Updating Processes

[ForumDoe]

I've been looking at different ways of getting processes and updating them. I first looked at WMI and then decided to just use the Process Class.

I found some code on another web site that shows how to update processes in a ListBox. Ideally, I'd like to use a listview.

I've been trying for a couple of days on how to get this to work, but I've come up short. If you all can help me understand the process, I'd appreciate it.

The original poster created a class first and then updated the processes within a timer I believe. I tested it with a listbox, and it works well. The process is surprisingly smooth.

Class proc
        Public name As String
        Public Id As Integer
        Overrides Function ToString() As String
            Return name
        End Function
    End Class

Private Sub UpdateProcesses()
        proclist = Process.GetProcesses()
        For Each p As Process In proclist
            Dim p2 As New proc
            p2.name = p.ProcessName
            p2.Id = p.Id
            Dim add As Boolean = True
            For Each pr As proc In ListBox1.Items
                If (pr.Id = p.Id) Then
                    add = False
                End If
            Next
            If add Then
                ListBox1.Items.Add(p2)
            End If
        Next
        Dim l As New ListBox()
        Dim b As New ListBox.ObjectCollection(l, ListBox1.Items)
        For Each p As proc In b
            Try
                Dim p2 As Process = Process.GetProcessById(p.Id)
                Dim s = p2.ProcessName
            Catch ex As Exception
                ListBox1.Items.Remove(p)
            End Try
        Next
    End Sub

Thanks

[jmcilhinney]

So basically your only problem is adding information to a ListView, right? You've already got all the information.

First you would need to set the View property of the ListView to details, then add the columns in the designer. At run time, to add an item to the ListView you first create a ListViewItem with the text for the first column, then add ListViewSubItems to that for the other columns, then add the item to the control's Items collection.

I have to say, using exceptions to prompt removal of items is poor form, and there's really no need anyway. You're getting all the process each time anyway. You should simply clear the Items collection of the control each time and completely repopulate it. There would have to be a lot of processes for you to notice any lag and it would probably still perform better than throwing exceptions anyway.

E.g.

Me.ListView1.BeginUpdate()
Me.ListView1.Items.Clear()

Dim item As ListViewItem

For Each p In Process.GetProcesses()
    item = New ListViewItem(p.Id.ToString())
    item.SubItems.Add(p.ProcessName)
    Me.ListView1.Items.Add(item)
Next

Me.ListView1.EndUpdate()

[ForumDoe]

I guess the thing I'm having a hard time figuring out is the ObjectCollection he declares with the variable, b.

What would be the counterpart for a listview?

I tried redoing the code to something like this:

proclist = Process.GetProcesses()
        For Each p As Process In proclist
            Dim p2 As New proc
            p2.name = p.ProcessName
            p2.Id = p.Id
            Dim add As Boolean = True
            For Each pr As proc In ListView1.Items
                If (pr.Id = p.Id) Then
                    add = False
                End If
            Next
            If add Then
                Dim lvi As ListViewItem = New ListViewItem
                lvi.Text = (p2.ToString)
                ListView1.Items.Add(lvi)
            End If
        Next
        Dim l As New Listview()
        Dim b As New ListView.ListViewItemCollection(l, [B]ListView1.Items[/B])
        For Each p As proc In b
            Try
                Dim p2 As Process = Process.GetProcessById(p.Id)
                Dim s = p2.ProcessName
            Catch ex As Exception
                ListView1.Items.Remove([B]p[/B])
            End Try
        Next

The bold lines are the two issues throwing exceptions.

The first error states: Too many arguments to 'Public Sub New(owner as System.Windows.Forms.Listview)'.

Second error: Value of type 'WindowsApplication1.proc' cannot be converted to 'System.Windows.Forms.ListviewItem'.

The second error appeared after I changed the ListboxObjectCollection to ListViewItemCollection. So, I imagine after I fix that, it should resolve itself.

I tired changing the first error to an ListViewItemCollection instead of .Items, but that didn't work.

Since the error states that there are too many arguments, I'd think that it could only have one variable passed to it since two seems like an "overload".

I tried taking out the variable l but that didn't work. I didn't think it would because it seems that it would need that variable for the newly declared ListView, though I don't understand why.

Also, my problem could be the ListViewItemCollection I changed from the ObjectCollection. It seemed like the appropriate counterpart, but I could be wrong. I was thinking that the ObjectCollection was a ListBox's way of getting a collection of items in the ListBox, so ListViewItemCollection seemed appropriate.

Thanks

[jmcilhinney]

I've got to say, looking at that code, it makes no sense. It's creating a new ListBox each time. That's just crazy. You don't need to create a new control so you don't need to create a new ObjectCollection or the equivalent thereto. You've already got a ListView control and that's all you need. Just work with the Items collection of that ListView.

[ForumDoe]

I thought it seemed odd that a new control was being created. That's what I didn't understand why it was being done.

I'll take it out, play around with it a little bit and see what I get.

[ForumDoe]

I modified the bottom half of the code to this:

For Each p As proc In ListView1.Items
            Try
                Dim p2 As Process = Process.GetProcessById(p.Id)
                Dim s = p2.ProcessName
            Catch ex As Exception
                ListView1.Items.Remove(p)
            End Try
        Next

I get an error on the p variable when trying to remove it from the list.

