Postback values getting lost!

I have a controller with typical create methods (one for GET, one for POST). the POST takes a strongly-typed parameter:

[HttpPost] public ActionResult Create(Quiz entity)

however, when the callback is mad开发者_运维百科e, the properties of my entity are null... if I redefine it like this:

[HttpPost] public ActionResult Create(Quiz entity, FormCollection form)

I can see that the values are there e.g. form["Component"] contains "1". I've not had this problem in the past and I can't figure out why this class would be different.

thoughts anyone?

The easiest way to get the default model binder to instantiate Quiz for you on postback is to use the Html form helpers in you view. So, for example, if your Quiz class looked like this:

public class Quiz
{
    public int Id { get; set; }
    public string Name { get; set; }
}

The following code in your view would ensure the values are present on postback:

@Html.HiddenFor(mod => mod.Id)
@Html.TextBoxFor(mod => mod.Name)

Keep in mind that values which need to be posted back but not shown in the view (like identifiers) need to be added to the view with Html.HiddenFor.

Here's a more comprehensive list of Html form helper functions.

I FIGURED IT OUT!!

so, in my model (see comments on @ataddeini's thread below) you can see I have a Component... to represent components I used a couple of listboxes, the second (Components) dependent on the contents of the first (Products). In generating the second list I used

@Html.DropDownListFor(x => x.Component, ...)

which (as shown in one of the above links) generates a form field called "Component"... and therein lies the problem. What I needed to have done is bind it to the the Id of the component instead!

@Html.DropDowListFor(x => x.Component.Id, ...)

hurray!