asp.net mvc - CORS in ASP .NET MVC5

Question

I have a MVC project in which I have a couple of JSON controller methods I want to expose cross domain. Not the entire site, just these two methods.

I basically want to to the exact thing stated in this post for cors:

http://enable-cors.org/server_aspnet.html

However, the problem is that I have a regular MVC project and not a WEB API, meaning, that I cannot follow the steps regaring the register

public static void Register(HttpConfiguration config)
{
    // New code
    config.EnableCors();
}

method since it is not present in my MVC project.

Is there a way to use this library although it is a MVC project?

I'm aware of that I can config this through web.config using:

<httpProtocol>
      <customHeaders>
        <clear />
        <add name="Access-Control-Allow-Origin" value="http://www.domain.com" />
      </customHeaders>
</httpProtocol>

But I don't want to expose all methods, and I want to specify more than one domain (2 domains) to have access to my methods...

Answer 1

As described in here: Setting Access-Control-Allow-Origin in ASP.Net MVC - simplest possible method

You should just create an action filter and set the headers there. You can use this action filter on your action methods wherever you want.

public class AllowCrossSiteJsonAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        filterContext.RequestContext.HttpContext.Response.AddHeader("Access-Control-Allow-Origin", "*");
        base.OnActionExecuting(filterContext);
    }
}

If you want to add multiple domains, you can't just set the header multiple times. In your action filter you will need to check if the requesting domain is from your list of domains and then set the header.

    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        var domains = new List<string> {"domain2.com", "domain1.com"};

        if (domains.Contains(filterContext.RequestContext.HttpContext.Request.UrlReferrer.Host))
        {
            filterContext.RequestContext.HttpContext.Response.AddHeader("Access-Control-Allow-Origin", "*");
        }

        base.OnActionExecuting(filterContext);
    }