webapi踩的坑

    "Access-Control-Allow-Origin" value="*" />
        
        "Access-Control-Allow-Methods" value="GET, POST, PUT, DELETE, OPTIONS" />
        
        "Access-Control-Allow-Headers" value="x-requested-with,content-type" />
        
        "Access-Control-Request-Methods" value="GET, POST, PUT, DELETE, OPTIONS" />
        
      

GlobalConfiguration.Configuration.Formatters.XmlFormatter.SupportedMediaTypes.Clear();
            //默认返回 json  
            GlobalConfiguration.Configuration.Formatters.JsonFormatter.MediaTypeMappings.Add(
                new QueryStringMapping("datatype", "json", "application/json"));

            // 解决json序列化时的循环引用问题
            config.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;

protected void Application_BeginRequest(object sender, EventArgs e)
        {
            var res = HttpContext.Current.Response;
            var req = HttpContext.Current.Request;

            //自定义header时进行处理
            if (req.HttpMethod == "OPTIONS")
            {
                res.AppendHeader("Access-Control-Allow-Headers", "Content-Type, X-CSRF-Token, X-Requested-With, Accept, Accept-Version, Content-Length, Content-MD5, Date, X-Api-Version, X-File-Name,Token,Cookie");
                res.AppendHeader("Access-Control-Allow-Methods", "POST,GET,PUT,PATCH,DELETE,OPTIONS");
                res.StatusCode = 200;
                res.End();
            }
        }