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Home » Tip Bank » .NET » C#
Language: .NET
Expertise: Beginner
Apr 18, 2016

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Minimizing All Open Windows

It is quite easy to minimize all currently opened windows with C#. All you need to know is a few APIs:

FindWindow
SendMessageTimeout

Here is a small example:

public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
[DllImport("user32.dll", EntryPoint = "FindWindow", SetLastError = true)]
static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
[DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
static extern IntPtr SendMessageTimeout(
IntPtr windowHandle,
uint Msg,
IntPtr wParam,
IntPtr lParam,
SendMessageTimeoutFlags flags,
uint timeout,
out IntPtr result);

[Flags]
enum SendMessageTimeoutFlags : uint
{
SMTO_NORMAL = 0x0,
SMTO_BLOCK = 0x1,
SMTO_ABORTIFHUNG = 0x2,
SMTO_NOTIMEOUTIFNOTHUNG = 0x8
}

const int WM_COMMAND = 0x111;
const int MIN_ALL = 419;
const int MIN_ALL_UNDO = 416;

private void button1_Click(object sender, EventArgs e)
{
IntPtr OutResult;
IntPtr lHwnd = FindWindow("Shell_TrayWnd", null);
SendMessageTimeout(lHwnd, WM_COMMAND, (IntPtr)MIN_ALL, IntPtr.Zero, SendMessageTimeoutFlags.SMTO_ABORTIFHUNG, 2000, out OutResult);
System.Threading.Thread.Sleep(2000);
SendMessageTimeout(lHwnd, WM_COMMAND, (IntPtr)MIN_ALL_UNDO, IntPtr.Zero, SendMessageTimeoutFlags.SMTO_ABORTIFHUNG, 2000, out OutResult);
}
}

It makes use of the above-mentioned APIs to send the MIN_ALL commands so that all windows become minimized, similar to what the 'Show Desktop' button on the TaskBar does.

Hannes du Preez
 
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