前言：本文介绍为什么使用Dns.GetHostAddresses()在不同计算机上执行结果不同的原因；并且给出了筛选IPv4或者ipv6地址的代码。
在XPsp3系统和Win7系统分别执行Dns.GetHostAddresses()方法，得到了不同的结果：
win7：
xp：
xp中在cmd输入如下命令：
原因可知：xpsp3系统没有安装ipv6协议，下面安装进行测试：
安装ipv6协议：
再输入ipv6 if >D:ipv6if.txt
输出内容如下：
Interface 6: Ethernet: 本地连接 Guid {14F445CB-3489-474B-B644-5F749E251F46} uses Neighbor Discovery uses Router Discovery link-layer address: b8-ac-6f-c6-09-79 preferred link-local fe80::baac:6fff:fec6:979, life infinite multicast interface-local ff01::1, 1 refs, not reportable multicast link-local ff02::1, 1 refs, not reportable multicast link-local ff02::1:ffc6:979, 1 refs, last reporter link MTU 1500 (true link MTU 1500) current hop limit 128 reachable time 15500ms (base 30000ms) retransmission interval 1000ms DAD transmits 1 default site prefix length 48 Interface 5: Ethernet: 无线网络连接 Guid {198A6F64-4D3D-47EC-A720-9579E2A3EBDE} zones: link 5 site 2 cable unplugged uses Neighbor Discovery uses Router Discovery link-layer address: ec-55-f9-44-dc-c0 tentative link-local fe80::ee55:f9ff:fe44:dcc0, life infinite multicast interface-local ff01::1, 1 refs, not reportable multicast link-local ff02::1, 1 refs, not reportable multicast link-local ff02::1:ff44:dcc0, 1 refs, last reporter link MTU 1500 (true link MTU 1500) current hop limit 128 reachable time 44000ms (base 30000ms) retransmission interval 1000ms DAD transmits 1 default site prefix length 48 Interface 4: Teredo Tunneling Pseudo-Interface Guid {7F6865DC-7663-4482-BD9E-D689A49C1C3A} zones: link 4 site 3 cable unplugged uses Neighbor Discovery uses Router Discovery routing preference 2 link-layer address: 0.0.0.0:0 preferred link-local fe80::ffff:ffff:fffd, life infinite multicast interface-local ff01::1, 1 refs, not reportable multicast link-local ff02::1, 1 refs, not reportable link MTU 1280 (true link MTU 1280) current hop limit 128 reachable time 27000ms (base 30000ms) retransmission interval 1000ms DAD transmits 0 default site prefix length 48 Interface 3: 6to4 Tunneling Pseudo-Interface Guid {A995346E-9F3E-2EDB-47D1-9CC7BA01CD73} does not use Neighbor Discovery does not use Router Discovery routing preference 1 link MTU 1280 (true link MTU 65515) current hop limit 128 reachable time 29000ms (base 30000ms) retransmission interval 1000ms DAD transmits 0 default site prefix length 48 Interface 2: Automatic Tunneling Pseudo-Interface Guid {48FCE3FC-EC30-E50E-F1A7-71172AEEE3AE} does not use Neighbor Discovery does not use Router Discovery routing preference 1 EUI-64 embedded IPv4 address: 0.0.0.0 router link-layer address: 0.0.0.0 preferred link-local fe80::5efe:192.168.0.60, life infinite link MTU 1280 (true link MTU 65515) current hop limit 128 reachable time 41500ms (base 30000ms) retransmission interval 1000ms DAD transmits 0 default site prefix length 48 Interface 1: Loopback Pseudo-Interface Guid {6BD113CC-5EC2-7638-B953-0B889DA72014} zones: link 1 site 4 does not use Neighbor Discovery does not use Router Discovery link-layer address: preferred link-local ::1, life infinite preferred link-local fe80::1, life infinite link MTU 1500 (true link MTU 4294967295) current hop limit 128 reachable time 44000ms (base 30000ms) retransmission interval 1000ms DAD transmits 0 default site prefix length 48
重新运行xp系统程序：
可以使用下面代码过滤，取得ipv4地址或者ipv6地址：
IPAddress address1 = Dns.GetHostAddresses(Dns.GetHostName()).Where(ip => ip.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork).First();
IPAddress address2 = Dns.GetHostAddresses(Dns.GetHostName()).Where(ip => ip.AddressFamily == System.Net.Sockets.AddressFamily.InterNetworkV6).First();