Prevent Computer Sleep in C#

PreventSleep.cs

internal static class NativeMethods {

        public static void PreventSleep() {
            SetThreadExecutionState(ExecutionState.EsContinuous | ExecutionState.EsSystemRequired);
        }

        public static void AllowSleep() {
            SetThreadExecutionState(ExecutionState.EsContinuous);
        }

        [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern ExecutionState SetThreadExecutionState(ExecutionState esFlags);

        [FlagsAttribute]
        private enum ExecutionState : uint {
            EsAwaymodeRequired = 0x00000040,
            EsContinuous = 0x80000000,
            EsDisplayRequired = 0x00000002,
            EsSystemRequired = 0x00000001
        }
    }

This does not work. Is the call to PreventSleep should be periodic?
I wired it the PreventSleep and AllowSleep to buttons - tried it out but does not work...

In my program, it works if you don't press the 'Power saving button' in Windows. & you don't have to call PreventSleep periodically

I got this to work, after spinning a thread and calling the PreventSleep() every minute. Thank you and awesome work!