using System;
using System.Runtime.InteropServices;

namespace ConsoleApp1
{
    public class Class1
    {
        static void Main(string[] args)
        {
            Console.WriteLine("总内存：" + FormatSize(GetTotalPhys()));
            Console.WriteLine("已使用：" + FormatSize(GetUsedPhys()));
            Console.WriteLine("可使用：" + FormatSize(GetAvailPhys()));
            Console.ReadKey();
        }

        #region 获得内存信息API
        [DllImport("kernel32.dll")]
        [return: MarshalAs(UnmanagedType.Bool)]
        public static extern bool GlobalMemoryStatusEx(ref MEMORY_INFO mi);

        //定义内存的信息结构
        [StructLayout(LayoutKind.Sequential)]
        public struct MEMORY_INFO
        {
            public uint dwLength; //当前结构体大小
            public uint dwMemoryLoad; //当前内存使用率
            public ulong ullTotalPhys; //总计物理内存大小
            public ulong ullAvailPhys; //可用物理内存大小
            public ulong ullTotalPageFile; //总计交换文件大小
            public ulong ullAvailPageFile; //总计交换文件大小
            public ulong ullTotalVirtual; //总计虚拟内存大小
            public ulong ullAvailVirtual; //可用虚拟内存大小
            public ulong ullAvailExtendedVirtual; //保留 这个值始终为0
        }
        #endregion

        #region 格式化容量大小
        /// <summary>
        /// 格式化容量大小
        /// </summary>
        /// <param name="size">容量（B）</param>
        /// <returns>已格式化的容量</returns>
        private static string FormatSize(double size)
        {
            double d = (double)size;
            int i = 0;
            while ((d > 1024) && (i < 5))
            {
                d /= 1024;
                i++;
            }
            string[] unit = { "B", "KB", "MB", "GB", "TB" };
            return (string.Format("{0} {1}", Math.Round(d, 2), unit[i]));
        }
        #endregion

        #region 获得当前内存使用情况
        /// <summary>
        /// 获得当前内存使用情况
        /// </summary>
        /// <returns></returns>
        public static MEMORY_INFO GetMemoryStatus()
        {
            MEMORY_INFO mi = new MEMORY_INFO();
            mi.dwLength = (uint)System.Runtime.InteropServices.Marshal.SizeOf(mi);
            GlobalMemoryStatusEx(ref mi);
            return mi;
        }
        #endregion

        #region 获得当前可用物理内存大小
        /// <summary>
        /// 获得当前可用物理内存大小
        /// </summary>
        /// <returns>当前可用物理内存（B）</returns>
        public static ulong GetAvailPhys()
        {
            MEMORY_INFO mi = GetMemoryStatus();
            return mi.ullAvailPhys;
        }
        #endregion

        #region 获得当前已使用的内存大小
        /// <summary>
        /// 获得当前已使用的内存大小
        /// </summary>
        /// <returns>已使用的内存大小（B）</returns>
        public static ulong GetUsedPhys()
        {
            MEMORY_INFO mi = GetMemoryStatus();
            return (mi.ullTotalPhys - mi.ullAvailPhys);
        }
        #endregion

        #region 获得当前总计物理内存大小
        /// <summary>
        /// 获得当前总计物理内存大小
        /// </summary>
        /// <returns&amp;gt;总计物理内存大小（B）&amp;lt;/returns&amp;gt;
        public static ulong GetTotalPhys()
        {
            MEMORY_INFO mi = GetMemoryStatus();
            return mi.ullTotalPhys;
        }
        #endregion
    }
}

using System;
using System.Management;

namespace ConsoleApp1
{
    public class Class1
    {
        static void Main(string[] args)
        {
            //需要添加 System.Management 的引用


            //获取总物理内存大小
            ManagementClass cimobject1 = new ManagementClass("Win32_PhysicalMemory");
            ManagementObjectCollection moc1 = cimobject1.GetInstances();
            double available=0, capacity=0;
            foreach (ManagementObject mo1 in moc1)
            {
                capacity += ((Math.Round(Int64.Parse(mo1.Properties["Capacity"].Value.ToString()) / 1024 / 1024 / 1024.0, 1)));
            }
            moc1.Dispose();
            cimobject1.Dispose();


            //获取内存可用大小
            ManagementClass cimobject2 = new ManagementClass("Win32_PerfFormattedData_PerfOS_Memory");
            ManagementObjectCollection moc2 = cimobject2.GetInstances();
            foreach (ManagementObject mo2 in moc2)
            {
                available += ((Math.Round(Int64.Parse(mo2.Properties["AvailableMBytes"].Value.ToString()) / 1024.0, 1)));

            }
            moc2.Dispose();
            cimobject2.Dispose();

            Console.WriteLine("总内存=" + capacity.ToString() + "G");
            Console.WriteLine("可使用=" + available.ToString() + "G");
            Console.WriteLine("已使用=" + ((capacity - available)).ToString() + "G," + (Math.Round((capacity - available) / capacity * 100, 0)).ToString() + "%");
            Console.ReadKey();
        }
    }
}

using System;
using System.Diagnostics;

namespace ConsoleApp1
{
    public class Class1
    {
        static void Main(string[] args)
        {
            PerformanceCounter cpuCounter;
            PerformanceCounter ramCounter;

            cpuCounter = new PerformanceCounter();
            cpuCounter.CategoryName = "Processor";
            cpuCounter.CounterName = "% Processor Time";
            cpuCounter.InstanceName = "_Total";
            cpuCounter = new PerformanceCounter("Processor", "% Processor Time", "_Total");
            ramCounter = new PerformanceCounter("Memory", "Available MBytes");



            Console.WriteLine("电脑CPU使用率：" + cpuCounter.NextValue() + "%");
            Console.WriteLine("电脑可使用内存：" + ramCounter.NextValue() + "MB");
            Console.WriteLine();



            while (true)
            {
                System.Threading.Thread.Sleep(1000);
                Console.WriteLine("电脑CPU使用率：" + cpuCounter.NextValue() + " %");
                Console.WriteLine("电脑可使用内存：" + ramCounter.NextValue() + "MB");
                Console.WriteLine();

                if ((int)cpuCounter.NextValue() > 80)
                {
                    System.Threading.Thread.Sleep(1000 * 60);
                }
            }
        }
    }
}