[RESOLVED] Threaded Ping

Hi

Ive got an app that holds a list of site we have, At each site there are a few devices.

The idea is when they click on a site all the details for the site are loaded and then a second thread sits and pings each device to see if its live. Im trying to do this in a seperate thread so if they click another site while its still pinging them it doesn't wait before it switches site.

This all seems to be workling fine except if you click through the sites quickly, when you do that it will eventually come up with

Quote:

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{"Collection was modified; enumeration operation might not execute."}

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Ive been struggling to work out how to fix this so any help would be great

the error flags up on the "Next" line in "ThreadedPing"

Thread stuff

Code:

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    Public Sub ThreadedPing(ByVal dt As DataTable)
        Try

            Dim dr As DataRow

            For Each dr In dt.Rows
                dr("Ping") = PingaLing(dr("DeviceIP"))
            Next
            frmMain.lstS1AttDev.DataSource = dt
            frmMain.lstS1AttDev.Splits(0).DisplayColumns(0).Width = frmMain.lstS1AttDev.Width / 4
            frmMain.lstS1AttDev.Splits(0).DisplayColumns(1).Width = frmMain.lstS1AttDev.Width / 4
            frmMain.lstS1AttDev.Splits(0).DisplayColumns(2).Width = frmMain.lstS1AttDev.Width / 5
            frmMain.lstS1AttDev.Splits(0).DisplayColumns(3).Width = 0
            frmMain.lstS1AttDev.Splits(0).DisplayColumns(4).Width = frmMain.lstS1AttDev.Width / 5

        Catch abortException As ThreadAbortException
            Console.WriteLine(CType(abortException.ExceptionState, String))
        End Try

    End Sub

    Public Function PingaLing(ByVal strIPAdd As String) As String
        Dim dtstart As Date

        dtstart = Now

        Try
            My.Computer.Network.Ping(strIPAdd)

            Dim runLength As Global.System.TimeSpan = Now.Subtract(dtstart)

            PingaLing = runLength.Milliseconds & " ms"
        Catch ex As Exception
            PingaLing = "Cannot Find Host!"
        End Try

    End Function

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Welcome to the world of multithreading.
You try to enumerate a collection and at the same time another thread changes it in some way.

Before making some changes be sure to sync lock your thread critical object like this:

vb.net Code:

SyncLock  dt
    For Each dr In dt.Rows
        dr("Ping") = PingaLing(dr("DeviceIP"))
    Next
End SyncLock

cheers.

seems to stop the problem :thumb: