C# Signature:

[DllImport("user32.dll")]

[return: MarshalAs(UnmanagedType.Bool)]

static extern bool EnumThreadWindows(uint dwThreadId, EnumThreadDelegate lpfn, IntPtr lParam);

vb Signature:

<DllImport("user32.dll")>_

Friend Shared Function EnumThreadWindows(dwThreadId as Int32, lpfn as EnumThreadDelegate, lParam as IntPtr) as Boolean

End Function

User-Defined Types:

public delegate bool EnumThreadDelegate (IntPtr hwnd, IntPtr lParam);

Notes:

None.

Tips & Tricks:

Please add some!

Sample Code:

[C#]

using System;

using System.Drawing;

using System.Collections;

using System.ComponentModel;

using System.Windows.Forms;

using System.Data;

using System.Diagnostics;

using System.Runtime.InteropServices;

using System.Threading;

namespace ExitApp

{

    public class ExitApp
    {
    private const UInt32 WM_CLOSE = 0x0010;

    public delegate bool EnumThreadDelegate (IntPtr hWnd, IntPtr lParam);

    [DllImport("user32.dll")]
    static extern bool EnumThreadWindows(uint dwThreadId, EnumThreadDelegate lpfn, IntPtr lParam);

    [DllImport("user32.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    static extern bool PostMessage(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);

    [STAThread]
    static void Main(string[] args)
    {
        // Find process.
        Process[] p = Process.GetProcessesByName(args[0]);

        if (p.Length > 0)
        {
        foreach(Process proc in p)
        {
            // Check if main window exists. If the window is minimized to the tray this might be not the case.
            if (proc.MainWindowHandle == IntPtr.Zero)
            {
            // Try closing application by sending WM_CLOSE to all child windows in all threads.
            foreach (ProcessThread pt in proc.Threads)
            {
                EnumThreadWindows((uint) pt.Id, new EnumThreadDelegate(ExitApp.EnumThreadCallback), IntPtr.Zero);
            }
            }
            else
            {
            // Try to close main window.
            if(proc.CloseMainWindow())
            {
                // Free resources used by this Process object.
                proc.Close();
            }
            }
        }
        }
    }

    static bool EnumThreadCallback(IntPtr hWnd, IntPtr lParam)
    {
        // Close the enumerated window.
        PostMessage(hWnd, WM_CLOSE, IntPtr.Zero, IntPtr.Zero);

        return true;
    }
    }

}

[VisualBasic.Net]

Imports System

Imports System.Drawing

Imports System.Collections

Imports System.ComponentModel

Imports System.Windows.Forms

Imports System.Data

Imports System.Diagnostics

Imports System.Runtime.InteropServices

Imports System.Threading

Public Class ExitApp

   Private Const WM_CLOSE As UInt32 = &H10

   Delegate Function EnumThreadDelegate(hWnd As IntPtr, lParam As IntPtr) As Boolean

   <DllImport("user32.dll")>  _
   Shared Function EnumThreadWindows(dwThreadId As UInteger, lpfn As EnumThreadDelegate, lParam As IntPtr) As Boolean

   <DllImport("user32.dll", SetLastError := True)>  _
   Shared Function PostMessage(hWnd As IntPtr, Msg As UInteger, wParam As IntPtr, lParam As IntPtr) As<MarshalAs(UnmanagedType.Bool)> Boolean

   Public Overloads Shared Sub Main()
     Main(System.Environment.GetCommandLineArgs())
   End Sub

   <STAThread()>  _
   Overloads Shared Sub Main(args() As String)
     Dim processName As String

     ' Find process.
     Dim p As Process() = Process.GetProcessesByName(args(0))

     If p.Length > 0 Then
       For Each proc As Process In p
     ' Check if main window exists. If the window is minimized to the tray this might be not the case.
     If proc.MainWindowHandle = IntPtr.Zero Then
       ' Try closing application by sending WM_CLOSE to all child windows in all threads.
       For Each pt As ProcessThread In proc.Threads
     EnumThreadWindows(CUInt(pt.Id), New EnumThreadDelegate(ExitApp.EnumThreadCallback), IntPtr.Zero)
       Next pt
     Else
       ' Try to close main window.
       If proc.CloseMainWindow() Then
     ' Free resources used by this Process object.
     proc.Close()
       End If
     End If
       Next proc
     End If
   End Sub

   Shared Function EnumThreadCallback(hWnd As IntPtr, lParam As IntPtr) As Boolean
     ' Close the enumerated window.
     PostMessage(hWnd, WM_CLOSE, IntPtr.Zero, IntPtr.Zero)

     Return True
   End Function

End Class