Visual Basic, Child Thread Blocking Main Thread

Question

I\'ve run into a little issue with a simple file copying application I\'m writing in Visual Basic 2005. I have a main thread which looks after the GUI, and for the file scanning

Answer 1

From what i can tell all calls to the System are also GUI Thread based no matter if you want them or not. And Control.CheckForIllegalCrossThreadCalls = False is very bad, you always want to write your thread and ( if beginner ) run code and everytime it breaks out to code to write a delegate and an invoke function for that part of your thread ( taking up the most minimal time ) one can in the Gui(Main) thread.

Here is an example with full sourcecode

http://www.codeproject.com/Articles/15104/Multithreading-with-VB-NET-A-beginner-s-choice

in your thread

Control.CheckForIllegalCrossThreadCalls = False -- this needs removed If check_scanfirst.Checked Then -- this needs a delegate and invoke method status1.Text = "Scanning..." -- this needs a delegate and invoke method bytestocopy = 0 scandir(src) -- if scandir(has calls to gui )this needs a delegate and invoke method but inside of Scandir()

    filesscanned = True
    MsgBox("Scanning completed")              -- this needs a delegate and invoke method ( keep in mind thread will keep running even if mesgbox not clicked )
End If

If check_delete.Checked Then              -- this needs a delegate and invoke method
    ' Do a clean of the destination, removing any files that don't exist in the source dir
End If

If filesscanned Then
    ProgressBar1.Visible = True             -- this needs a delegate and invoke method
    ProgressBar1.Minimum = 0             -- this needs a delegate and invoke method
    ProgressBar1.Maximum = 100             -- this needs a delegate and invoke method
    ProgressBar1.Refresh()             -- this needs a delegate and invoke method
End If

checkdir(src)
MsgBox("Copying completed")             -- this needs a delegate and invoke method
If filesfailed > 0 Then
    MsgBox("Warning: " + Str(filesfailed) + " files were not copied successfully.")             -- this needs a delegate and invoke method
End If
guistop()             -- this needs a delegate and invoke method if (guistop makes calls to gui )

so if you can't tell your making lots of calls to the gui... heres how i would write it to make it really simple

how i would write your code ( wrote this in word some code may need a tweak )

Private sub DoStuffBeforeCopy()
If check_scanfirst.Checked Then
    status1.Text = "Scanning..."
    bytestocopy = 0
trd_copy.ParameterizedStart(src) //start thread
end sub

CopyTask(byval src as *string*?)
    scandir(src) – put the code here or make another thread ( src is better )
    filesscanned = True

    invoke-MsgBox("Scanning completed")

    invoke If check_delete.Checked Then

    If filesscanned Then
        Invoke-ProgressBar1.Visible = True
        Invoke-ProgressBar1.Minimum = 0
        Invoke-ProgressBar1.Maximum = 100
        Invoke-ProgressBar1.Refresh()
    End If

    checkdir(src) – put the code here or make another thread ( src is better )

    invoke-MsgBox("Copying completed")

    If filesfailed > 0 Then
        Invoke-MsgBox("Warning: " + Str(filesfailed) + " files were not copied successfully.")
    End If

    guistop()– put the code here or make another thread ( src is better )

End sub

** DO THIS FOR ANY Delegat / invoke needed

for threads calls with parameters

trd_copy.ParameterizedStart(src)

Delegate Sub nameofDelegate(s As Integer)
Sub nameofDelegate+NameofSub(ByVal s As Integer)
    If Form1.ProgressBar1.InvokeRequired Then
        Dim d As New nameofDelegate (AddressOf nameofDelegate+NameofSub)
        NameOfYourForm.Invoke(d, New Object() {s})
    Else
        If s = 1 Then
            NameOfYourForm.ProgressBar1.Refresh() ** Or other Gui Functions
        Else

        End If
    End If
End Sub

For Thread calls without parametrs

trd_copy.Start()

Delegate Sub nameofDelegate()
Sub nameofDelegate+NameofSub()
    If Form1.ProgressBar1.InvokeRequired Then
        Dim d As New nameofDelegate (AddressOf nameofDelegate+NameofSub)
        NameOfYourForm.Invoke(d, New Object())
    Else
       NameOfYourForm.ProgressBar1.Refresh() ** Or other Gui Functions
    End If
End Sub