说明：  Visual C#自动更新本机IP地址，首先判断网络连接是否可用，然后设置ip地址和子网掩码、设置和获取网关地址、设置DNS、显示本地连接信息、获取IP地址、获取子网掩码、获取默认网关、获取DNS服务器、显示子网掩码、显示默认网关、显示DNS服务器等，新手可以学习到上述技巧。
(Visual C# automatically update the IP address of the machine, first determine whether the network connection is available, and then set the IP address and subnet mask set and get the gateway address, set the DNS local connection information, obtain an IP address, subnet mask, Get default gateway, obtain the DNS server Displays the subnet mask, default gateway is displayed, showing the DNS server, the novice can learn the skills.)