程序代码：

private void OnNewPacket(PacketMonitor pm, Packet p)
        {
            // add the new packet to the list
            m_Packets.Add(p);
            m_PacketsSize += p.TotalLength;
            this.lvShowData.Items.Add(new ListViewItem(new string[] { p.Time.ToString(), p.Source,p.Destination,p.Protocol.ToString(), p.TotalLength.ToString() }));
            this.statusBar1.Text="总共收到数据包为:"+m_PacketsSize.ToString()+"个";
           
        }

        private void btnStop_Click(object sender, System.EventArgs e)
        {
          m_PacketMonitors.Stop();
        }

        private void btnReset_Click(object sender, System.EventArgs e)
        {
            this.lvShowData.Items.Clear();
            this.tbShowData.Text="";

        }

        

        private void lvShowData_DoubleClick(object sender, System.EventArgs e)
        {
       
            ListView l = (ListView)sender;
            if (l.SelectedItems.Count> 0)
            {
                Packet p=(Packet)m_Packets[l.SelectedItems[0].Index];
                this.tbShowData.Text=p.ToString();
            }
        }

        private void 作者_Click(object sender, System.EventArgs e)
        {
            MessageBox.Show("作者：岳国兵\nQQ:32151611");
        }

       
    }
}[local]1[/local]

最好给我修改好以后的答案，  3Q   

  Packet p=(Packet)m_Packets[l.SelectedItems[0].Index]; //看不出来吧，看一下你的l.SelectedItems[0].Index是否有超过m_Packets最大下标的可能！