It says that proc cannot be converted to ListViewItem. I tried declaring p as a ListViewItem, but putting the code outside of the block hides the variable within an enclosing block. Putting it inside also does not work because the variable is already declared.

How would I be able to remove the item from the list?

Thanks

[jmcilhinney]

Here's some fairly efficient code that will work with a ListView. I'm posting it twice; once for readability and once for copy-and-paste-ability:

Private processesByID As New Dictionary(Of Integer, Process)
 
Private Sub Form1_Load(ByVal sender As System.Object, _
                       ByVal e As System.EventArgs) Handles MyBase.Load
    Me.RefreshProcessList()
End Sub
 
Private Sub Timer1_Tick(ByVal sender As System.Object, _
                        ByVal e As System.EventArgs) Handles Timer1.Tick
    Me.RefreshProcessList()
End Sub
 
Private Sub RefreshProcessList()
    'Create a dictionary of currently running processes keyed on their ID.
    Dim currentProcessesByID = Process.GetProcesses().ToDictionary(Function(p) p.Id)
 
    'Remove processes that are no longer running.
    For Each id In Me.processesByID.Keys.ToArray()
        If Not currentProcessesByID.ContainsKey(id) Then
            'This process is no longer running so destroy the Process object and remove it from the list.
            Me.processesByID(id).Dispose()
            Me.processesByID.Remove(id)
        End If
    Next
 
    'Add new processes.
    For Each id In currentProcessesByID.Keys
        If Me.processesByID.ContainsKey(id) Then
            'This process is already in the list so destroy the duplicate.
            currentProcessesByID(id).Dispose()
        Else
            'This is a new process so add it to the list.
            Me.processesByID.Add(id, currentProcessesByID(id))
        End If
    Next
 
    'Update the list view.
    Me.ListView1.BeginUpdate()
    Me.ListView1.Items.Clear()
 
    'Add an item for each current process.
    For Each id In Me.processesByID.Keys
        Me.ListView1.Items.Add(id.ToString()).SubItems.Add(Me.processesByID(id).ProcessName)
    Next
 
    Me.ListView1.EndUpdate()
End Sub

Private processesByID As New Dictionary(Of Integer, Process)

Private Sub Form1_Load(ByVal sender As System.Object, _
                       ByVal e As System.EventArgs) Handles MyBase.Load
    Me.RefreshProcessList()
End Sub

Private Sub Timer1_Tick(ByVal sender As System.Object, _
                        ByVal e As System.EventArgs) Handles Timer1.Tick
    Me.RefreshProcessList()
End Sub

Private Sub RefreshProcessList()
    'Create a dictionary of currently running processes keyed on their ID.
    Dim currentProcessesByID = Process.GetProcesses().ToDictionary(Function(p) p.Id)

    'Remove processes that are no longer running.
    For Each id In Me.processesByID.Keys.ToArray()
        If Not currentProcessesByID.ContainsKey(id) Then
            'This process is no longer running so destroy the Process object and remove it from the list.
            Me.processesByID(id).Dispose()
            Me.processesByID.Remove(id)
        End If
    Next

    'Add new processes.
    For Each id In currentProcessesByID.Keys
        If Me.processesByID.ContainsKey(id) Then
            'This process is already in the list so destroy the duplicate.
            currentProcessesByID(id).Dispose()
        Else
            'This is a new process so add it to the list.
            Me.processesByID.Add(id, currentProcessesByID(id))
        End If
    Next

    'Update the list view.
    Me.ListView1.BeginUpdate()
    Me.ListView1.Items.Clear()

    'Add an item for each current process.
    For Each id In Me.processesByID.Keys
        Me.ListView1.Items.Add(id.ToString()).SubItems.Add(Me.processesByID(id).ProcessName)
    Next

    Me.ListView1.EndUpdate()
End Sub

[ForumDoe]

Thanks, jmcilhinney.

Your example works, but there's a couple of problems. Although the flash I minimal, it still flashes when updates and flashes no matter if there is an update or not. Also when updating, the selected item loses focus and this is of course less than ideal.

I'll look some more into it and see what I get, but do you know what can be done to resolve this?

Thanks

[weirddemon]

Jmc, with the example you posted, couldn't you just add the items to the list to start with, and then add or delete them from the ListView instead of adding the list each time?

Wouldn't that remove the flicker?

It looks like you're adding and removing items to the dictionary. Then you're adding the whole dictionary to the ListView. From what I'm seeing, you're adding all of the processes each time. It's still removing and adding appropriate processes, but it's adding all of them, instead of just the ones needed.

I could be wrong though

[jmcilhinney]

Jmc, with the example you posted, couldn't you just add the items to the list to start with, and then add or delete them from the ListView instead of adding the list each time?

Wouldn't that remove the flicker?

It looks like you're adding and removing items to the dictionary. Then you're adding the whole dictionary to the ListView. From what I'm seeing, you're adding all of the processes each time. It's still removing and adding appropriate processes, but it's adding all of them, instead of just the ones needed.

I could be wrong though

You are correct that that is what my code is doing. Whether or not making the change you suggest would remove the flicker I don't know, but it may well do.