asp.net Core 使用过滤器判断请求客户端是否为移动端,并实现PC端和移动端请求映射和自动跳转

很多时候我们做网站时单纯的用bootstrap等前端框架实现的前端自适应带给用户的体验并不太好，所以为了提高用户体验会专门针对pc端网页重新设计一套移动端网页，但是怎么才能做到在移动端访问pc页面的时候返回对应的移动端页面，而不是pc端页面呢？下面我们就简单的进行介绍。主要技术是asp.net core。

第一步：自定义一个校验请求客户端类型的过滤器。该过滤器要实现3个功能：1.能够校验请求客户端为移动端还是pc端；2.能够配置请求路径的映射，即当前请求的pc端的路径对应的移动端路径；3.能够配置请求参数的映射。过滤器的实现如下

  public class userclientfilter : attribute, iauthorizationfilter
    {
        /// <summary>
        /// 是否检测客户端类型
        /// </summary>
        public bool ischeckclient { get; set; } = false;
        /// <summary>
        /// 跳转路径
        /// </summary>
        public string redirectpath { get; set; }
        
        /// <summary>
        /// 参数映射,格式：id=id|lawyerid=lawyerid|
        /// </summary>
        public string paras { get; set; }

        //regex from http://detectmobilebrowsers.com/
        private static readonly regex b = new regex(@"(android|bb\d+|meego).+mobile|avantgo|bada\/|blackberry|blazer|compal|elaine|fennec|hiptop|iemobile|ip(hone|od)|iris|kindle|lge |maemo|midp|mmp|mobile.+firefox|netfront|opera m(ob|in)i|palm( os)?|phone|p(ixi|re)\/|plucker|pocket|psp|series(4|6)0|symbian|treo|up\.(browser|link)|vodafone|wap|windows ce|xda|xiino", regexoptions.ignorecase | regexoptions.multiline);
        private static readonly regex v = new regex(@"1207|6310|6590|3gso|4thp|50[1-6]i|770s|802s|a wa|abac|ac(er|oo|s\-)|ai(ko|rn)|al(av|ca|co)|amoi|an(ex|ny|yw)|aptu|ar(ch|go)|as(te|us)|attw|au(di|\-m|r |s )|avan|be(ck|ll|nq)|bi(lb|rd)|bl(ac|az)|br(e|v)w|bumb|bw\-(n|u)|c55\/|capi|ccwa|cdm\-|cell|chtm|cldc|cmd\-|co(mp|nd)|craw|da(it|ll|ng)|dbte|dc\-s|devi|dica|dmob|do(c|p)o|ds(12|\-d)|el(49|ai)|em(l2|ul)|er(ic|k0)|esl8|ez([4-7]0|os|wa|ze)|fetc|fly(\-|_)|g1 u|g560|gene|gf\-5|g\-mo|go(\.w|od)|gr(ad|un)|haie|hcit|hd\-(m|p|t)|hei\-|hi(pt|ta)|hp( i|ip)|hs\-c|ht(c(\-| |_|a|g|p|s|t)|tp)|hu(aw|tc)|i\-(20|go|ma)|i230|iac( |\-|\/)|ibro|idea|ig01|ikom|im1k|inno|ipaq|iris|ja(t|v)a|jbro|jemu|jigs|kddi|keji|kgt( |\/)|klon|kpt |kwc\-|kyo(c|k)|le(no|xi)|lg( g|\/(k|l|u)|50|54|\-[a-w])|libw|lynx|m1\-w|m3ga|m50\/|ma(te|ui|xo)|mc(01|21|ca)|m\-cr|me(rc|ri)|mi(o8|oa|ts)|mmef|mo(01|02|bi|de|do|t(\-| |o|v)|zz)|mt(50|p1|v )|mwbp|mywa|n10[0-2]|n20[2-3]|n30(0|2)|n50(0|2|5)|n7(0(0|1)|10)|ne((c|m)\-|on|tf|wf|wg|wt)|nok(6|i)|nzph|o2im|op(ti|wv)|oran|owg1|p800|pan(a|d|t)|pdxg|pg(13|\-([1-8]|c))|phil|pire|pl(ay|uc)|pn\-2|po(ck|rt|se)|prox|psio|pt\-g|qa\-a|qc(07|12|21|32|60|\-[2-7]|i\-)|qtek|r380|r600|raks|rim9|ro(ve|zo)|s55\/|sa(ge|ma|mm|ms|ny|va)|sc(01|h\-|oo|p\-)|sdk\/|se(c(\-|0|1)|47|mc|nd|ri)|sgh\-|shar|sie(\-|m)|sk\-0|sl(45|id)|sm(al|ar|b3|it|t5)|so(ft|ny)|sp(01|h\-|v\-|v )|sy(01|mb)|t2(18|50)|t6(00|10|18)|ta(gt|lk)|tcl\-|tdg\-|tel(i|m)|tim\-|t\-mo|to(pl|sh)|ts(70|m\-|m3|m5)|tx\-9|up(\.b|g1|si)|utst|v400|v750|veri|vi(rg|te)|vk(40|5[0-3]|\-v)|vm40|voda|vulc|vx(52|53|60|61|70|80|81|83|85|98)|w3c(\-| )|webc|whit|wi(g |nc|nw)|wmlb|wonu|x700|yas\-|your|zeto|zte\-", regexoptions.ignorecase | regexoptions.multiline);

        private bool ismobilebrowser(httprequest request)
        {
            var useragent = request.useragent();
            if ((b.ismatch(useragent) || v.ismatch(useragent.substring(0, 4))))
            {
                return true;
            }

            return false;
        }

        private string useragent(httprequest request)
        {
            return request.headers["user-agent"];
        }
        

        public void onauthorization(authorizationfiltercontext context)
        {
            if (ischeckclient && ismobilebrowser(context.httpcontext.request))
            {
                string requesturl = redirectpath;
                if (!paras.isnull() && !context.httpcontext.request.querystring.value.isnull())
                {
                    var pramsetp = paras.split("|", stringsplitoptions.removeemptyentries);
                    dictionary<string,string> paradic = new dictionary<string, string>();
                    if (pramsetp!=null)
                    {
                        foreach (var p in pramsetp)
                        {
                            var plist = p.split("=");
                            paradic[plist[0]] = plist[1];
                        }
                    }
                    string pram = context.httpcontext.request.querystring.value.replace("?","");
                    requesturl = requesturl + "?";
                    var parmlist = pram.split("&");
                    if (parmlist!=null)
                    {
                        foreach (var s in parmlist)
                        {
                            var kv = s.split("=",stringsplitoptions.removeemptyentries);
                            if (kv!=null && kv.length>0)
                            {
                                string ve = "";
                                string k = kv[0];
                                if (kv.length>1)
                                {
                                    ve = kv[1];
                                }

                                requesturl = $"{requesturl}{paradic[k]}={ve}&";
                            }
                        }
                    }
                    requesturl = requesturl.remove(requesturl.length - 1);
                }
                context.result = new redirectresult(requesturl);
            }
        }
    }

第二步，在需要实现pc端页面适应移动端页面的控制器前加入过滤器，如

这样，在pc端访问文章类型页的时候返回的就是pc端页面，移动端请求的时候返回的就是移动端页面。当然也可以在移动端控制器加入，判断一下是否为pc端请求，如果为pc端请求就返回pc端的页面。