Question

I’m using VB 2010 Express.
I have a loop that calls a function named “singlePing” which pings an IP Address.
If the application succeeded to reach that IP it turns a certain label back-color into green,
otherwise – red. (There’s a label for each ip address)

When I’m running my application it seems that my application is “stuck” (actually it runs that loop) and after a while it updates the back-color of ALL THE LABLES at once.

Why it doesn’t update each label at a time?
It makes the “user” think that the application got stuck.
Here’s my code:

        Private Sub btnActivateMonitor_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnActivateMonitor.Click
        Dim xmldoc As New XmlDataDocument()
    Dim xmlnode As XmlNodeList
    Dim fs As New FileStream(acXmlFileName, FileMode.Open, FileAccess.Read)
    Dim i As Integer

    Dim name As String
    Dim lbl As String
    Dim ip As String

    xmldoc.Load(fs)
    xmlnode = xmldoc.GetElementsByTagName("Unit")
    For i = 0 To xmlnode.Count - 1
        name = xmlnode(i).ChildNodes.Item(0).InnerText.Trim()
        lbl = xmlnode(i).ChildNodes.Item(1).InnerText.Trim()
        ip = xmlnode(i).ChildNodes.Item(2).InnerText.Trim()

        checkUnitStatus(name, lbl, ip)
    Next
    End Sub
 Sub checkUnitStatus(ByVal name As String, ByVal lbl As String, ByVal ip As String)
     rtbLog.Text = rtbLog.Text & TimeValue(Now) & " Checking ..." & name & "(" & ip & ") ..........."

    If sendPing(ip) Then
        Me.Controls(lbl).BackColor = Color.Green
        rtbLog.Text = rtbLog.Text & "success" & vbCrLf
    Else
        Me.Controls(lbl).BackColor = Color.Red
        rtbLog.Text = rtbLog.Text & "Failed" & vbCrLf
    End If
End Sub
'+--------------------------------------
'|  Send Ping (ip)
'+-------------------------------------- 
Function sendPing(ByVal ip As String)
    Dim reachable As Boolean = False
    Try
        reachable = My.Computer.Network.IsAvailable AndAlso _
                    My.Computer.Network.Ping(ip, 10000)
    Catch pingException As System.Net.NetworkInformation.PingException
    Catch genericNetworkException As System.Net.NetworkInformation.NetworkInformationException
        ' Fail silently and return false
    End Try
    Return reachable
End Function

Answer 1

you should refresh the ui inside the Loop.
ie after calling checkUnitStatus

   checkUnitStatus(name, lbl, ip) 
   Me.Controls(lbl).Refresh()
Next