C# 准确获取系统 CPU 使用率

1.  PerformanceCounter 注意：（32位下不是线程安全的）

public class ProcessorUsage
{
    const float sampleFrequencyMillis = 1000;

    protected object syncLock = new object();
    protected PerformanceCounter counter;
    protected float lastSample;
    protected DateTime lastSampleTime;

    /// <summary>
    ///
    /// </summary>
    public ProcessorUsage()
    {
        this.counter = new PerformanceCounter("Processor", "% Processor Time", "_Total", true);
    }

    /// <summary>
    ///
    /// </summary>
    /// <returns></returns>
    public float GetCurrentValue()
    {
        if ((DateTime.UtcNow - lastSampleTime).TotalMilliseconds > sampleFrequencyMillis)
        {
            lock (syncLock)
            {
                if ((DateTime.UtcNow - lastSampleTime).TotalMilliseconds > sampleFrequencyMillis)
                {
                    lastSample = counter.NextValue();
                    lastSampleTime = DateTime.UtcNow;
                }
            }
        }

        return lastSample;
    }
}

2.WMI

ManagementObjectSearcher searcher = new ManagementObjectSearcher("select * from Win32_PerfFormattedData_PerfOS_Processor");
            var cpuTimes = searcher.Get()
                .Cast<managementobject>()
                .Select(mo => new
                {
                    Name = mo["Name"],
                    Usage = mo["PercentProcessorTime"]
                }
                )
                .ToList();

var query = cpuTimes.Where(x => x.Name.ToString() == "_Total").Select(x => x.Usage);
var cpuUsage = query.SingleOrDefault();