autoscroll to bottom of multiline textbox being updated by backgroundworker
Try it this way:
'textbox.Text = text
textbox.AppendText(text)
The code you commented out wasn't running on the GUI thread, and as M Granja pointed out, AppendText will automatically scroll to the appended text in the box, so no need to call ScrollToCaret.
almg
Updated on April 06, 2020Comments
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almg about 4 years
I have a background worker control that is set to perform a task, and update a multiline text box on my main UI using a delegate procedure. this is all working perfectly, however once the updating scrolls off the bottom of the text box, the scroll bars appear, but the continuous refreshing causes the text box to stay locked at the top. Ideally, I would like the text box to auto-scroll itself to the bottom to show the latest entry in real-time. What would be the best way to implement this?
I have tried using the
scrolltocaret()
method, with and without aSelectionStart = txtlog.Text.Length
command preceding it. perhaps I'm putting it in the wrong place?some code samples below:
Delegate code:
Delegate Sub updateresults_delegate(ByVal textbox As TextBox, ByVal text As String) Private Sub updatelog_threadsafe(ByVal textbox As TextBox, ByVal text As String) If textbox.InvokeRequired Then Dim mydelegate As New updateresults_delegate(AddressOf updatelog_threadsafe) Me.Invoke(mydelegate, New Object() {textbox, text}) 'Me.txtlog.SelectionStart = txtlog.Text.Length 'Me.txtlog.ScrollToCaret() Else textbox.Text = text End If End Sub
main backgroundworker activity:
For i As Integer = val1 To val2 'generate an IP address from split host parts and current value of i host = s1(0) & "." & s1(1) & "." & s1(2) & "." & i Try 'attempt to ping the IP Dim reply As PingReply = pingsender.Send(host, timeoutval, buffer, options) If reply.Status = IPStatus.Success Then name = System.Net.Dns.GetHostEntry(host)'get DNS entry resulttext += String.Format("{1} - {2}: reply: Bytes={3} time{4} TTL={5}{0}", vbCrLf, name.HostName, reply.Address.ToString, reply.Buffer.Length, getms(reply.RoundtripTime), reply.Options.Ttl) 'print out success text Else resulttext += String.Format(" {1}: Ping failed. {2}{0}", vbCrLf, host, reply.Status.ToString) 'print out fail text End If updatelog_threadsafe(txtlog, resulttext) 'send text to textbox System.Threading.Thread.Sleep(1000) Catch ex As Exception End Try Next
I guess my main question is: I'm pretty certain that the
textbox.scrolltocaret()
is the correct method to use for what I want, but where is the best place for me to put it? I've tried it in the delegate, the main backgroundworker, as well as before & after therunworkerasync()
method. none of these worked, and now I'm stumped!