Hi everybody, I'm populating a listbox from an async download string using httpclient.
The listbox is slightly modified as I needed a scroll event and i found online a really cool class for it.
So I'm using the same code as here: https://stackoverflow.com/questions/...01853#64001853
And the helper class:
So instead of using a button to stop the timer, I am using the listbox scroll event:
but this seems not working as i get the following error:
System.ObjectDisposedException: 'CancellationTokenSource has been cancelled.
The same error also when I'm using the same code in listbox mouse enter event..
I wanted to stop the timer when the mouse enter the listbox and start again when the mouse leave it.
Does anyone have any idea about how to solve it?
In the simple buttons is working perfectly.
Thanks
The listbox is slightly modified as I needed a scroll event and i found online a really cool class for it.
So I'm using the same code as here: https://stackoverflow.com/questions/...01853#64001853
Code:
Private downloader As MyDownloader = Nothing
Private Sub btnStartDownload_Click(sender As Object, e As EventArgs) Handles btnStartDownload.Click
Dim progress = New Progress(Of String)(
Sub(data)
' We're on the UI Thread here
ListBox1.Items.Clear()
ListBox1.Items.AddRange(Split(data, vbLf))
RichTextBox1.SelectionStart = RichTextBox1.TextLength
End Sub)
Dim url As Uri = New Uri("https://SomeAddress.com")
downloader = New MyDownloader()
' Download from url every 1 second and report back to the progress delegate
downloader.StartDownload(progress, url, 1)Code:
Imports System.Diagnostics
Imports System.Net
Imports System.Net.Http
Imports System.Text.RegularExpressions
Public Class MyDownloader
Private Shared ReadOnly client As New HttpClient()
Private ReadOnly cts As CancellationTokenSource = New CancellationTokenSource()
Private interval As Integer = 0
Public Sub StartDownload(progress As IProgress(Of String), url As Uri, intervalSeconds As Integer)
interval = intervalSeconds * 1000
Task.Run(Function() DownloadAsync(progress, url, cts.Token))
End Sub
Private Async Function DownloadAsync(progress As IProgress(Of String), url As Uri, token As CancellationToken) As Task
Dim responseData As String = String.Empty
Dim pattern As String = "<(?:[^>=]|='[^']*'|=""[^""]*""|=[^'""][^\s>]*)*>"
Dim downloadTimeWatch As Stopwatch = New Stopwatch()
downloadTimeWatch.Start()
Do
If cts.IsCancellationRequested Then Return
Try
Using response = Await client.GetAsync(url, HttpCompletionOption.ResponseContentRead, token)
responseData = Await response.Content.ReadAsStringAsync()
responseData = WebUtility.HtmlDecode(Regex.Replace(responseData, pattern, ""))
End Using
progress.Report(responseData)
Dim delay = interval - CInt(downloadTimeWatch.ElapsedMilliseconds)
Await Task.Delay(If(delay <= 0, 10, delay), token)
downloadTimeWatch.Restart()
Catch tcEx As TaskCanceledException
' Don't care - catch a cancellation request
Debug.Print(tcEx.Message)
Catch wEx As WebException
' Internet connection failed? Internal server error? See what to do
Debug.Print(wEx.Message)
End Try
Loop
End Function
Public Async Function StopDownload() As Task
Try
cts.Cancel()
client?.CancelPendingRequests()
Await Task.Delay(interval)
Finally
client?.Dispose()
cts?.Dispose()
End Try
End Function
End ClassCode:
Await downloader.StopDownload()System.ObjectDisposedException: 'CancellationTokenSource has been cancelled.
The same error also when I'm using the same code in listbox mouse enter event..
I wanted to stop the timer when the mouse enter the listbox and start again when the mouse leave it.
Does anyone have any idea about how to solve it?
In the simple buttons is working perfectly.
Thanks