使用WinPcap（Windows Packet Capture）庫可以實現在C#中進行流量分析。以下是一個簡單的示例代碼，用于捕獲網絡流量并分析其中的數據包：

using System;
using System.Threading;
using PcapDotNet.Core;
using PcapDotNet.Packets;

class Program
{
    static void Main(string[] args)
    {
        // Retrieve the device list
        IList<LivePacketDevice> allDevices = LivePacketDevice.AllLocalMachine;

        if (allDevices.Count == 0)
        {
            Console.WriteLine("No interfaces found! Make sure WinPcap is installed.");
            return;
        }

        // Select the device for capture
        LivePacketDevice selectedDevice = allDevices[0];

        // Open the device
        using (PacketCommunicator communicator = selectedDevice.Open(65536, PacketDeviceOpenAttributes.Promiscuous, 1000))
        {
            // Start the capture loop
            communicator.ReceivePackets(0, PacketHandler);
        }
    }

    private static void PacketHandler(Packet packet)
    {
        // Print packet information
        Console.WriteLine(packet.Timestamp.ToString("yyyy-MM-dd HH:mm:ss.fff") + " length:" + packet.Length);
        
        // Parse the packet
        EthernetDatagram ethernet = packet.Ethernet;
        if (ethernet.EtherType == EthernetType.IpV4)
        {
            IpV4Datagram ip = ethernet.IpV4;
            Console.WriteLine("Source IP: " + ip.Source + " Destination IP: " + ip.Destination);
        }
        else if (ethernet.EtherType == EthernetType.Arp)
        {
            ArpDatagram arp = ethernet.Arp;
            Console.WriteLine("ARP: Sender IP: " + arp.SenderProtocolIpV4Address + " Target IP: " + arp.TargetProtocolIpV4Address);
        }
    }
}

在上面的示例中，我們首先獲取本地機器上的所有網絡設備列表，然后選擇第一個設備進行網絡流量捕獲。隨后，通過打開所選設備并設置捕獲參數，我們可以使用ReceivePackets()方法來開始捕獲網絡數據包。在PacketHandler方法中，我們可以對捕獲到的數據包進行分析和處理。