C# 呼叫 IpHlpApi 取得網路介面卡資訊與流量統計

編輯：關於C語言

使用 GetIfTable API 監控網路流量

.NET Framework 未直接提供取得網卡即時流量的類別，可透過 P/Invoke 呼叫 IpHlpApi.dll 的 GetIfTable 函式，取得 MIB_IF_TABLE 結構，包含每張網卡的位元組收發計數、速度、類型、MAC 位址等資訊。

API 定義與結構對應

using System;
using System.Runtime.InteropServices;
using System.Collections.Generic;
using System.Text;

public class NetworkMonitor
{
    [DllImport("IpHlpApi.dll", SetLastError = true)]
    private static extern uint GetIfTable(byte[] pIfTable, ref uint pdwSize, bool bOrder);

    // 對應 MIB_IFROW 結構
    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
    private struct MIB_IFROW
    {
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
        public string wszName;
        public uint dwIndex;
        public uint dwType;
        public uint dwMtu;
        public uint dwSpeed;
        public uint dwPhysAddrLen;
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 8)]
        public byte[] bPhysAddr;
        public uint dwAdminStatus;
        public uint dwOperStatus;
        public uint dwLastChange;
        public uint dwInOctets;
        public uint dwInUcastPkts;
        public uint dwInNUcastPkts;
        public uint dwInDiscards;
        public uint dwInErrors;
        public uint dwInUnknownProtos;
        public uint dwOutOctets;
        public uint dwOutUcastPkts;
        public uint dwOutNUcastPkts;
        public uint dwOutDiscards;
        public uint dwOutErrors;
        public uint dwOutQLen;
        public uint dwDescrLen;
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 256)]
        public byte[] bDescr;
    }

    // 對應 MIB_IFTABLE 結構
    [StructLayout(LayoutKind.Sequential)]
    private struct MIB_IFTABLE
    {
        public uint dwNumEntries;
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 1)] // 實際大小由 dwNumEntries 決定
        public MIB_IFROW[] table;
    }
}

取得所有網卡資訊

public class NetInfo
{
    public string Name { get; set; }
    public string Description { get; set; }
    public string MacAddress { get; set; }
    public uint Speed { get; set; } // bps
    public uint InBytes { get; set; }
    public uint OutBytes { get; set; }
    public OperationalStatus Status { get; set; }
}

public static List GetAllNetworkInfo()
{
    List list = new List();

    // 先取得緩衝區大小
    uint size = 0;
    uint ret = GetIfTable(null, ref size, false);
    if (ret != 122) // ERROR_INSUFFICIENT_BUFFER
        throw new System.ComponentModel.Win32Exception((int)ret);

    byte[] buffer = new byte[size];
    ret = GetIfTable(buffer, ref size, false);
    if (ret != 0)
        throw new System.ComponentModel.Win32Exception((int)ret);

    // 將 byte[] 反序列化為結構
    GCHandle handle = GCHandle.Alloc(buffer, GCHandleType.Pinned);
    try
    {
        IntPtr ptr = handle.AddrOfPinnedObject();
        MIB_IFTABLE table = (MIB_IFTABLE)Marshal.PtrToStructure(ptr, typeof(MIB_IFTABLE));

        // 重新計算陣列實際大小
        int rowSize = Marshal.SizeOf(typeof(MIB_IFROW));
        table.table = new MIB_IFROW[table.dwNumEntries];
        IntPtr rowPtr = new IntPtr(ptr.ToInt64() + Marshal.SizeOf(typeof(uint))); // 跳過 dwNumEntries

        for (int i = 0; i < table.dwNumEntries; i++)
        {
            MIB_IFROW row = (MIB_IFROW)Marshal.PtrToStructure(rowPtr, typeof(MIB_IFROW));
            table.table[i] = row;
            rowPtr = new IntPtr(rowPtr.ToInt64() + rowSize);
        }

        // 轉換為友善模型
        foreach (var row in table.table)
        {
            list.Add(new NetInfo
            {
                Name = Encoding.ASCII.GetString(row.wszName).TrimEnd('\0'),
                Description = Encoding.ASCII.GetString(row.bDescr, 0, (int)row.dwDescrLen).TrimEnd('\0'),
                MacAddress = BitConverter.ToString(row.bPhysAddr, 0, (int)row.dwPhysAddrLen).Replace('-', ':'),
                Speed = row.dwSpeed,
                InBytes = row.dwInOctets,
                OutBytes = row.dwOutOctets,
                Status = (OperationalStatus)row.dwOperStatus
            });
        }
    }
    finally
    {
        handle.Free();
    }
    return list;
}

使用範例：即時顯示下載/上傳速度

var prev = GetAllNetworkInfo();
while (true)
{
    Thread.Sleep(1000);
    var curr = GetAllNetworkInfo();
    for (int i = 0; i < curr.Count; i++)
    {
        if (curr[i].Name == prev[i].Name)
        {
            double downKB = (curr[i].InBytes - prev[i].InBytes) / 1024.0;
            double upKB = (curr[i].OutBytes - prev[i].OutBytes) / 1024.0;
            Console.WriteLine($"{curr[i].Description} ↓{downKB:F1} KB/s ↑{upKB:F1} KB/s");
        }
    }
    prev = curr;
}