Does Html.TextBox uses Request.Params instead of Model?

Question

I have a simple test application:

Model:

public class Counter
{
    public int Count { get; set; }

    public Counter()
    {
        Count = 4;
           


        

Answer 1

Html.TextBox() uses internally ViewData.Eval() method which first attempts to retrieve a value from the dictionary ViewData.ModelState and next to retrieve the value from a property of the ViewData.Model. This is done to allow restoring entered values after invalid form submit.

Removing Count value from ViewData.ModelState dictionary helps:

public ActionResult Increment(Counter counter)
{
    counter.Count++;
    ViewData.ModelState.Remove("Count");
    return View(counter);
}

Another solution is to make two different controller methods for GET and POST operations:

public ActionResult Increment(int? count)
{
    Counter counter = new Counter();

    if (count != null)
        counter.Count = count.Value;

    return View("Increment", counter);
}

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Increment(Counter counter)
{
    counter.Count++;

    return RedirectToAction("Increment", counter);
}

Counter object could also be passed via TempData dictionary.

You may also be interested in the article Repopulate Form Fields with ViewData.Eval() by Stephen Walther.