Simple thead question .... what am I doing wrong?

[M O J O]

Hi,

I have a little test project. I spin up a thread, lets it sleep for a
second and then the thread makes a button visible ... or at least should
make it visible, which it doesn't do.

---------------------------------------------------------------------------

Here's my thread class:

Imports System.Threadin g

Public Class MyThreadClass

Private _thread As Thread
Public Delegate Sub ThreadDone(ByVa l IsOnline As Boolean)
Public OnThreadDone As ThreadDone
Public Sub Run()
_thread = New Thread(AddressO f Start)
_thread.IsBackg round = True
_thread.Start()
End Sub
Public Sub SpinDown()
If _thread Is Nothing Then Exit Sub
_thread.Abort()
_thread = Nothing
End Sub
Public Sub Abort()
If _thread Is Nothing Then Exit Sub
_thread.Abort()
_thread = Nothing
End Sub
Private Sub Start()
Try
_thread.Sleep(1 000)
OnThreadDone.In voke(True)
Catch
OnThreadDone.In voke(False)
Finally
End Try
End Sub

End Class

---------------------------------------------------------------------------

And here's my form code:

Private _thread As MyThreadClass

Private Sub Form1_Load(ByVa l sender As System.Object, ByVal e As _
System.EventArg s) Handles MyBase.Load
_thread = New MyThreadClass
_thread.OnThrea dDone = AddressOf OnThreadDone
_thread.Run()
End Sub
Public Sub OnThreadDone(By Val status As Boolean)
Me.Button1.Visi ble = True
' The button is still hidden :o(((
End Sub

---------------------------------------------------------------------------

What am I doing wrong??

Why doesn't the button show up?

Thanks in advance!!

M O J O

[Peter Huang]

Hi,

When you call a delegate synchronously, the Invoke method calls the target
method directly on the current thread.
For more details, take a look at the link below.
Asynchronous Delegates
http://msdn.microsoft.com/library/de...us/cpguide/htm
l/cpovrasynchrono usdelegates.asp

You may the code below,
Private _thread As MyThreadClass
Public Sub OnThreadDone(By Val status As Boolean)
Me.Button1.Visi ble = True
' The button will be visible now :)))
End Sub
Private Sub Form1_Load(ByVa l sender As System.Object, ByVal e As
System.EventArg s) Handles MyBase.Load
_thread = New MyThreadClass
_thread.fm = Me
_thread.OnThrea dDone = AddressOf OnThreadDone
_thread.Run()
End Sub

Public Class MyThreadClass
Public fm As Form1
''''Pass in the Form1's reference
Private _thread As Thread
Public Delegate Sub ThreadDone(ByVa l IsOnline As Boolean)
Public OnThreadDone As ThreadDone
Public Sub Run()
_thread = New Thread(AddressO f Start)
_thread.IsBackg round = True
_thread.Start()
End Sub
Public Sub SpinDown()
If _thread Is Nothing Then Exit Sub
_thread.Abort()
_thread = Nothing
End Sub
Public Sub Abort()
If _thread Is Nothing Then Exit Sub
_thread.Abort()
_thread = Nothing
End Sub
Private Sub Start()
Try
_thread.Sleep(1 000)
'Call the form1's invoke, so that the delegate method OnThreadDone will
call on
'Form1's thread
fm.Invoke(OnThr eadDone, New Object() {True})
Catch
fm.Invoke(OnThr eadDone, New Object() {False})
Finally
End Try
End Sub
End Class

Regards,
Peter Huang
Microsoft Online Partner Support
Get Secure! www.microsoft.com/security
This posting is provided "as is" with no warranties and confers no rights.

[Armin Zingler]

"M O J O" <mojo@_no_spam_ delete_this_new websolutions.dk > schrieb

Hi,

I have a little test project. I spin up a thread, lets it sleep for a
second and then the thread makes a button visible ... or at least
should
make it visible, which it doesn't do.

