Hello... I'm working on an application that contains a "BackgroundWorker", the "BackgroundWorker" worked fine but after I started to change some stuff it gives me an error ("Exception has been thrown by the target of an invocation.")... I used a breakpoint to see where it happens, the exception gets thrown at the "End Sub" line of the BackgroundWorker... I then deleted all the code inside of it and ran it again... I still get the error.
-Thanks
You get an error running this code?
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
BackgroundWorker1.RunWorkerAsync()
End Sub
Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
End SubYou get an error running this code?
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click BackgroundWorker1.RunWorkerAsync() End Sub Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork End Sub
Yeah... It an exception thou...
Stumps Me? Must be more to it behind the scenes.
Maybe post some code. The above code should not throw an exception. I would say add a Try Catch Block in the code to see whats wrong. But theres no code!!!
Stumps Me? Must be more to it behind the scenes.
Maybe post some code. The above code should not throw an exception. I would say add a Try Catch Block in the code to see whats wrong. But theres no code!!!
The application gets all the emails and relative links from a webpage, here's ALL the code:
Imports System.Text.RegularExpressions
Imports System.IO
Imports System.Text
Imports System.Net
Public Class Form1
Inherits System.Windows.Forms.Form
Dim EList As String
Dim numE As Integer = 0
Dim LinkList As String
Dim url As String
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Start.Click
If URLs.Text.StartsWith("http://www.") Then
url = URLs.Text
BackgroundWorker1.RunWorkerAsync()
Else
MsgBox("Ivalid URL!")
End If
End Sub
Private Function ExtractEmailAddressesFromString(ByVal source As String) As String()
Dim mc As MatchCollection
Dim i As Integer
mc = Regex.Matches(source, "([a-zA-Z0-9_\-\.]+)@([a-zA-Z0-9_\-\.]+)\.([a-zA-Z]{2,5})")
Dim results(mc.Count - 1) As String
For i = 0 To results.Length - 1
results(i) = mc(i).Value
Next
Return results
End Function
Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
'BackgroundWorker1.ReportProgress(1)
'Dim request As System.Net.HttpWebRequest = System.Net.HttpWebRequest.Create(url)
'BackgroundWorker1.ReportProgress(10)
'Dim response As System.Net.HttpWebResponse = request.GetResponse
'BackgroundWorker1.ReportProgress(20)
'Dim sr As System.IO.StreamReader = New System.IO.StreamReader(response.GetResponseStream())
'BackgroundWorker1.ReportProgress(30)
'Dim rssourcecode As String = sr.ReadToEnd
'BackgroundWorker1.ReportProgress(70)
'Dim emails As String()
'Dim email As String
'Dim results As New StringBuilder
'emails = ExtractEmailAddressesFromString(rssourcecode)
'BackgroundWorker1.ReportProgress(90)
'For Each email In emails
'EList = EList & email & " "
'Next
'BackgroundWorker1.ReportProgress(100)
'///
'Dim Links As String()
'Dim Link As String
'Dim LinkResults As New StringBuilder
'Links = ExtractLinksFromString(rssourcecode)
'BackgroundWorker1.ReportProgress(90)
'For Each Link In Links
'LinkList = LinkList & Link & " "
'BackgroundWorker1.ReportProgress(100)
'Next
End Sub
Private Sub BackgroundWorker1_ProgressChanged(ByVal sender As Object, ByVal e As System.ComponentModel.ProgressChangedEventArgs) Handles BackgroundWorker1.ProgressChanged
ProgressBar.Value = e.ProgressPercentage
Dim iteg As Integer = ProgressBar.Value
Select Case iteg
Case 1
LOG.Text = LOG.Text + vbNewLine + "Getting HTML code..."
Case 30
LOG.Text = LOG.Text + vbNewLine + "Got HTML code."
LOG.Text = LOG.Text + vbNewLine + "Reading HTML code..."
Case 70
LOG.Text = LOG.Text + vbNewLine + "Done reading."
LOG.Text = LOG.Text + vbNewLine + "Finding emails..."
