About Chris Expertise I can answer pretty much any question relating to VB.NET and its use in a Windows environment. I specialize in ASP.NET web development and MSSQL database access.
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Expert: Chris Date: 9/12/2007 Subject: Reading Active Applications from Task Manager.
Question Hi,
I need to read the active applications from task manager(Applications tab) and populate it into a list box.On clicking the value in list box the particular application should become active.I am using Visual studio 2003.
Any help will be appreciated.
Thanks,
Suhani
Answer Hi,
As far as I know, you can only do this with programs that have a MainWindowHandle. Most of the programs you see in the Applications list in Task Manager do not have a main window, or at least they are hidden from the .NET Framework.
For those that do provide a window handle, it's relatively easy to do what you want. Create a new Form (I named it Form1) and use the following code, it should get you started:
'--[ begin Form1.vb ]--
Imports System.Diagnostics
Public Class Form1
Private Sub ListBox1_DoubleClick(ByVal sender As Object, ByVal e As System.EventArgs) Handles ListBox1.DoubleClick
If Not (ListBox1.SelectedItem Is Nothing) Then
Dim objProcess As MyProcInfo = DirectCast(ListBox1.SelectedItem, MyProcInfo)
If Not (objProcess.ProcInfo.MainWindowHandle = IntPtr.Zero) Then
Dim hWnd As IntPtr = objProcess.ProcInfo.MainWindowHandle
If IsIconic(hWnd) Then ShowWindowAsync(hWnd, SW_RESTORE)
SetForegroundWindow(hWnd)
End If
End If
End Sub
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim arrProcesses As Process() = Process.GetProcesses()
ListBox1.Items.Clear()
For i As Integer = 0 To arrProcesses.Length - 1
Dim objProcess As Process = arrProcesses(i)
If Not (objProcess.MainWindowHandle = IntPtr.Zero) Then ListBox1.Items.Add(New MyProcInfo(objProcess))
Next
End Sub
Private Class MyProcInfo
Public ProcInfo As Process
Private Sub New()
End Sub
Public Sub New(ByVal objProcInfo As Process)
ProcInfo = objProcInfo
End Sub
Public Overrides Function ToString() As String
Return DirectCast(IIf((ProcInfo.MainWindowHandle = IntPtr.Zero), "", "* "), String) & ProcInfo.ProcessName & " (" & ProcInfo.Id & ")"
End Function
End Class
End Class
'--[ end Form1.vb ]--
You'll also need to add a new code Module to your project, with some API call wrappers you'll need to get these process windows to show themselves and be set to the foreground:
'--[ begin APICalls.vb ]--
Imports System.Runtime.InteropServices
Module APICalls
<DllImport("user32.dll")> _
Function SetForegroundWindow(ByVal hWnd As IntPtr) As Boolean
End Function
<DllImport("user32.dll")> _
Function ShowWindowAsync(ByVal hWnd As IntPtr, ByVal nCmdShow As Integer) As Boolean
End Function
<DllImport("user32.dll")> _
Function IsIconic(ByVal hWnd As IntPtr) As Boolean
End Function
Public Const SW_HIDE As Integer = 0
Public Const SW_SHOWNORMAL As Integer = 1
Public Const SW_SHOWMINIMIZED As Integer = 2
Public Const SW_SHOWMAXIMIZED As Integer = 3
Public Const SW_SHOWNOACTIVATE As Integer = 4
Public Const SW_RESTORE As Integer = 9
Public Const SW_SHOWDEFAULT As Integer = 10
End Module
'--[ end APICalls.vb ]--
