[WPF]WindowStyle が None なウィンドウを ALT+TAB で表示させないようにする

gistfile1.cs

public class Native
{
    [Flags]
    public enum ExtendedWindowStyles
    {
        WS_EX_TOOLWINDOW = 0x80
    }

    public enum GetWindowLongFields
    {
        GWL_EXSTYLE = -20
    }

    #region GetWindowLontPtr

    [DllImport("user32.dll", EntryPoint = "GetWindowLong")]
    private static extern IntPtr GetWindowLongPtr32(IntPtr hWnd, int nIndex);

    [DllImport("user32.dll", EntryPoint = "GetWindowLongPtr")]
    private static extern IntPtr GetWindowLongPtr64(IntPtr hWnd, int nIndex);

    public static IntPtr GetWindowLontPtr(IntPtr hWnd, int nIndex)
    {
        return IntPtr.Size == 8 ? GetWindowLongPtr64(hWnd, nIndex) : GetWindowLongPtr32(hWnd, nIndex);
    }

    #endregion

    #region SetWindowLongPtr

    [DllImport("user32.dll", EntryPoint = "SetWindowLong")]
    private static extern int SetWindowLong32(IntPtr hWnd, int nIndex, int dwNewLong);

    [DllImport("user32.dll", EntryPoint = "SetWindowLongPtr")]
    private static extern IntPtr SetWindowLongPtr64(IntPtr hWnd, int nIndex, IntPtr dwNewLong);

    public static IntPtr SetWindowLongPtr(IntPtr hWnd, int nIndex, IntPtr dwNewLong)
    {
        return IntPtr.Size == 8 ? SetWindowLongPtr64(hWnd, nIndex, dwNewLong)
            : new IntPtr(SetWindowLong32(hWnd, nIndex, dwNewLong.ToInt32()));
    }

    #endregion
}


public partial class DummyWindow : Window
{
    public DummyWindow()
    {
        InitializeComponent();
    }

    private void Window_SourceInitialized(object sender, EventArgs e)
    {
        var helper = new WindowInteropHelper(this);
        var exStyle = Native.GetWindowLontPtr(helper.Handle, (int)Native.GetWindowLongFields.GWL_EXSTYLE).ToInt32();
        exStyle = exStyle | (int)Native.ExtendedWindowStyles.WS_EX_TOOLWINDOW;
        Native.SetWindowLongPtr(helper.Handle, (int)Native.GetWindowLongFields.GWL_EXSTYLE, new IntPtr(exStyle));
    }
}