Asp.net mvc checkbox checked from the action

Question: I have to check the checkbox(which is not part of model) from the action ? If I select the checkbox and submit to post action, then call the view again the checkbox will be checked fine. But how to check it on first place from non-post action please ? Thanks!

public ActionResult Images(string params)
{
//some code
return View(cp);
}

[HttpPost]
public ActionResult Images(string chbx)
{
//some code
}  

Images view:

@using (Html.BeginForm())
{
    @Html开发者_如何学C.CheckBox("chbx")
} 

I'm using MVC3 by the way.

---

do you mean @Html.CheckBox("chbx", true) ?