.Net获取IP地址的方法

  /// <summary>    
  /// 获取ipv4地址    
  /// </summary>    
  /// <returns>
  </returns>  
  public static string getip4address(httprequest request = null)    
  {      
  func<ipaddress, bool> f = e => e.addressfamily.tostring() == "internetwork";      
  ipaddress ipa = dns.gethostaddresses((request
  ?? httpcontext.current.request).userhostaddress).firstordefault(f)        
  ?? dns.gethostaddresses(dns.gethostname()).firstordefault(f);      
  if (ipa != null)     
  {       
  return ipa.tostring();    
  }      
  return httpcontext.current.request.userhostaddress;   
  }