.NET Add Item To ListView Cross Threads

[.NET] Add Item To ListView Cross Threads - Printable Version

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+---- Thread: [.NET] Add Item To ListView Cross Threads (/showthread.php?tid=5181841)

Add Item To ListView Cross Threads - 270z - Feb 23, 2016

So I am scraping sites then collecting data and sending them to a listview. but when I do this with a thread it does not send them to the listview...

No thread: works
with thread: No works

Here is my delegate:

Code 
Private Delegate Sub ListViewAddItem_delegate(ByVal Title As String, ByVal Content As String)

    Private Sub ListViewAddItem(ByVal Title As String, ByVal Content As String)

        If CampaignForm.ListView1.InvokeRequired Then

            Dim d As New ListViewAddItem_delegate(AddressOf ListViewAddItem)

            CampaignForm.ListView1.BeginInvoke(d, {Title, Content})

        Else

            Dim lvi As New ListViewItem(Title)

            lvi.SubItems.Add(Content)

            CampaignForm.ListView1.Items.AddRange(New ListViewItem() {lvi})

            CampaignForm.ListView1.Update()

        End If

    End Sub

Inside the background worker I use this code:

Code 
ListViewAddItem(Title, CountWords(Body))

If someone sees something I am doing wrong please say :)

* - BahNahNah - Feb 23, 2016

Either just ude Invoke or you need a EndInvoke method.
Also, why is this a delegate and why are you using AddRange for one item?

* - Cairns - Feb 24, 2016

Private Delegate Sub ListViewAddItem_delegate(ByVal Title As String, ByVal Content As String)
Private Sub ListViewAddItem(ByVal Title As String, ByVal Content As String)
If InvokeRequired Then
invoke(new ListViewAddItem_delegate(addressof listviewadditem),title,content)
return
end if

Dim lvi As New ListViewItem(Title)
lvi.SubItems.Add(Content)
CampaignForm.ListView1.Items.Add(lvi)
CampaignForm.ListView1.Update()
End Sub

* - 270z - Feb 24, 2016

(Feb 24, 2016 04:30 AM)Cairns Wrote: Private Delegate Sub ListViewAddItem_delegate(ByVal Title As String, ByVal Content As String)
Private Sub ListViewAddItem(ByVal Title As String, ByVal Content As String)
If InvokeRequired Then
invoke(new ListViewAddItem_delegate(addressof listviewadditem),title,content)
return
end if

Dim lvi As New ListViewItem(Title)
lvi.SubItems.Add(Content)
CampaignForm.ListView1.Items.Add(lvi)
CampaignForm.ListView1.Update()
End Sub

Still does not add anything to the listview...

I can't think of a reason why that wouldn't work hmm

* - Niǌa - Feb 24, 2016

You can just do a normal invoke:

Code 
Invoke(Sub()

Dim item As New ListViewItem(Title)

item.SubItems.Add(Content)

CampaignForm.ListView1.Items.Add(item)

End Sub)

* - Cairns - Feb 24, 2016

Then you are doing something completely wrong. You are also referring to another form.

* - drake08 - Feb 24, 2016

I kind of hate vb so I always provide answers in C# since I know this language pretty good.I hope that's not an issue for you.

Code 
delegate void ListViewAddItem(String title, String content);

private void AddLViewItem(String title, String content) {

  if (lstView.InvokeRequired)

    Invoke(new ListViewAddItem(AddLViewItem), title, content);

  else

    lstView.Items.Add(new ListViewItem(new String[] { title, content }));

}

And this is how you can test it:

new Thread(() => { AddLViewItem("item", "subitem"); }).Start();

* - Niǌa - Feb 24, 2016

(Feb 24, 2016 01:40 PM)270z Wrote: Yes I am

You ignored my post. And the code I posted works for me when cross-thread accessing a listview.