BeginInvoke - What I thought I knew

[dbasnett]

On my dual core system I thought the UI would get updated sometimes when executing this code:

    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        Dim t As New Threading.Thread(AddressOf foo)
        t.IsBackground = True
        t.Start()
    End Sub

    Private Sub foo()
        For x As Integer = 1 To 50000
            updUI(x)
            'Threading.Thread.Sleep(0)
        Next
    End Sub

    'Dim updUIare As New Threading.AutoResetEvent(True)
    Delegate Sub updUIdel(i As Integer)

    Private Sub updUI(i As Integer)
        If Me.InvokeRequired Then
            'updUIare.WaitOne()
            Dim d As New updUIdel(AddressOf updUI)
            Me.BeginInvoke(d, i)
        Else
            Label1.Text = i.ToString("n0")
            ProgressBar1.Value = i Mod 100
            'updUIare.Set()
        End If
    End Sub

but it does not until the end. I didn't expect it to be pretty. Using the AutoResetEvent works, as would Invoke.

This is a simple reproduction of some code I was testing for a worst case situation.