WebAPI IE8、IE9 跨域问题

关于WebAPI跨域的问题，网上已经很多了，以下方案可以解决很多跨域问题，但是都不支持IE8、IE9浏览器，JSONP也只能支持Get请求

1. 通过dll配置 Install-Package Microsoft.AspNet.WebApi.Cors
2. 配置 Web.config

IE8，IE9跨域是通过XDomainRequest这个对象去实现，和XMLHttpRequest类似，可以参考下面文档

https://msdn.microsoft.com/zh-cn/library/dd573303(v=vs.85).aspx

使用jQuery.ajax的基础上，在jQuery下面再引用

https://github.com/MoonScript/jQuery-ajaxTransport-XDomainRequest/blob/master/jQuery.XDomainRequest.js

这样IE8、IE9跨域成功了

        public Response<string> Post()
        {
            Response<string> rs = new Response<string>
            {
                head = new ResponseHeader { errcode = , errmessage = "post" },
                data = "hello"
            };
            return rs;
        }

这样IE8、IE9跨域失败了

        public Response<string> Post(Request<Message> request)
        {
            Response<string> rs = new Response<string>
            {
                head = new ResponseHeader { errcode = , errmessage = "post" },
                data = request.data.content
            };
            return rs;
        }

后来通过排查，有对象形参的WebAPI就会遇到反序列化问题，（IE8,IE9）转换为request对象的時候报错

试了很多次，前端帶不过來Content-Type,就想到了用參数传递到后端，也修改了jQuery.XDOmainRequest.js这个文件

 /*!
  * jQuery-ajaxTransport-XDomainRequest - v1.0.4 - 2015-03-05
  * https://github.com/MoonScript/jQuery-ajaxTransport-XDomainRequest
  * Copyright (c) 2015 Jason Moon (@JSONMOON)
  * Licensed MIT (/blob/master/LICENSE.txt)
  */
 (function (factory) {
     if (typeof define === 'function' && define.amd) {
         // AMD. Register as anonymous module.
         define(['jquery'], factory);
     } else if (typeof exports === 'object') {
         // CommonJS
         module.exports = factory(require('jquery'));
     } else {
         // Browser globals.
         factory(jQuery);
     }
 }(function ($) {

     // Only continue if we're on IE8/IE9 with jQuery 1.5+ (contains the ajaxTransport function)
     if ($.support.cors || !$.ajaxTransport || !window.XDomainRequest) {
         return $;
     }

     var httpRegEx = /^(https?:)?\/\//i;
     var getOrPostRegEx = /^get|post$/i;
     var sameSchemeRegEx = new RegExp('^(\/\/|' + location.protocol + ')', 'i');

     // ajaxTransport exists in jQuery 1.5+
     $.ajaxTransport('* text html xml json', function (options, userOptions, jqXHR) {

         // Only continue if the request is: asynchronous, uses GET or POST method, has HTTP or HTTPS protocol, and has the same scheme as the calling page
         if (!options.crossDomain || !options.async || !getOrPostRegEx.test(options.type) || !httpRegEx.test(options.url) || !sameSchemeRegEx.test(options.url)) {
             return;
         }

         var xdr = null;

         return {
             send: function (headers, complete) {
                 var postData = '';
                 var userType = (userOptions.dataType || '').toLowerCase();

                 xdr = new XDomainRequest();
                 if (/^\d+$/.test(userOptions.timeout)) {
                     xdr.timeout = userOptions.timeout;
                 }

                 xdr.ontimeout = function () {
                     complete(500, 'timeout');
                 };

                 xdr.onload = function () {
                     var allResponseHeaders = 'Content-Length: ' + xdr.responseText.length + '\r\nContent-Type: ' + xdr.contentType;
                     var status = {
                         code: 200,
                         message: 'success'
                     };
                     var responses = {
                         text: xdr.responseText
                     };
                     try {
                         if (userType === 'html' || /text\/html/i.test(xdr.contentType)) {
                             responses.html = xdr.responseText;
                         } else if (userType === 'json' || (userType !== 'text' && /\/json/i.test(xdr.contentType))) {
                             try {
                                 responses.json = $.parseJSON(xdr.responseText);
                             } catch (e) {
                                 status.code = 500;
                                 status.message = 'parseerror';
                                 //throw 'Invalid JSON: ' + xdr.responseText;
                             }
                         } else if (userType === 'xml' || (userType !== 'text' && /\/xml/i.test(xdr.contentType))) {
                             var doc = new ActiveXObject('Microsoft.XMLDOM');
                             doc.async = false;
                             try {
                                 doc.loadXML(xdr.responseText);
                             } catch (e) {
                                 doc = undefined;
                             }
                             if (!doc || !doc.documentElement || doc.getElementsByTagName('parsererror').length) {
                                 status.code = 500;
                                 status.message = 'parseerror';
                                 throw 'Invalid XML: ' + xdr.responseText;
                             }
                             responses.xml = doc;
                         }
                     } catch (parseMessage) {
                         throw parseMessage;
                     } finally {
                         complete(status.code, status.message, responses, allResponseHeaders);
                     }
                 };

                 // set an empty handler for 'onprogress' so requests don't get aborted
                 xdr.onprogress = function () { };
                 xdr.onerror = function () {
                     complete(500, 'error', {
                         text: xdr.responseText
                     });
                 };

                 if (userOptions.data) {
                     postData = ($.type(userOptions.data) === 'string') ? userOptions.data : $.param(userOptions.data);
                 }
                 if (options.contentType && options.contentType.length > 0) {
                     if (options.url.indexOf('?') > -1) {
                         options.url = options.url + '&_contentType=' + options.contentType;
                     } else {
                         options.url = options.url + '?_contentType=' + options.contentType;
                     }
                 }
                 xdr.open(options.type, options.url);
                 xdr.send(postData);
             },
             abort: function () {
                 if (xdr) {
                     xdr.abort();
                 }
             }
         };
     });

     return $;

 }));

jQuery.XDomainRequest.js

加上消息处理就可以解决

 public class CrossDomainFixIEHandler : DelegatingHandler
    {
        protected override System.Threading.Tasks.Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken)
        {
            if (request.Method == HttpMethod.Options)
            {
                HttpResponseMessage response = request.CreateResponse<string>(HttpStatusCode.OK, null);
                TaskCompletionSource<HttpResponseMessage> tcs = new TaskCompletionSource<HttpResponseMessage>();
                tcs.SetResult(response);
                return tcs.Task;
            }
            if (request.Content.Headers.ContentType == null || string.IsNullOrWhiteSpace(request.Content.Headers.ContentType.MediaType))
            {
                string contentType = this.GetContentType(string.Concat(request.RequestUri.Query, "&"));
                if (string.IsNullOrWhiteSpace(contentType))
                {
                    contentType = "application/json";
                }
                request.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue(contentType);
            }
            return base.SendAsync(request, cancellationToken);
        }

        /// <summary>
        /// 獲取ContentType
        /// </summary>
        /// <param name="source"></param>
        /// <returns></returns>
        private string GetContentType(string source)
        {
            if (string.IsNullOrWhiteSpace(source))
            {
                return string.Empty;
            }
            Regex regex = new Regex("[&?]_contentType=(?<contentType>(.*?))&", RegexOptions.IgnoreCase);
            Match match = regex.Match(source);
            if (match.Success)
            {
                return match.Groups["contentType"].Value;
            }
            else
            {
                return string.Empty;
            }
        }

完