CODEWITHSUNDEEP
c#multithreadinglistbox
Jones
Jones

Reputation: 578

Updating from different thread didn't update Listbox

I'm learning C# and just started to practice with thread concept. I can't update the Listbox to show the data actually from a different thread other than Main thread.

private void DoThreadBtn_Click(object sender, EventArgs e)
{
    ListBoxS.DataSource = sl.dump();  //This update the ListBox.
    //t = new Thread(dumpList);    //This don't update the Listbox
    //t.Start();
}
TestForm.ListBoxTest.StringList sl = new ListBoxTest.StringList();
public void dumpList()
{
    ListBoxS.DataSource = sl.dump(); //Returns a List<string>()
}

Which is wrong here? And to fix it, which part I should learn? Thread or Delegate or Lamda?

Upvotes: 0

Views: 886

Answers (2)

user3820843
user3820843

Reputation:

In VB I like to do it this way (the concept should carry over to C# almost identically)

Here is how I like to update my UI from another thread. Imagine that "Sub Method" updates the UI and DoMethod is called from another thread. Note that in my case I was updating a listbox that was bound to an observable collection using a data template. In my code I have to call listbox.items.refresh to have the screen reflect my changes. I am really new to WPF and VB (Grumpy old C++ Win32/MFC guy) so this is probably the most horrible code ever.

NOTE - the ellipses (...) is the variable parameter list. I like to match it to my original subs parameter list.

Delegate Sub DelegateMethod(...)
Sub Method(...)

End Sub

Public Sub DoMethod(...)

    Dim DM As DelegateMethod = AddressOf Method
    Me.Dispatcher.Invoke(DM, ...)

End Sub

Upvotes: 0

misak
misak

Reputation: 342

In WinForms application cal:

public void dumpList()
{
    if (this.InvokeRequired)
    {
       this.Invoke(new MethodInvoker(this.dumpList));
       return;
    }

    ListBoxS.DataSource = sl.dump(); //Returns a List<string>()
}

If the control's Handle was created on a different thread than the calling thread, property InvokeRequired = true (othervise false)

Upvotes: 1

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