Tell Actions/Controllers to Persist TempData

Question

I understand that TempData is designed to work only between a single page request. But I think have a situation I think breaks the intended functionality.

I use Controllers in preference to Handlers for delivering images. I don't now if that is best practice, but it works very well for me. The problem though, is that each call to one of the image Actions obviously uses up a TempData credit.

Is there a way in MVC to say "This Controller/Action is out of the scope of normal page requests" and therefore either persist the TempData or remove itself from the TempData life cycle completely?

Rich

Answer 1

My solution has been to create an Attribute that persists the TempData across page requests. My initial reaction to this is "yuck", but I want to effectively exclude any controllers decorated with the Attribute from the TempData lifecycle.

using System.Web.Mvc;

namespace K3R.Web.Mvc.Filters {
    public sealed class PersistTempDataAttribute : ActionFilterAttribute {
        public PersistTempDataAttribute() { }

        public override void OnActionExecuting(ActionExecutingContext filterContext) {
            var tempData = filterContext.Controller.TempData;
            if (tempData == null || tempData.Count == 0)
                return;

            string[] keys = new string[tempData.Keys.Count];
            tempData.Keys.CopyTo(keys, 0);
            foreach (var key in keys)
                tempData[key] = tempData[key];
        }
    }
}

Any feedback on a better solution would be appreciated.

Rich

Answer 2

I'm not sure of the exact answer to this as I'm pretty new to MVC myself. However, I have heard of people having trouble with AJAX requests killing off the TempData before they wanted it to as well.

I guess you could implement your own Session based system to store this information?

I'm sure someone else will have a more complete answer for you soon, though!

Answer 3

I do not completely understand your way of doing it and why but I would rather go with handlers. Or if you stick to controller actions, I can say that this worked for me fine without any issues for delivering images on-the-fly and I used FileContentResult in my controller actions.

Like this:

        return File(imageBytes, imageType);

You get the bytes out of datastore or somewhere..

hope it helps