Case 90
LOG.Text = LOG.Text + vbNewLine + "Found emails." + vbNewLine + "Processing emails"
End Select
End Sub
Private Sub BackgroundWorker1_RunWorkerCompleted(ByVal sender As Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
EList = EList.Substring(0, EList.Length - 1)
Dim ESplitList As String() = EList.Split(New Char() {" "c})
Dim email As String
For Each email In ESplitList
If Not EmailList.Items.Contains(email) = True Then
numE += 1
EmailList.Items.Add(email)
End If
Next
LOG.Text = LOG.Text + vbNewLine + "Done!" + vbNewLine + numE.ToString + " new emails added to the list."
numE = 0
EList = ""
End Sub
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
End Sub
Private Sub LOG_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles LOG.TextChanged
LOG.SelectionStart = LOG.Text.Length
LOG.ScrollToCaret()
End Sub
Private Sub Save_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Save.Click
SaveForm.Show()
End Sub
Private Function ExtractLinksFromString(ByVal source As String) As String()
Dim mc As MatchCollection
Dim i As Integer
mc = Regex.Matches(source, "href=(['""])(?!.+://)(?<url>.+?)\1")
Dim results(mc.Count - 1) As String
For i = 0 To results.Length - 1
results(i) = mc(i).Value
Next
Return results
End Function
End ClassLike i said at first: I put "'"s before all the code in the BackgroundWorker's code.
I figured there was more behind the scenes.
Your problem is in the run worker complete part. I don't know what it is. I will look at it later. Add a try catch block in your runworkercomplete sub and put a break point on the catch part or message box the exception. You will probably figure it out. If not post back.
I did a quick look and I will be willing to wager $0.50 that your elist variable is an empty string and your trying to get a sub string from it.
Let me know if any of this information is not correct.
The problem lays in your BackgroundWorker1_ProgressChanged procedure.
You can NOT access controls (which were created in the main thread) from any other thread without using delegates.
Check out this thread => http://www.daniweb.com/software-development/vbnet/threads/400426
Same problem + solution.
Everything about the above post is wrong. The ProgressChanged event is not even being raised because there is no code in the DoWork event that sets a change. And even if the ProgressChanged was raised you CAN access controls in it.
I've already provided the solutions to the problem.
I did a quick look and I will be willing to wager $0.50 that your elist variable is an empty string and your trying to get a sub string from it.
Let me know if any of this information is not correct.
I deleted the first line of code in BackgroundWorker1_RunWorkerCompleted... nothing changed...
I deleted the first line of code in BackgroundWorker1_RunWorkerCompleted... nothing changed.
You don't fix code by deleting other lines of code.
If the string is null then your going to get an exception on the second line.
Too many other factors in this to even do anything. Wheres EmailList? Its not in your form1 class. Is it in some module or other class?
You may need to just start over.
EmailList may not even have a reference.
Everything about the above post is wrong. The ProgressChanged event is not even being raised because there is no code in the DoWork event that sets a change. And even if the ProgressChanged was raised you CAN access controls in it.
When I say there is no code in the DoWork event that sets a change. I mean its all commented out. Well aware there is commented out code that would set a progress change.
@AndyPants
You should start validating things before using them or you will be dealing with things like this from here on.
Before substring a string. If not String.IsNullOrEmpty(aString) andalso aString.Length > 0 then
Before using a list or what ever EmailList is. If EmailList IsNot Nothing Then.
Before setting the minimum or maximum of a progress bar. If value >= progressbar.minimum AndAlso value <= progressbar.maximum then.
And you should put a Try Catch Block in the entire RunWorkerComplete and set a break point on the Catch part so you can read what the exception is.
Good Luck and Happy Trails.
I deleted the first line of code in BackgroundWorker1_RunWorkerCompleted... nothing changed.
Unbelievable. I'll try that next time I get an error. Just delete a line. Great strategy. I think its great. Damn it its not working. I'll just delete this line and see what happens. When all else fails, just delete a line of code.
@GeekByCoiCe Your post is as worthless as this thread.
Thank you very much good sir!
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