Why is SetThreadAffinityMask ignored?

Question

Why is SetThreadAffinityMask ignored? I'm trying to write a program that sets the Affinity of each process thread according to the value of IdealProcessor. But SetThreadAffinityMask is ignored.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Runtime.InteropServices;
using System.Diagnostics;

namespace ThreadAffinity
{
    class Program
    {
        [DllImport("kernel32.dll")]
        static extern IntPtr OpenThread(ThreadAccess dwDesiredAccess, bool bInheritHandle, uint dwThreadId);

        [DllImport("kernel32.dll")]
        static extern bool SetThreadAffinityMask(IntPtr hThread, IntPtr dwThreadAffinityMask);

        [DllImport("kernel32.dll")]
        static extern bool GetThreadIdealProcessorEx(IntPtr hThread, ref PROCESSOR_NUMBER lpIdealProcessor);

        [DllImport("kernel32.dll")]
        static extern bool CloseHandle(IntPtr hObject);

        [StructLayout(LayoutKind.Sequential)]
        public struct PROCESSOR_NUMBER
        {
            public ushort Group;
            public byte Number;
            public byte Reserved;
        }

        [Flags]
        public enum ThreadAccess : int
        {
            TERMINATE = (0x0001),
            SUSPEND_RESUME = (0x0002),
            GET_CONTEXT = (0x0008),
            SET_CONTEXT = (0x0010),
            SET_INFORMATION = (0x0020),
            QUERY_INFORMATION = (0x0040),
            SET_THREAD_TOKEN = (0x0080),
            IMPERSONATE = (0x0100),
            DIRECT_IMPERSONATION = (0x0200),
            THREAD_ALL_ACCESS = (0x1F03FF)
        }

        static void Main(string[] args)
        {
            Console.WriteLine("Enter process id:");
            int processId = Convert.ToInt32(Console.ReadLine());
            Process process = Process.GetProcessById(processId);
            foreach (ProcessThread thread in process.Threads)
            {
                IntPtr hThread = OpenThread(ThreadAccess.QUERY_INFORMATION, false, (uint)thread.Id);
                PROCESSOR_NUMBER processorNumber = new PROCESSOR_NUMBER();
                GetThreadIdealProcessorEx(hThread, ref processorNumber);
                Console.WriteLine("Thread {0} ideal processor is {1}", thread.Id, processorNumber.Number);
                SetThreadAffinityMask(hThread, (IntPtr)(1 << processorNumber.Number));
                CloseHandle(hThread);
            }
            Console.WriteLine("Press any key to exit...");
            Console.ReadKey();
        }
    }
}

I can't deny that with 99% probability I'm an idiot, that's why I came here to ask for your help.

upd1: The program properly detects idealprocessor, but doesn't set affinity to the thread.

Answer 1

As @RaymondChen said

Per documentation: This handle must have the THREAD_SET_INFORMATION or THREAD_SET_LIMITED_INFORMATION access right and the THREAD_QUERY_INFORMATION or THREAD_QUERY_LIMITED_INFORMATION access right.