked Image At Col: " + e.ColumnIndex.ToString() + " Row: " + e.RowIndex.ToString())
End Sub
Private Sub Form5_Load(sender As Object, e As EventArgs) Handles MyBase.Load
End Sub
Public Sub ShowImages()
Dim directory As New System.IO.DirectoryInfo("C:\avitogifconverter\")
If directory.Exists Then
Dim pngFiles() As System.IO.FileInfo = directory.GetFiles("*.gif")
For Each pngFile As System.IO.FileInfo In pngFiles
If pngFile.Exists Then
Dim image = System.Drawing.Image.FromFile(pngFile.FullName)
Using image
Dim count = 1
' do something with the image like show in picture box
'CONSTRUCT IMG COLUMN
Dim imgCol As DataGridViewImageColumn = New DataGridViewImageColumn()
imgCol.HeaderText = "Photo"
imgCol.Name = "Col 1"
DataGridView1.Columns.Add(imgCol)
'CONSTRUCT ROWS
'FIRST ROW
Dim img As Image = System.Drawing.Image.FromFile(pngFile.FullName)
Dim row As Object() = New Object() {img, img, img}
DataGridView1.Rows.Add(row)
End Using
End If
Next
End If
End Sub
End Class
Using Directory.EnumerateFiles, you could do something like this:
Dim row = New List(Of Image)(3)
For Each filename In Directory.EnumerateFiles("C:\avitogifconverter", "*.gif")
row.Add(Image.FromFile(filename))
If row.Count = 3 Then
DataGridView1.Rows.Add(row.ToArray())
row.Clear()
End If
Next
If row.Count > 0 Then
DataGridView1.Rows.Add(row.ToArray())
row.Clear()
End If

VB Thread Timer Update UI

I made a small program that allows for individual timer countdowns for each button clicked. (e.g. clicking on button 1 will start a countdown for button 1 whilst updating the text on the button itself to reflect the time remaining.)
My worry now is that I'm not sure how well my program would work in the long run. Here's a snippet of the code.
Private Sub depBtn_Clicked(sender As Button, e As EventArgs)
If sender.BackColor = Color.Green Then
Dim depRow() As Data.DataRow
Dim id As String = sender.Name
depRow = DepartmentDataSet.Departments.Select("ID Like '" & id & "'")
sender.BackColor = Color.Red
Dim timerBtn As New DepartmentTimer(sender, depRow(0)("Duration"), depRow(0)("ID"))
Dim TimerDelegate As New System.Threading.TimerCallback(AddressOf TimerTask)
Dim TimerItem As New System.Threading.Timer(TimerDelegate, timerBtn, 0, 1000)
timerBtn.timerRef = TimerItem
End If
End Sub
Private Delegate Sub TimerTaskDelegate(ByVal obj As Object)
Private Sub TimerTask(ByVal obj As Object)
If Me.InvokeRequired() Then
Me.Invoke(New TimerTaskDelegate(AddressOf TimerTask), obj)
Else
Dim depTimer As DepartmentTimer = DirectCast(obj, DepartmentTimer)
depTimer.countDown()
If depTimer.duration = -1 Then
depTimer.finish()
depTimer.timerRef.Dispose()
End If
End If
End Sub
I have read and also experienced that if I were to update on the UI thread directly from the timer callback the whole program would crash. So I ended up using a delegate in accordance to here http://tech.xster.net/tips/invoke-ui-changes-across-threads-on-vb-net/.
Is this a proper way of doing it or am I doing anything redundant/inefficient?
Also when I dispose of the Timer object. How would I go about cleaning up the DepartmentTimer class instance (timerBtn)? The button can be activated again once the timer runs out so I'm afraid that the instances would build up if I don't take care of them properly.
Thanks in advance for any help.
Since you're not actually doing anything with the Timer except immediately Invoking back to the main UI thread, you might as well just use one System.Windows.Forms.Timer and update them all in the same handler.
Something like:
Public Class Form1
Private timers As New List(Of DepartmentTimer)
Private WithEvents Tmr As New System.Windows.Forms.Timer
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
Tmr.Interval = 1000
Tmr.Start()
End Sub
Private Sub depBtn_Clicked(sender As Button, e As EventArgs)
If sender.BackColor = Color.Green Then
Dim depRow() As Data.DataRow
Dim id As String = sender.Name
depRow = DepartmentDataSet.Departments.Select("ID Like '" & id & "'")
sender.BackColor = Color.Red
timers.Add(New DepartmentTimer(sender, depRow(0)("Duration"), depRow(0)("ID")))
End If
End Sub
Private Sub Tmr_Tick(sender As Object, e As EventArgs) Handles Tmr.Tick
For i As Integer = timers.Count - 1 To 0 Step -1
Dim depTimer As DepartmentTimer = timers(i)
depTimer.countDown()
If depTimer.duration = -1 Then
depTimer.finish()
timers.RemoveAt(i)
End If
Next
End Sub
End Class