Solved

Using Delegates for Cross-thread operations

Posted on 2008-10-13
2
496 Views
Last Modified: 2012-06-21
I need some help understanding the use of Delegates. I would like to have a listbox on the main form and be able to add to it from other threads. Below is some example code that I've been playing with but not very successfully. Can someone point out what I'm doing wrong? I keep getting "Cross-thread operation not valid". Thanks!
Public Class One
    Private Delegate Sub Logger(ByVal _message As String)
    Dim t As Threading.Thread
    Dim WithEvents oTwo As New Two
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        t = New Threading.Thread(AddressOf oTwo.startCounting)
        t.Start()
    End Sub
    Private Sub updateList(ByVal entry As String)
        ListBox1.Items.Add(entry)
    End Sub
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        t.Abort()
    End Sub
    Sub ThreadLogging(ByVal entry As String) Handles oTwo.LogUpdated
        Invoke(New Logger(AddressOf updateList), entry)
        Dim writer As Logger
        writer = AddressOf updateList
        writer.Invoke(entry)
    End Sub
End Class
 
Public Class Two
    Public Event LogUpdated(ByVal entry As String)
 
    Public Sub startCounting()
        Dim count As Integer = 0
        While True
            WriteMonitorLog(count.ToString)
            count += 1
            Threading.Thread.Sleep(100)
        End While
    End Sub
    Private Sub WriteMonitorLog(ByVal entry As String)
        RaiseEvent LogUpdated(entry)
    End Sub
End Class

Open in new window

0
Comment
Question by:Tharo_Systems
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
2 Comments
 
LVL 13

Accepted Solution

by:
crazyman earned 500 total points
ID: 22703457
change this

Sub ThreadLogging(ByVal entry As String) Handles oTwo.LogUpdated
        Invoke(New Logger(AddressOf updateList), entry)
            End Sub
0
 

Author Comment

by:Tharo_Systems
ID: 22703501
I knew it had to be something simple! Thanks so much!
0

Featured Post

[Webinar] Learn How Hackers Steal Your Credentials

Do You Know How Hackers Steal Your Credentials? Join us and Skyport Systems to learn how hackers steal your credentials and why Active Directory must be secure to stop them. Thursday, July 13, 2017 10:00 A.M. PDT

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Calculating holidays and working days is a function that is often needed yet it is not one found within the Framework. This article presents one approach to building a working-day calculator for use in .NET.
It was really hard time for me to get the understanding of Delegates in C#. I went through many websites and articles but I found them very clumsy. After going through those sites, I noted down the points in a easy way so here I am sharing that unde…
NetCrunch network monitor is a highly extensive platform for network monitoring and alert generation. In this video you'll see a live demo of NetCrunch with most notable features explained in a walk-through manner. You'll also get to know the philos…
In this video you will find out how to export Office 365 mailboxes using the built in eDiscovery tool. Bear in mind that although this method might be useful in some cases, using PST files as Office 365 backup is troublesome in a long run (more on t…

623 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question