Recuperare l’id del processo padre

Prendendo spunto da un post apparso sul newsgroup dedicato a Visual Basic (http://social.msdn.microsoft.com/Forums/it-IT/visualbasicit/threads), vorrei proporvi un metodo di estensione per la classe Process che, utilizzando P/Invoke, recupera l’identificativo del processo padre di un processo (se esiste), cioè l’identificativo del processo che ha aperto il processo.

Il modulo che definisce il metodo di estensione è il seguente:

1. Imports System.Runtime.InteropServices
2. Imports System.Runtime.CompilerServices
3.  
4. Public Module ProcessExtension
5.     <DllImport("kernel32.dll", SetLastError:=True)>
6.     Private Function CreateToolhelp32Snapshot(ByVal dwFlags As SnapshotFlags, ByVal th32ProcessID As UInteger) As IntPtr
7.     End Function
8.  
9.     <DllImport("kernel32.dll")> _
10.     Private Function Process32First(ByVal hSnapshot As IntPtr, ByRef lppe As PROCESSENTRY32) As Boolean
11.     End Function
12.  
13.     <DllImport("kernel32.dll")> _
14.     Private Function Process32Next(ByVal hSnapshot As IntPtr, ByRef lppe As PROCESSENTRY32) As Boolean
15.     End Function
16.  
17.  
18.     <Flags()> _
19.     Private Enum SnapshotFlags As Integer
20.         HeapList = &H1
21.         Process = &H2
22.         Thread = &H4
23.         [Module] = &H8
24.         Module32 = &H10
25.         Inherit = &H80000000
26.         All = &H1F
27.     End Enum
28.  
29.     <StructLayout(LayoutKind.Sequential)> _
30.     Private Structure PROCESSENTRY32
31.         Public dwSize As UInteger
32.         Public cntUsage As UInteger
33.         Public th32ProcessID As UInteger
34.         Public th32DefaultHeapID As IntPtr
35.         Public th32ModuleID As UInteger
36.         Public cntThreads As UInteger
37.         Public th32ParentProcessID As UInteger
38.         Public pcPriClassBase As Integer
39.         Public dwFlags As UInteger
40.         <VBFixedString(260), MarshalAs(UnmanagedType.ByValTStr, SizeConst:=260)> Public szExeFile As String
41.     End Structure
42.  
43.     <Extension()>
44.     Public Function GetParentProcessID(ByVal process As Process) As UInteger?
45.         If process Is Nothing Then Throw New NullReferenceException()
46.         Dim retval As UInteger? = Nothing
47.         Dim snapShot = CreateToolhelp32Snapshot(SnapshotFlags.Process, 0)
48.         If snapShot <> IntPtr.Zero Then
49.             Dim procEntry As New PROCESSENTRY32
50.             procEntry.dwSize = CUInt(Marshal.SizeOf(GetType(PROCESSENTRY32)))
51.             Dim okFlag = Process32First(snapShot, procEntry)
52.             While (okFlag)
53.                 If process.Id = procEntry.th32ProcessID Then
54.                     retval = procEntry.th32ParentProcessID
55.                     Exit While
56.                 Else
57.                     okFlag = Process32Next(snapShot, procEntry)
58.                 End If
59.             End While
60.         End If
61.         Return retval
62.     End Function
63. End Module

Grazie al metodo di estensione possiamo semplicemente scrivere

1. .
2. Dim parentId = Process.GetCurrentProcess.GetParentProcessID()
3. .
4. .

 

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