thread problem

"Bernie Yaeger" <be*****@cherwe llinc.com> schrieb

Here's the real problem: I am trying to call a method/sub that has
arguments. I begin to understand that a thread is its own world, has
its own heap, doesn't even recognize global variables from another
thread, etc.
A thread is just a sequence of executed statements. Apart from the stack
containig local variables, data is not thread specific.

Is there a way to use invoke to overcome this? If I can
use invoke to launch a performclick - which has arguments - then I
should be able to use it to do what I want. Can you give me a simple
example of using invoke?

You probably know that windows applications are message driven. The OS

sends the messages, like mouse movements and pressed keys, to a window by putting the messages in a message queue. Any thread that created a window is a UI
thread and has a message queue. A thread gets the messages only for those
windows that have been created in the same thread. The thread must process
the messages and send them to the window they belong to. This message loop
is contained in the method Application.Run , also in Form.ShowDialog . Usually an application has only one UI thread. Application.Run is usually called in Sub Main.

Now, a basic rule is that only the thread creating a window can access it.
The Invoke method (or BeginInvoke) can be compared to sending a message to
the window in the other thread. Using the Framework you can do a little bit more: You can specify a procedure that is to be called in the other thread. You can also pass arguments to the procedure.

If there's a reference to the button available in your second thread, you
can call the button's Invoke method and specify the method to be called:

Button1.Invoke( New MethodInvoker(A ddressOf Button1.Perform Click))

--
Armin

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

* "Bernie Yaeger" <be*****@cherwe llinc.com> scripsit:

Here's the real problem: I am trying to call a method/sub that has
arguments. I begin to understand that a thread is its own world, has its own heap, doesn't even recognize global variables from another thread, etc. Is there a way to use invoke to overcome this? If I can use invoke to
launch a performclick - which has arguments - then I should be able to use it to do what I want. Can you give me a simple example of using invoke?

Quick and Dirty:

\\\
Imports System.Threadin g

.
.
.

Private m_str As String

Private Sub Form1_Load( _
ByVal sender As System.Object, _
ByVal e As System.EventArg s _
) Handles MyBase.Load
Dim t As Thread = New Thread(AddressO f Me.AddThread)
t.Start()
End Sub

Private Sub AddThread()
If Me.ListBox1.Inv okeRequired Then
Dim i As Integer
SyncLock ListBox1.GetTyp e()
For i = 1 To 1000
m_str = "Item " & i.ToString()
Me.ListBox1.Inv oke(CType(Addre ssOf Me.Add,
MethodInvoker))
Next i
End SyncLock
End If
End Sub

Private Sub Add()
Me.ListBox1.Ite ms.Add(m_str)
End Sub
///

--
Herfried K. Wagner [MVP]
<http://www.mvps.org/dotnet>