How to update listview on a different form using backgroundworker

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Hello,

My backgroundworker reads from a txt file database and should put the data in a listview on the main form. Nothing came up in the listview, and I proved that data was going to it but was not written due to threading errors and such, but I don't know how to make it work.

-Rixterz

Posted 13-Aug-14 23:24pm

Rixterz123

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OriginalGriff · Answer 1 · 2014-08-14T00:15:00

Solution 1

You can't access UI elements except from the thread on which they were created: the UI thread. When you try, you get a cross thread exception - as you have seen.

Fortunately it's simple to fix: just Invoke[^] the control from the background worker, and it will move the execution onto the UI thread for you.

Posted 14-Aug-14 0:15am

OriginalGriff

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[no name] 14-Aug-14 7:16am

Nope. I have this code:

Delegate Sub LoadPlayerListDelegate()
Private Sub ReadFromDatabase()
Dim Usernames As String = Nothing
Try
Dim r As New IO.StreamReader(My.Settings.DatabaseLocation)
Do While r.Peek() <> -1
Usernames &= r.ReadLine().Split(vbTab)(3) & "/"
Loop
r.Close()
If Form1.ListView2.InvokeRequired Then
Dim del As New LoadPlayerListDelegate(AddressOf ReadFromDatabase)
Form1.ListView2.Invoke(del)
Else
Form1.LoadPlayerList(Usernames)
End If
Me.Close()
Catch ex As Exception
If MessageBox.Show("Error: could not read from database." & vbNewLine & "Retry?", "Could not read from database", MessageBoxButtons.YesNo, MessageBoxIcon.Error, MessageBoxDefaultButton.Button1) = Windows.Forms.DialogResult.Yes Then
ReadFromDatabase()
Else
Application.Exit()
End If
End Try
End Sub
________________________
And on Form1, this:
________________________

Public Sub LoadPlayerList(Usernames As String)
MsgBox("Loadplayerlist here. usernames=" & Usernames) 'to make sure the sub is run
Me.Text = "huh" '<--- NOT WORKING - CROSSTHREADING ISSUES :C
For i As Integer = 0 To Usernames.Split("/").Count - 1
ListView2.Items.Add(Usernames.Split("/")(i))
Dim StatusBox = ListView2.Items(ListView2.Items.Count - 1).SubItems(0)
StatusBox.ForeColor = Color.Cyan
StatusBox.Text = "PINGING..."
Next
End Sub