Constantly monitor if a process is running - vb.net

Question

I have the following code:
Dim p() As Process
Private Sub CheckIfRunning()
p = Process.GetProcessesByName("skype") 'Process name without the .exe
If p.Count > 0 Then
' Process is running
MessageBox.Show("Yes, Skype is running")
Else
' Process is not running
MessageBox.Show("No, Skype isn't running")
End If
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
CheckIfRunning()
End Sub
And it works GREAT!
But I'm wondering how I would convert this to a monitoring application, to constantly check if the processes is running. Is it as simple as putting the check on a timer every 1 second, or is there a better, more efficient way to go about this.
In the end result, I'd like to have a label that says "Running", or "Not Running" based on the process, but I need something to watch the process constantly.

Answer 1

If you need the app running all the time, then you don't need a Timer at all. Subscribe to the Process.Exited() event to be notified when it closes. For instance, with Notepad:
Public Class Form1
Private P As Process
Private FileName As String = "C:\Windows\Notepad.exe"
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim ps() As Process = Process.GetProcessesByName(Path.GetFileNameWithoutExtension(FileName))
If ps.Length = 0 Then
P = Process.Start(FileName)
P.EnableRaisingEvents = True
AddHandler P.Exited, AddressOf P_Exited
Else
P = ps(0)
P.EnableRaisingEvents = True
AddHandler P.Exited, AddressOf P_Exited
End If
End Sub
Private Sub P_Exited(sender As Object, e As EventArgs)
Console.WriteLine("App Exited # " & DateTime.Now)
Console.WriteLine("Restarting app: " & FileName)
P = Process.Start(FileName)
P.EnableRaisingEvents = True
AddHandler P.Exited, AddressOf P_Exited
End Sub
End Class
That would keep it open all the time, assuming you wanted to open it if it wasn't already running.
If you don't want to open it yourself, and need to detect when it does open, then you could use WMI via the ManagementEventWatcher as in this previous SO question.

Answer 2

I've done something similar to this to monitor an exe that I need to be running all the time, and to restart it if it was down.
Mine was running as a Windows Service - that way it would start when windows booted and id never need to look after it.
Alternatively you could just create it as a console app and put it in your startup folder?
I had:
Sub Main()
Do
Check_server()
Dim t As New TimeSpan(0, 15, 0)
Threading.Thread.Sleep(t)
Loop
End Sub
Public Sub Check_server()
Dim current_pros() As Process = get_pros()
Dim found As Boolean = False
If Now.Hour < "22" Then
For Each pro In current_pros
If pro.ProcessName.ToLower = "Lorraine" Then
found = True
Exit For
Else
found = False
End If
Next
If found Then
Console.WriteLine("Server up")
Else
Console.WriteLine("Server down - restarting")
restart_server()
End If
End If
End Sub
My "server" app was called Lorraine...Also a timer maybe better practice than having the thread sleep..

Answer 3

From my experience, a simple timer works best:
'Timer interval set to 1-5 seconds... no remotely significant CPU hit
Private Sub timerTest_Tick(sender As System.Object, e As System.EventArgs) Handles timerTest.Tick
Dim p() As Process = Process.GetProcessesByName("Skype")
lblStatus.Text = If(p.Length > 0, "Skype is running.", "Skype isn't running.")
End Sub
Your mileage may vary, but I don't like to deal with separate threads unless necessary.