in MVC

When to use TempData in ASP.NET MVC

The problem

I came across this problem where I had a basic list of items and for each if these items I wanted to add a delete action on my controller. I wanted to add some error checking around the delete action so if someone attempted to modify the URL and enter a incorrect parameter into my controller, I wanted to redirect back to the previous controller and notify the user of this mistake. Take this example. I have a Product Controller and the Index Action and View lists all of the products. I have a delete action on the Product Controller which checks if the productId parameter is valid and then removes the product and redirects to the Index action using the RedirectToAction method.

The solution

When validating the productId, if its NOT valid simply add a new key/value to the TempData object and call the RedirectToAction method. TempData stores data for short periods of time for the current and next HTTP request. In your index view, you can check to see if your key/value pair exists and display a error message. If you refresh the page, you will notice the data from the TempData will be gone. Remember to use RedirectToAction where possible as this is more friendly with Unit Testing rather than using the HttpResponse redirect method.

This reference illustrates a good understanding between TempData, ViewBag and ViewData.