tommy.blog

2006-05-20

Getting a list of all the open windows

Here's some code you can use to get a list of all the open windows. Actually, you get a dictionary where each item is a KeyValuePair where the key is the handle (hWnd) of the window and the value is its title.

using HWND = IntPtr;
/// <summary>Contains a method to get all the open windows.</summary>
public static class OpenWindowGetter
{
    /// <summary>Returns a dictionary that contains the handle and title of all the open windows.</summary>
    /// <returns>A dictionary that contains the handle and title of all the open windows.</returns>
    public static IDictionary<HWND, string> GetOpenWindows()
    {
        HWND lShellWindow = GetShellWindow();
        Dictionary<HWND, string> lWindows = new Dictionary<HWND, string>();

        EnumWindows(delegate(HWND hWnd, int lParam)
        {
            if (hWnd == lShellWindow) return true;
            if (!IsWindowVisible(hWnd)) return true;

            int lLength = GetWindowTextLength(hWnd);
            if (lLength == 0) return true;

            StringBuilder lBuilder = new StringBuilder(lLength);
            GetWindowText(hWnd, lBuilder, lLength + 1);

            lWindows[hWnd] = lBuilder.ToString();
            return true;
            
        }, 0);

        return lWindows;
    }

    delegate bool EnumWindowsProc(HWND hWnd, int lParam);

    [DllImport("USER32.DLL")]
    static extern bool EnumWindows(EnumWindowsProc enumFunc, int lParam);

    [DllImport("USER32.DLL")]
    static extern int GetWindowText(HWND hWnd, StringBuilder lpString, int nMaxCount);

    [DllImport("USER32.DLL")]
    static extern int GetWindowTextLength(HWND hWnd);

    [DllImport("USER32.DLL")]
    static extern bool IsWindowVisible(HWND hWnd);

    [DllImport("USER32.DLL")]
    static extern IntPtr GetShellWindow();
}

And here's some code that uses it:

foreach(KeyValuePair<IntPtr, string> lWindow in OpenWindowGetter.GetOpenWindows())
{
    IntPtr lHandle = lWindow.Key;
    string lTitle = lWindow.Value;

    Console.WriteLine("{0}: {1}", lHandle, lTitle);
}

Tags: C#, Windows Forms.

# posted @ 11:53

Comments:

What on earth does this do?

EnumWindows(delegate(HWND hWnd, int lParam)
{
if (hWnd == lShellWindow) return true;
if (!IsWindowVisible(hWnd)) return true;

int lLength = GetWindowTextLength(hWnd);
if (lLength == 0) return true;

StringBuilder lBuilder = new StringBuilder(lLength);
GetWindowText(hWnd, lBuilder, lLength + 1);

lWindows[hWnd] = lBuilder.ToString();
return true;

}, 0);

Thanks,
Curtis

# posted by

Anonymous : 27 June, 2006 23:45

EnumWindows is a Win32 function that has 2 arguments. The first is a pointer to a function that is called for each window that is open. The second is a parameter that is passed as data to the function.
What you see above is that I use an anonymous delegate instead of a function pointer. The block of code is called for each open window. You could consider EnumWindows to be like a foreach-loop:
foreach(HWND hWnd in OpenWindows)
{
...
}

# posted by

Tommy Carlier : 28 June, 2006 07:29

I have not written any C++ in a while and I do not know the differences between c++ and C#. Can you tell me if this code will work with C++ or does it require C#.

Thank you.

# posted by

Anonymous : 18 August, 2006 19:38

Since it's just plain Win32, it will also work in C++.
You won't have to declare the static extern functions, imported from User32.dll, and instead of passing a delegate to EnumWindows, you will have to pass a function pointer. You will also have to replace the StringBuilder with a char array or a char pointer.
Here's the documentation for EnumWindows: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/windowing/windows/windowreference/windowfunctions/enumwindows.asp.
And here is some sample code I just found via Google: http://simplesamples.info/Windows/EnumWindows.php.

# posted by

Tommy Carlier : 19 August, 2006 09:54

How to get all the windows from multiple monitors?

# posted by

Emersion : 14 July, 2008 06:22

I thought this would get the list of open windows across multiple monitors. I'll check later today at work where I have 2 monitors.

# posted by

Tommy Carlier : 14 July, 2008 07:17

thanks for the code, It was hard to find, then I wanna give my contribution

here the code ready to use on C# 2008 (Net 3.5)

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

public static class OpenWindowGetter
{

public static IDictionary<IntPtr, String> GetOpenWindows()
{

IntPtr lShellWindow = GetShellWindow();
Dictionary<IntPtr, string> lWindows = new Dictionary<IntPtr, string>();

EnumWindows(delegate(IntPtr hWnd, int lParam)
{
if (hWnd == lShellWindow) return true;
if (!IsWindowVisible(hWnd)) return true;

int lLength = GetWindowTextLength(hWnd);
if (lLength == 0) return true;

StringBuilder lBuilder = new StringBuilder(lLength);
GetWindowText(hWnd, lBuilder, lLength + 1);

lWindows[hWnd] = lBuilder.ToString();
return true;

},0);

return lWindows;
}

delegate bool EnumWindowsProc(IntPtr hWnd, int lParam);

[DllImport("USER32.DLL")]
static extern bool EnumWindows(EnumWindowsProc enumFunc, int lParam);

[DllImport("USER32.DLL")]
static extern int GetWindowText(IntPtr hWnd, StringBuilder lpString, int nMaxCount);

[DllImport("USER32.DLL")]
static extern int GetWindowTextLength(IntPtr hWnd);

[DllImport("USER32.DLL")]
static extern bool IsWindowVisible(IntPtr hWnd);

[DllImport("USER32.DLL")]
static extern IntPtr GetShellWindow();
}

--David C

# posted by

David Castillo : 02 October, 2008 04:33

What's the difference with the original code? The only thing I see that is different is that you use IntPtr directory instead of the alias HWND.

# posted by

Tommy Carlier : 02 October, 2008 07:15

Thank you for this great example, but shouldn't

foreach(KeyValuePair lWindow = OpenWindowGetter.GetOpenWindows())

be

foreach(KeyValuePair lWindow in OpenWindowGetter.GetOpenWindows())

??
That's what made it work for me anyway.

Rick O.

# posted by

Anonymous : 29 June, 2010 17:15

Rick, thank you for the correction. You are absolutely correct. I'll fix it as soon as possible.

# posted by

Tommy Carlier : 29 June, 2010 17:33