asp.net通过指定IP地址得到当前的网络上的主机的域名

<%@ImportNameSpace="System.Net"%>
<scriptlanguage="C#"runat=server>
protectedvoiddoClick(ObjectSrc,EventArgsE){
IPHostEntryhostInfo=DNS.GetHostByAddr(txtIP.Text);
showmsg.Text=hostInfo.Hostname;
}
</script>
<asp:Labelrunat=serverid=showmsg/>
<formid=testFormrunat=server>
要查找的IP地址：<asp:TextBoxrunat=serverid=txtIP/><asp:Buttonrunat=serverid=doText="查找"onClick=doClick/>
</form>