Windows Form maximized overall absolutely

Question

I have a question to put my window in front of all absolutely, but when I launch a print dialog I cant found anyway to hold my window in front: I got to hold my window over the print dialog doing the TopMost, but the taskbar appears although is hidden.

The code in my form window to maximize it and put it overall:

this.StartPosition = System.Windows.Forms.FormStartPosition.Manual;
this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
this.WindowState = System.Windows.Forms.FormWindowState.Maximized;
this.TopMost = true;

The code that launch the print dialog:

PrinterSettings printerSettings = new PrinterSettings();
IntPtr hDevMode = printerSettings.GetHdevmode(printerSettings.DefaultPageSettings);
IntPtr pDevMode = GlobalLock(hDevMode);
int sizeNeeded = DocumentProperties(IntPtr.Zero, IntPtr.Zero, printerSettings.PrinterName, IntPtr.Zero, pDevMode, 0);
IntPtr devModeData = Marshal.AllocHGlobal(sizeNeeded);

DocumentProperties(IntPtr.Zero, IntPtr.Zero, printerSettings.PrinterName, devModeData, pDevMode, 14);
// <--- Here the print dialog appears and the thread stops till I close the dialog

GlobalUnlock(hDevMode);
printerSettings.SetHdevmode(devModeData);
printerSettings.DefaultPageSettings.SetHdevmode(devModeData);
GlobalFree(hDevMode);
Marshal.FreeHGlobal(devModeData);

Here the code where I hide the taskbar:

public class Taskbar
{
    [System.Runtime.InteropServices.DllImport("user32.dll")]
    private static extern int FindWindow(string className, string windowText);

    [System.Runtime.InteropServices.DllImport("user32.dll")]
    private static extern int ShowWindow(int hwnd, int command);

    private const int SW_HIDE = 0;
    private const int SW_SHOW = 1;

    public Taskbar()
    {
    }

    protected static int Handle
    {
        get
        {
            return FindWindow("Shell_TrayWnd", "");
        }
    }

    public static void Show()
    {
        ShowWindow(Handle, SW_SHOW);
    }

    public static void Hide()
    {
        ShowWindow(Handle, SW_HIDE);
    }
}

I tried this code also calling SetWinFullScreen in my form after "this.TopMost = true;" to maximize the form but it doesn't work either:

public class WinApi
{
    [DllImport("user32.dll", EntryPoint = "GetSystemMetrics")]
    private static extern int GetSystemMetrics(int which);

    [DllImport("user32.dll")]
    private static extern void
        SetWindowPos(IntPtr hwnd, IntPtr hwndInsertAfter,
                     int X, int Y, int width, int height, uint flags);        

    private const int SM_CXSCREEN = 0;
    private const int SM_CYSCREEN = 1;
    private static IntPtr HWND_TOP = IntPtr.Zero;
    private const int SWP_SHOWWINDOW = 64; // 0×0040

    public static int ScreenX
    {
        get { return GetSystemMetrics(SM_CXSCREEN);}
    }

    public static int ScreenY
    {
        get { return GetSystemMetrics(SM_CYSCREEN);}
    }

    public static void SetWinFullScreen(IntPtr hwnd)
    {
        SetWindowPos(hwnd, HWND_TOP, 0, 0, ScreenX, ScreenY, SWP_SHOWWINDOW);
    }
}

In all cases, when the print dialog is launched, the taskbar appears and the user can click it because is it in front of everything.

Is there a way to launch this print dialog in the background or put my form topmost absolutely (without any taskbar or dialog appearing) ?

Edited: The problem is in this line:

DocumentProperties(IntPtr.Zero, IntPtr.Zero, printerSettings.PrinterName, devModeData, pDevMode, 14);

This line launch the print dialog and then taskbar appears (hide or not).

Answer 1

A print dialog is not a form, it is a control that inherits from form, like textbox and combobox. So you shouldn't expect topmost to apply. The emphasis below is mine.

A topmost form is a form that overlaps all the other (non-topmost) forms even if it is not the active or foreground form. Topmost forms are always displayed at the highest point in the z-order of the windows on the desktop. You can use this property to create a form that is always displayed in your application, such as a Find and Replace tool window.

http://msdn.microsoft.com/en-us/library/system.windows.forms.form.topmost.aspx

Answer 2

This link was useful to get near solution to the problem: Hide Start Orb on Vista / Win 7 in C#

Following the steps of the link, I Adding to my Taskbar class:

[System.Runtime.InteropServices.DllImport("user32.dll")]
private static extern IntPtr FindWindowEx(
           IntPtr parentHwnd,
           IntPtr childAfterHwnd,
           IntPtr className,
           string windowText);

public static void Show()
{
        ShowWindow(Handle, SW_SHOW);
        ShowWindow(FindWindowEx(IntPtr.Zero, IntPtr.Zero, (IntPtr)0xC017, null), SW_SHOW);
}

public static void Hide()
{
        ShowWindow(Handle, SW_HIDE);
        ShowWindow(FindWindowEx(IntPtr.Zero, IntPtr.Zero, (IntPtr)0xC017, null), SW_HIDE);
}

And using the TopMost. Then when the dialog box appears I control the moment and focus my application fastly to put in front of the 'popup' but this time no show taskbar/windows icon and the user cant click nothing.

Is not the perfect solution but it is valid for me.