Remove the window from the taskbar in WinUI 3

Question

I'm creating an app that needs UI but not show up inside the taskbar, I know exactly how to do this in, winforms and wpf, but the window object doesn't contain a ShowInTaskBar variable that I can just change.

I have tried NotifyIcon but that doesn't hide it from the taskbar, I also can't find any documentation on if this is even possible.

I only create a stack overflow question when I've spent more than 5 hours on this, so any help would be appreciated.

Answer 1

Nick showed me this post https://stackoverflow.com/a/551847/14724147

Just add the window handle to the win32 api and it will hide it from alt+tab and the taskbar

public MainWindow() 
{
    InitializeComponent();

    IntPtr hWnd = WindowNative.GetWindowHandle(this);
    int exStyle = (int)GetWindowLong(hWnd, (int)GetWindowLongFields.GWL_EXSTYLE);
    exStyle |= (int)ExtendedWindowStyles.WS_EX_TOOLWINDOW;
    SetWindowLong(hWnd, (int)GetWindowLongFields.GWL_EXSTYLE, (IntPtr)exStyle);
}

#region Window styles
[Flags]
public enum ExtendedWindowStyles
{
    // ...
    WS_EX_TOOLWINDOW = 0x00000080,
    // ...
}

public enum GetWindowLongFields
{
    // ...
    GWL_EXSTYLE = (-20),
    // ...
}

[DllImport("user32.dll")]
public static extern IntPtr GetWindowLong(IntPtr hWnd, int nIndex);

public static IntPtr SetWindowLong(IntPtr hWnd, int nIndex, IntPtr dwNewLong)
{
    int error = 0;
    IntPtr result = IntPtr.Zero;
    // Win32 SetWindowLong doesn't clear error on success
    SetLastError(0);

    if (IntPtr.Size == 4)
    {
        // use SetWindowLong
        Int32 tempResult = IntSetWindowLong(hWnd, nIndex, IntPtrToInt32(dwNewLong));
        error = Marshal.GetLastWin32Error();
        result = new IntPtr(tempResult);
    }
    else
    {
        // use SetWindowLongPtr
        result = IntSetWindowLongPtr(hWnd, nIndex, dwNewLong);
        error = Marshal.GetLastWin32Error();
    }

    if ((result == IntPtr.Zero) && (error != 0))
    {
        throw new System.ComponentModel.Win32Exception(error);
    }

    return result;
}

[DllImport("user32.dll", EntryPoint = "SetWindowLongPtr", SetLastError = true)]
private static extern IntPtr IntSetWindowLongPtr(IntPtr hWnd, int nIndex, IntPtr dwNewLong);

[DllImport("user32.dll", EntryPoint = "SetWindowLong", SetLastError = true)]
private static extern Int32 IntSetWindowLong(IntPtr hWnd, int nIndex, Int32 dwNewLong);

private static int IntPtrToInt32(IntPtr intPtr)
{
    return unchecked((int)intPtr.ToInt64());
}

[DllImport("kernel32.dll", EntryPoint = "SetLastError")]
public static extern void SetLastError(int dwErrorCode);
#endregion

Answer 2

I'm the author of H.NotifyIcon and I recently added extensions for the Window type - ShowInTaskbar and HideInTaskbar You can use them to achieve the desired behavior.

I think you just needed to write about it in issues on GitHub