用winform实现以下功能：查找局域网内所有IP，选中IP后，将此IP输出到textbox当中

您可以使用以下代码实现此功能：

private void btnSearch_Click(object sender, EventArgs e)
{
    string localIP = GetLocalIP();
    string[] ipParts = localIP.Split('.');
    string baseIP = ipParts[0] + "." + ipParts[1] + "." + ipParts[2] + ".";
    for (int i = 1; i <= 255; i++)
    {
        string ip = baseIP + i.ToString();
        Ping ping = new Ping();
        ping.PingCompleted += new PingCompletedEventHandler(ping_PingCompleted);
        ping.SendAsync(ip, 100, ip);
    }
}

private void ping_PingCompleted(object sender, PingCompletedEventArgs e)
{
    string ip = (string)e.UserState;
    if (e.Reply != null && e.Reply.Status == IPStatus.Success)
    {
        this.Invoke(new Action(() =>
        {
            txtIPs.AppendText(ip + Environment.NewLine);
        }));
    }
}

private string GetLocalIP()
{
    IPHostEntry host = Dns.GetHostEntry(Dns.GetHostName());
    foreach (IPAddress ip in host.AddressList)
    {
        if (ip.AddressFamily == AddressFamily.InterNetwork)
        {
            return ip.ToString();
        }
    }
    return "";
}

这段代码使用Ping命令来扫描局域网内的所有IP地址，并将成功响应的IP地址输出到一个文本框中。