SystemInfoHelper

SystemInfoHelper.cs

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Management;

public static class SystemInfoHelper
{
    // Stores last CPU samples per PID (important if pool recycles)
    private static readonly ConcurrentDictionary<int, TimeSpan> _lastCpu =
        new ConcurrentDictionary<int, TimeSpan>();

    private static readonly ConcurrentDictionary<int, DateTime> _lastSampleTime =
        new ConcurrentDictionary<int, DateTime>();

    /// <summary>
    /// Returns the CPU usage percentage of an IIS App Pool worker process.
    /// Does NOT require PerformanceCounter or registry access.
    /// </summary>
    public static double GetCpuUsage(string appPoolName)
    {
        var process = GetProcessByAppPool(appPoolName);
        var pid = process.Id;

        var now = DateTime.UtcNow;
        var currentCpu = process.TotalProcessorTime;

        var lastCpu = _lastCpu.GetOrAdd(pid, TimeSpan.Zero);
        var lastTime = _lastSampleTime.GetOrAdd(pid, now);

        var cpuUsedMs = (currentCpu - lastCpu).TotalMilliseconds;
        var elapsedMs = (now - lastTime).TotalMilliseconds;

        _lastCpu[pid] = currentCpu;
        _lastSampleTime[pid] = now;

        if (elapsedMs <= 0)
            return 0;

        var cpuPercent = cpuUsedMs / (elapsedMs * Environment.ProcessorCount);
        cpuPercent = Math.Max(0, Math.Min(cpuPercent, 1));

        return Math.Round(cpuPercent * 100, 2);
    }

    /// <summary>
    /// Returns the memory usage (Working Set) of an IIS App Pool worker process in MB.
    /// </summary>
    public static double GetMemoryUsageMB(string appPoolName)
    {
        var process = GetProcessByAppPool(appPoolName);
        var bytes = process.WorkingSet64;

        return Math.Round(bytes / 1024.0 / 1024.0, 2);
    }

    /// <summary>
    /// Returns readable uptime text for an IIS App Pool worker process.
    /// </summary>
    public static string GetReadableUptime(string appPoolName)
    {
        var process = GetProcessByAppPool(appPoolName);
        var uptime = DateTime.UtcNow - process.StartTime.ToUniversalTime();

        return TimeSpanToReadableString(uptime);
    }

    /// <summary>
    /// Resolves the w3wp.exe process associated with an IIS App Pool.
    /// </summary>
private static Process GetProcessByAppPool(string appPoolName)
{
    using var searcher = new ManagementObjectSearcher(
        "SELECT ProcessId, CommandLine FROM Win32_Process WHERE Name='w3wp.exe'");

    foreach (ManagementObject obj in searcher.Get())
    {
        var cmd = obj["CommandLine"]?.ToString();
        if (string.IsNullOrWhiteSpace(cmd))
            continue;

        if (cmd.IndexOf("-ap", StringComparison.OrdinalIgnoreCase) >= 0 &&
            cmd.IndexOf(appPoolName, StringComparison.OrdinalIgnoreCase) >= 0)
        {
            var pid = Convert.ToInt32(obj["ProcessId"]);
            return Process.GetProcessById(pid);
        }
    }

    throw new InvalidOperationException(
        $"App Pool '{appPoolName}' not found. Ensure the pool is running and received traffic.");
}

    /// <summary>
    /// Converts a TimeSpan to a friendly human-readable string.
    /// </summary>
    private static string TimeSpanToReadableString(TimeSpan ts)
    {
        var parts = new List<string>();

        if (ts.Days > 0)
            parts.Add($"{ts.Days} day{(ts.Days > 1 ? "s" : "")}");

        if (ts.Hours > 0)
            parts.Add($"{ts.Hours} hour{(ts.Hours > 1 ? "s" : "")}");

        if (ts.Minutes > 0)
            parts.Add($"{ts.Minutes} minute{(ts.Minutes > 1 ? "s" : "")}");

        if (ts.Seconds > 0)
            parts.Add($"{ts.Seconds} second{(ts.Seconds > 1 ? "s" : "")}");

        return parts.Count == 0 ? "0 seconds" : string.Join(", ", parts);
    }
}