How to bring the app to front, if already open? My app is Windows Form application c#

How to bring app to front, if already open?

Accepted answer

KOZ6.0 6,130

I've rewritten my answer.Thank you, for Viorel.

(1) Create a class containing Pinvoke declarations.

using System.Runtime.InteropServices;

internal class NativeMethods
{
    public const int HWND_BROADCAST = 0xffff;

    public static int WM_WAKEUP_WINDOW = 
        RegisterWindowMessage("{28D5B089-B46F-4F69-99BE-6525596547E6}");

    [DllImport("user32.dll", CharSet = CharSet.Unicode)]
    public static extern bool PostMessage(IntPtr hWnd, int Msg,
                                          IntPtr wParam, IntPtr lParam);

    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    public static extern int RegisterWindowMessage(string lpString);

    [DllImport("User32")]
    public static extern bool SetForegroundWindow(IntPtr hWnd);
}

(2) Program.cs

using System.Diagnostics;
using System.Threading;

internal static class Program
{
    [STAThread]
    static void Main() {
        var current = Process.GetCurrentProcess();
        var mutex = new Mutex(true, current.ProcessName, out bool createdNew); ;
        if (createdNew) {
            try {
                ApplicationConfiguration.Initialize();
                Application.Run(new Form1());
            } finally {
                mutex.ReleaseMutex();
            }
        } else {
            NativeMethods.PostMessage(
                NativeMethods.HWND_BROADCAST, 
                        NativeMethods.WM_WAKEUP_WINDOW,
                        IntPtr.Zero, IntPtr.Zero);
        }
    }
}

(3) Form

protected override void WndProc(ref Message m) { 
    if (m.Msg == NativeMethods.WM_WAKEUP_WINDOW) {
        notifyIcon1.Visible = false;
        WindowState = FormWindowState.Normal;
        Show();
        NativeMethods.SetForegroundWindow(Handle);
        return;
    }
    base.WndProc(ref m);
}

Hussnain Fareed 20 Reputation points

2024-05-23T05:48:02.6433333+00:00

This works. But if the app hiding in the system tray, then it's not working.
What's the solution to it?

KOZ6.0 6,130

But if the app hiding in the system tray, then it's not working.

Does this mean it's minimized?

public static void WakeupWindow(IntPtr hwnd) {
    if (IsIconic(hwnd)) {
        ShowWindow(hwnd, SW_RESTORE);
    }
    SwitchToThisWindow(hwnd, true);
}

[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool IsIconic(IntPtr hWnd);

private const int SW_RESTORE = 9;

[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool ShowWindow(IntPtr hWnd, int nCmdShow);

[DllImport("user32.dll", SetLastError = true)]
private static extern void SwitchToThisWindow(IntPtr hWnd, bool fAltTab);

Hussnain Fareed 20

Not working...
To send my app to system tray I'm doing this, Because I also need minimize functionality separately.

private void btn_Close_Click(object sender, EventArgs e)
{
    this.Hide();
    notifyIcon1.Visible = true;
}

private void notifyIcon1_Click(object sender, EventArgs e)
{
    notifyIcon1.Visible = false;
    this.Show();
}

private void Layout_Load(object sender, EventArgs e)
{
    notifyIcon1.Visible = false;
}

Hussnain Fareed 20

I added extra code in answer provided by "KOZ6.0" and this works great.

else
{
    var prevInstance = Process.GetProcessesByName(current.ProcessName)
                        .Where(p => p.Id != current.Id).FirstOrDefault();
    IntPtr hwnd = prevInstance.MainWindowHandle;
    //when the window is hidden, the hwnd = IntPtr.Zero
    if (hwnd == IntPtr.Zero)
    {
        //window is hidden, find it by the title
        //"Form1" is the title that is displayed on the Window
        hwnd = FindWindowA(null, "From1");
        ShowWindow(hwnd, SW_NORMAL);
    }
    if (prevInstance != null)
    {
        SwitchToThisWindow(hwnd, true);
    }
}

KOZ6.0 6,130 Reputation points

2024-05-23T10:07:05.2933333+00:00

If you hide the window, MainWindowHandle will be zero. Therefore, need a mechanism to restore the window.

Please refer to Viorel's comment.
Hussnain Fareed 20 Reputation points

2024-05-23T10:18:24.7333333+00:00

I added some extra code in your answer and it works. I tested Virol's answer and it also works best. Now I'm analyzing which to opt.
Hussnain Fareed 20 Reputation points

2024-05-23T10:30:27.9066667+00:00

Viorel , KOZ6.0, anyone of you help which code is now more best
KOZ6.0 6,130 Reputation points

2024-05-23T11:07:54.44+00:00

If you have multiple target processes, it is a good idea to broadcast a message and have them respond. . Since FindWindow may retrieve the window of another process, it is better to use EnumWindows and GetWindowThreadProcessId to check the ID of the process to which the window belongs.

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How to bring app to front, if already open?

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