An improved HTTPS redirection filter for ASP.NET MVC.

CustomRequireHttpsFilter.cs

public class CustomRequireHttpsFilter : RequireHttpsAttribute
{
    protected override void HandleNonHttpsRequest(AuthorizationContext filterContext)
    {
        // The base only redirects GET, but we added HEAD as well. This avoids exceptions for bots crawling using HEAD.
        // The other requests will throw an exception to ensure the correct verbs are used. 
        // We fall back to the base method as the mvc exceptions are marked as internal. 

        if (!String.Equals(filterContext.HttpContext.Request.HttpMethod, "GET", StringComparison.OrdinalIgnoreCase) 
            && !String.Equals(filterContext.HttpContext.Request.HttpMethod, "HEAD", StringComparison.OrdinalIgnoreCase))
        {
            base.HandleNonHttpsRequest(filterContext);
        }            

        // Redirect to HTTPS version of page
        // We updated this to redirect using 301 (permanent) instead of 302 (temporary).
        string url = "https://" + filterContext.HttpContext.Request.Url.Host + filterContext.HttpContext.Request.RawUrl;

        if (string.Equals(filterContext.HttpContext.Request.Url.Host, "localhost", StringComparison.OrdinalIgnoreCase))
        {                
            // For localhost requests, default to IISExpress https default port (44300)
            url = "https://" + filterContext.HttpContext.Request.Url.Host + ":44300" + filterContext.HttpContext.Request.RawUrl;
        }

        filterContext.Result = new RedirectResult(url, true);
    }
}