adding asynchronous support

[matt]

i have a VB.net application that connects to the internet to download an xml
file and parse it. It works correctly, but "locks up" until that function
returns. i want to add asynchronous support, but i'm confused on where i
add the code. If i want just this function to be in another thread, what do
i add to it? Also, what do i add to call the function? thanks,

 

[Paul Bunting]

Something like...

IMPORTS System.Threading

Private Sub frmMe_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
Dim objThread As New Thread(AddressOf fnThreadToRun)
objThread.IsBackground = True
objThread.Priority = ThreadPriority.Lowest
objThread.Name = "MyThread"
objThread.Start()
end sub

Private Sub fnThreadToRun()
'.... do something
End Sub

Regards,

P

 

[Cor Ligthert [MVP]]

Matt,

If you use version 2005 have than a look at backgroundworker

http://msdn2.microsoft.com/en-us/library/c8dcext2.aspx

The demonstrations are there

Cor

 

[matt]

hey this is great. It was exactly what i needed. I played around w/ adding
a second thread to my program. I learned that is has to be a subroutine and
that you can't "pass parameters" you have to pull them from the thread,
which is fine, and i made a flag so i can check when its done, however, i'm
having trouble getting the parameters it saved. i have variables and a sub
in a class. I have an object in my program for hte class, and then another
object that is the subroutine from the class. the subroutine stores
variables within that class. i used to pull the variables, they were not
returns, however, now i can't get to these. here is the basic psuedo code

class1:
var1
var2
sub1()
do something with var1
store in var2

myobject = class1
thread = myobject.sub1

myobject.var1 = something
thread.start()
do something with myobject.var2

well, var1 and var2 are empty outside of the thread, but populated inside
the thread. i used this same approach w/o the thread, and i was able to see
my varibles. Is there some reason my thread isn't storing variables like
the sub did without the thread?

thanks for your help!

 

[matt]

disregard that! i complete forgot that it was in another thread. it was
trying to use the parameters before it was done processing them. it works
perfectly! thanks

 

[matt]

Hey thanks again for getting me started on threads. I have another
question. I initiated the thread at the top of my code, and changed the
settings in the "load" sub. Later in my program, i started the thread, and
it ran fine. Where i'm having trouble is when it stops and i want to run it
again. How should i rerun the thread? When my code detects that the thread
has completed, i tried to use thread.abort, but when i do thread.start
again, i get an error saying the thread has stopped and can't be restarted.
How do i restart it? Do I reinitiate the thread each time? I tried that by
initiating the thread once at the begining, and again each time i want it to
run again. There is one problem, when i look at my program in Task Manager,
each time it runs the thread, it adds a new thread. Do i have to kill the
thread each time? Anyway, did i miss the concept of how this works?

Thanks!