In my post Multithreading pings and showing them in a grid in VB.Net I got a question from Alex.


What if I want to check 100 ip’s 5 at a time? What do I need to change in the code to accomplish this. I’ve been working on it for several hours with no luck.

And Alex was pushing his luck by coming back and asking this too.

Will it also be possible to pause/resume checking as this would be handy?

But I aim to please so I did what Alex wanted.

The app pings 6 Ip-addresses in groups of 2 in an Async matter.

You can pause the pings, and it will stop/pause as soon as it is finished with the 2 it was pinging.

I just added 2 extra menu items.

It just starts when you click Ping.

And it pauses when you click Pause.

And here is the enormous amount of code.

```vbnet Imports System.Threading Imports System.Threading.Tasks Imports System.Net.NetworkInformation

Partial Public Class Form1

Private fThread As Thread
Private fThread2 As Thread
Private waitHandle As ManualResetEvent = New ManualResetEvent(True)

Public Delegate Sub AddRowDelegate(ByVal column As Integer)
Delegate Sub CheckOnlineDelegate(ByVal rowindex As Integer)
Delegate Sub SetOnlineDelegate(ByVal rowindex As Integer)

Private success As New List(Of Integer)
Private done As New List(Of Integer)

Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    fGrid.Columns.Add("Ip", "Ip")
    fGrid.Columns.Add("Ping", "Ping")
    fGrid.Columns(0).Width = 100
    fGrid.Columns(1).AutoSizeMode = DataGridViewAutoSizeColumnMode.Fill
    For i As Integer = 0 To 5
        Dim myRowIndex = fGrid.Rows.Add()
        fGrid.Rows(myRowIndex).Cells(0).Value = "10.216.110." & (11 + myRowIndex).ToString
End Sub

Private Sub ThreadProc()
    For i As Integer = 0 To 2
        Parallel.For(0 + (i * 2), 2 + (i * 2), Sub(b)
                                                   Do While Not done.Contains(b)
                                                       fGrid.Invoke(New AddRowDelegate(AddressOf AddRow), New Object() {b})
                                                   fGrid.Invoke(New SetOnlineDelegate(AddressOf SetOnline), New Object() {b})
                                               End Sub)
End Sub

Private Sub ThreadProc2()
    For i As Integer = 0 To 2
        Parallel.For(0 + (i * 2), 2 + (i * 2), Sub(b)
                                               End Sub)
End Sub

Private Sub AddRow(ByVal rowindex As Integer)
    If fGrid.Rows(rowindex).Cells(1).Value Is Nothing OrElse fGrid.Rows(rowindex).Cells(1).Value.ToString.Contains(".....") OrElse Not fGrid.Rows(rowindex).Cells(1).Value.ToString.Contains("Pinging") Then
        fGrid.Rows(rowindex).Cells(1).Value = "Pinging 10.216.110." & (11 + rowindex).ToString & " "
        fGrid.Rows(rowindex).Cells(1).Value = fGrid.Rows(rowindex).Cells(1).Value.ToString & "."
    End If
    fGrid.Rows(rowindex).Cells(1).Style.BackColor = Drawing.Color.White
End Sub

Private Sub CheckOnline(ByVal rowindex As Integer)
    Dim _ping As New Ping
        Dim _pingreply = _ping.Send("10.216.110." & (11 + rowindex).ToString, 2000)
        If _pingreply.Status = IPStatus.Success Then
            SyncLock success
            End SyncLock
        End If
    Catch ex As Exception
    End Try
    SyncLock done
    End SyncLock
End Sub

Private Sub SetOnline(ByVal rowindex As Integer)
    If Not success.Contains(rowindex) Then
        fGrid.Rows(rowindex).Cells(1).Value = "Offline"
        fGrid.Rows(rowindex).Cells(1).Style.BackColor = Drawing.Color.Red
        fGrid.Rows(rowindex).Cells(1).Value = "Online"
        fGrid.Rows(rowindex).Cells(1).Style.BackColor = Drawing.Color.Green
    End If
End Sub

Private Sub PingToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles PingToolStripMenuItem.Click
    done = New List(Of Integer)
    success = New List(Of Integer)
    fThread = New Thread(New ThreadStart(AddressOf ThreadProc))
    fThread.IsBackground = True
    fThread2 = New Thread(New ThreadStart(AddressOf ThreadProc2))
    fThread2.IsBackground = True
End Sub

Private Sub StopToolStripMenuItem_Click(sender As System.Object, e As System.EventArgs) Handles StopToolStripMenuItem.Click
End Sub

Private Sub ResumeToolStripMenuItem_Click(sender As System.Object, e As System.EventArgs) Handles ResumeToolStripMenuItem.Click
End Sub

End Class``` Not pretty, but functional. I used the ManualResetEvent to Pause and resume the pings and I just added an extra for next to the Threadprocs to make the grouping happen.

All quite simple if you know how.