報錯資訊

　　The 'Access-Control-Allow-Origin' headeris present on the requested resource

解決方案

　　web.config配置資訊

  <appSettings xdt:Transform="Replace">
    <add key="cors_allowOrigins" value="http://localhost:8002,http://192.168.0.1:8002" />
  </appSettings>

　　不加上下面的配置項，跨域就不會生效，不知道為啥。

<system.webServer>
    <security>
      <requestFiltering>
        <requestLimits maxAllowedContentLength="
 
4294967295"></requestLimits>
      </requestFiltering>
    </security>
    <modules>
      <remove name="WebDAVModule" />
    </modules>
    <handlers>
      <remove name="WebDAV" />
      <remove name="ExtensionlessUrlHandler-Integrated-4.0" />
      <remove name="
 
OPTIONSVerbHandler" />
      <remove name="TRACEVerbHandler" />
      <add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="*" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
    </handlers>
  </system.webServer>

　　對應程式碼，初始化跨域配置　　

 　　public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
            //異常捕捉
            config.Filters.Add(new ApiErrorHandleAttribute());

            // Web API 配置和服務
            var allowOrigins = ConfigurationManager.AppSettings["cors_allowOrigins"];
            var globalCors = new EnableCorsAttribute(allowOrigins, "*", "*")
            {
                SupportsCredentials = true
            };
            config.EnableCors(globalCors);
            // Web API 路由
            config.MapHttpAttributeRoutes();

            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "api/{controller}/{id}",
                defaults: new { id = RouteParameter.Optional }
            );
        }
    }