Telerik Reporting REST API not accepting cross origin requests

[Zach]

My API has a `ReportsController` set up like so:

using System.Web.Http.Cors;
using Telerik.Reporting.Cache.File;
using Telerik.Reporting.Services;
using Telerik.Reporting.Services.WebApi;

namespace API.Controllers
{
[EnableCors(origins: "*", headers: "*", methods: "*")]
public class ReportsController : ReportsControllerBase
{
static ReportServiceConfiguration configurationInstance;

static ReportsController()
{
configurationInstance = new ReportServiceConfiguration
{
HostAppId = "Html5App",
Storage = new FileStorage(),
ReportResolver = new ReportTypeResolver(),
// ReportSharingTimeout = 0,
// ClientSessionTimeout = 15,
};
}

public ReportsController()
{
//Initialize the service configuration
this.ReportServiceConfiguration = configurationInstance;
}
}
}

My `App_Start\WebApiConfig.cs`:

    public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
            // Web API configuration and services

            config.EnableCors();
            // Web API routes
            config.MapHttpAttributeRoutes();

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

My `Global.asax.cs`:

    public class WebApiApplication : System.Web.HttpApplication
    {
        protected void Application_Start()
        {
            ReportsControllerConfiguration.RegisterRoutes(GlobalConfiguration.Configuration);
            GlobalConfiguration.Configure(WebApiConfig.Register);
        }
    }

My `web.config` has the recommended binding redirects:

    <dependentAssembly>
        <assemblyIdentity name="System.Web.Http" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-5.2.6.0" newVersion="5.2.6.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Net.Http.Formatting" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-5.2.6.0" newVersion="5.2.6.0" />
      </dependentAssembly>

As far as I can tell, everything is set up correctly, I can call `api/reports/formats` and see the correct data.  When I try to load this report, I get an error.

$("#reportViewer1").telerik_ReportViewer({
serviceUrl: "http://dev-api/api/reports",
reportSource: {
report: "Logic.Reports.Report1, Logic",
parameters: reportParam
},
});

It displays:
"Error loading the report viewer's templates. (Template = http://dev-api/api/reports/resources/templates/telerikReportViewerTemplate-html)." 

on the page, and displays 

`Failed to load http://dev-api/api/reports/resources/templates/telerikReportViewerTemplate-html: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:64634' is therefore not allowed access.`

in the Chrome console.  I cannot figure out what I am missing.

[Silviya]

Hi Zach,

I did some testing and it seems that the binding redirects are causing the issue. I added proper binding redirects for the referenced assemblies (in my case the assemblies are referring version 5.2.3.0, but you can replace it with your current version). For example:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Http" culture="neutral" publicKeyToken="31bf3856ad364e35"/>
        <bindingRedirect oldVersion="0.0.0.0-65535.65535.65535.65535" newVersion="5.2.3.0"/>
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Net.Http.Formatting" culture="neutral" publicKeyToken="31bf3856ad364e35"/>
        <bindingRedirect oldVersion="0.0.0.0-65535.65535.65535.65535" newVersion="5.2.3.0"/>
      </dependentAssembly>
    </assemblyBinding>
  </runtime>
</configuration>

For more information, please refer to How To: Add Telerik Reporting REST Web API to Web Application (step 2).
I'm also attaching a video record with steps to enable CORS. Note that the video is silent, in .swf format that can be opened in browser with installed Flash plugin.

Regards,
Silviya
Progress Telerik