-------------------------------------------------------------------------- -
Here's my thread class:

Imports System.Threadin g

Public Class MyThreadClass

Private _thread As Thread
Public Delegate Sub ThreadDone(ByVa l IsOnline As Boolean)
Public OnThreadDone As ThreadDone
Public Sub Run()
_thread = New Thread(AddressO f Start)
_thread.IsBackg round = True
_thread.Start()
End Sub
Public Sub SpinDown()
If _thread Is Nothing Then Exit Sub
_thread.Abort()
_thread = Nothing
End Sub
Public Sub Abort()
If _thread Is Nothing Then Exit Sub
_thread.Abort()
_thread = Nothing
End Sub
Private Sub Start()
Try
_thread.Sleep(1 000)
OnThreadDone.In voke(True)
Catch
OnThreadDone.In voke(False)
Finally
End Try
End Sub

End Class

-------------------------------------------------------------------------- -
And here's my form code:

Private _thread As MyThreadClass

Private Sub Form1_Load(ByVa l sender As System.Object, ByVal e As
_
System.EventArg s) Handles MyBase.Load
_thread = New MyThreadClass
_thread.OnThrea dDone = AddressOf OnThreadDone
_thread.Run()
End Sub
Public Sub OnThreadDone(By Val status As Boolean)
Me.Button1.Visi ble = True
' The button is still hidden :o(((
End Sub

-------------------------------------------------------------------------- -
What am I doing wrong??

Why doesn't the button show up?

Only the thread creating a window/button can access it. In the Form, in
OnThreadDone, Uue Me.Invoke or Me.Button1.Invo ke to marshal the call to the
thread creating the form/button.
--
Armin

http://www.plig.net/nnq/nquote.html
http://www.netmeister.org/news/learn2quote.html

[Russell Jones]

You've fallen into a classic threading trap--the thread you're using to make
the button visible is not the UI thread.

Here's one way to fix the problem. Add this code to the form.
Private Delegate Sub showButtonDeleg ate()

Public Sub OnThreadDone(By Val status As Boolean)
Dim sb As New showButtonDeleg ate(AddressOf Me.MakeButton1V isible)
If Me.InvokeRequir ed Then
Me.Invoke(sb)
Else
Me.Button1.Visi ble = True
End If
' button is now visible
End Sub

Private Sub MakeButton1Visi ble()
Me.Button1.Visi ble = True
End Sub

Obviously, you could make the code a little more generic than shown here.
The Invoke method is the key to getting UI actions back on the right thread.
You could just as easily check the InvokeRequired property of the button
object itself and use Invoke or not, as required.
"M O J O" <mojo@_no_spam_ delete_this_new websolutions.dk > wrote in message
news:eO******** ******@TK2MSFTN GP11.phx.gbl...

Hi,

I have a little test project. I spin up a thread, lets it sleep for a
second and then the thread makes a button visible ... or at least should
make it visible, which it doesn't do.

-------------------------------------------------------------------------- -
Here's my thread class:

Imports System.Threadin g

Public Class MyThreadClass

Private _thread As Thread
Public Delegate Sub ThreadDone(ByVa l IsOnline As Boolean)
Public OnThreadDone As ThreadDone
Public Sub Run()
_thread = New Thread(AddressO f Start)
_thread.IsBackg round = True
_thread.Start()
End Sub
Public Sub SpinDown()
If _thread Is Nothing Then Exit Sub
_thread.Abort()
_thread = Nothing
End Sub
Public Sub Abort()
If _thread Is Nothing Then Exit Sub
_thread.Abort()
_thread = Nothing
End Sub
Private Sub Start()
Try
_thread.Sleep(1 000)
OnThreadDone.In voke(True)
Catch
OnThreadDone.In voke(False)
Finally
End Try
End Sub

End Class

-------------------------------------------------------------------------- -
And here's my form code:

Private _thread As MyThreadClass

Private Sub Form1_Load(ByVa l sender As System.Object, ByVal e As _
System.EventArg s) Handles MyBase.Load
_thread = New MyThreadClass
_thread.OnThrea dDone = AddressOf OnThreadDone
_thread.Run()
End Sub
Public Sub OnThreadDone(By Val status As Boolean)
Me.Button1.Visi ble = True
' The button is still hidden :o(((
End Sub

-------------------------------------------------------------------------- -
What am I doing wrong??

Why doesn't the button show up?

Thanks in advance!!

M O J O