Seamless Mode

[rom]

Hallo,
I am using SOAP API to control VirtualBox.
When I start VirtualBox process I would like to see its GUI.

I am using the following code:

var sessionGuid = _vboxService.IWebsessionManager_getSessionObject(_webServiceGuid);
consoleGuid = _vboxService.ISession_getConsole(sessionGuid);
var guestGuid = _vboxService.IConsole_getGuest(consoleGuid);

AdditionsFacilityStatus additionsFacilityStatus;
_vboxService.IGuest_getFacilityStatus(guestGuid, AdditionsFacilityType.Seamless, out additionsFacilityStatus);

while(additionsFacilityStatus!=AdditionsFacilityStatus.Active)
{
Thread.Sleep(100);
_vboxService.IGuest_getFacilityStatus(guestGuid, AdditionsFacilityType.Seamless, out additionsFacilityStatus);
}

var displayGuid=_vboxService.IConsole_getDisplay(consoleGuid);
_vboxService.IDisplay_setSeamlessMode(displayGuid, true);
_vboxService.IDisplay_invalidateAndUpdate(displayGuid);

Howereve I see no GUI.
How to correct it?

Thanks