Can't change DEVMODE of a printer

I need to change DEVMODE of printer for current printing task to pass standard and device-specific settings. I do the following:

    PrintDocument d =newPrintDocument();
    d.PrinterSettings.PrinterName="Microsoft XPS Document Writer"; // example printer name           
    byte[] devmode_data;// contains a valid value that is obtained from registry
    IntPtr devmode =IntPtr.Zero;
    GCHandle handle =GCHandle.Alloc(devmode_data,GCHandleType.Pinned);
    try
    {
        devmode = handle.AddrOfPinnedObject();
        if(devmode !=IntPtr.Zero) d.PrinterSettings.SetHdevmode(devmode);
    }
    finally
    {
        if(handle.IsAllocated) handle.Free();
    }    

It fails when I attempt to execute PrinterSettings.SetHdevmode with a NullReferenceException and without any meaningful error info. d.PrinterSettings is not null, the exception is thrown inside of PrinterSettings.SetHdevmode method. So my question is: what is wrong? Is the byte[] to IntPtr cast is wrong? Maybe SetHdevmode expects something other than byte[] array?

I get the byte[] devmode_data array from the registry. It is a valid value and it is same value that is used in current printer settings.