How to Retrieve All Windows Associated with a Specific Process in .NET?

Retrieving All Windows Belonging to a Specific Process in .NET

Enumerating all windows associated with a particular process is a crucial task for various automation and inter-process communication scenarios. In .NET, this can be achieved by leveraging the EnumThreadWindows API, which enables the iteration through all windows created by a specific thread.

To enumerate windows belonging to a process based on its process ID (PID), follow these steps:

1. Import the necessary DLL: [DllImport("user32.dll")]
2. Define a delegate to handle the enumeration: delegate bool EnumThreadDelegate(IntPtr hWnd, IntPtr lParam)
3. Create an IEnumerable to store the window handles: var handles = new List()

4. Iterate through all threads of the target process using EnumThreadWindows:

   foreach (ProcessThread thread in Process.GetProcessById(processId).Threads)
        EnumThreadWindows(thread.Id, 
            (hWnd, lParam) => { handles.Add(hWnd); return true; }, IntPtr.Zero);

Example Usage:

Here's an example of using the EnumerateProcessWindowHandles method to retrieve the window titles of all windows created by the Windows Explorer process:

using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;

public class Program
{
    const uint WM_GETTEXT = 0x000D;

    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, int wParam, 
        StringBuilder lParam);

    [STAThread]
    static void Main(string[] args)
    {
        foreach (var handle in EnumerateProcessWindowHandles(
            Process.GetProcessesByName("explorer").First().Id))
        {
            StringBuilder message = new StringBuilder(1000);
            SendMessage(handle, WM_GETTEXT, message.Capacity, message);
            Console.WriteLine(message);
        }
    }

    static IEnumerable<IntPtr> EnumerateProcessWindowHandles(int processId)
    {
        var handles = new List<IntPtr>();

        foreach (ProcessThread thread in Process.GetProcessById(processId).Threads)
            EnumThreadWindows(thread.Id, 
                (hWnd, lParam) => { handles.Add(hWnd); return true; }, IntPtr.Zero);

        return handles;
    }
}

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