Enable secondary monitor programmatically

Question

I want to be able to enable my secondary monitor with C# in Windows Vista. Here is what I do:

SafeNativeMethods.EnumDisplayDevices(null, (uint)id, ref d, (uint)0);
...
SafeNativeMethods.EnumDisplaySettings(d.DeviceName, -2, ref mode0);
...
SafeNativeMethods.DEVMODE dm = mode0;

dm.dmPosition.x = 1440;
dm.dmFields = SafeNativeMethods.DM_POSITION;
long result = SafeNativeMethods.ChangeDisplaySettingsEx(d.DeviceName, ref dm, IntPtr.Zero, SafeNativeMethods.CDS_NORESET| SafeNativeMethods.CDS_UPDATEREGISTRY, IntPtr.Zero);
result = SafeNativeMethods.ChangeDisplaySettingsEx(null, ref dm, IntPtr.Zero, SafeNativeMethods.CDS_UPDATEREGISTRY, IntPtr.Zero);

This does not affect my secondary monitor even if I get 0 as result (which means SUCCESSFUL).

What have I done wrong ?

Thank you.

Answer 1

I haven't tried it myself, but it seems the folks over at this forum have a clue. The code is not C#, but it's understandable.

Answer 2

I think you need to set more than just the Position field, you could probably get the current settings from EnumDisplaySettings (at least the size and color, maybe refresh rate also)