MVC3 Form Posted Value - asp.net-mvc

Question

Below Scenario, I think I must see the START text in my form when first loaded.
When I click send data button and submit, I was waiting to see FINISH text in my form.
Buy the START text never changes when I click the button and post the form...
Anybody can tell the problem?
MY CONTROLLER:
namespace MvcApplication1.Controllers
{
public class BuyController : Controller
{
public ActionResult Index(BuyModel model)
{
if (Request.HttpMethod == "GET")
{
model.Message= "START";
return View(model);
}
else
{
BuyModel newModel = new BuyModel();
newModel.Message= "FINISH";
return View(newModel);
}
}
}
}
MY VIEW :
#model MvcApplication1.Models.BuyModel
#using (Html.BeginForm("Index", "Buy", FormMethod.Post))
{
#Html.TextBoxFor(s => s.Message)
<button type="submit" >Send</button>
}
MY MODEL:
public class BuyModel
{
public string Message { get; set; }
}

Answer 1

public class BuyController : Controller
{
public ActionResult Index()
{
BuyModel model = new BuyModel();
model.Message= "START";
return View(model);
}
[HttpPost]
public ActionResult Index(BuyModel model)
{
model = new BuyModel();
model.Message= "FINISH";
ModelState.Clear(); // the fix
return View(model);
}
}
View:
#model MvcApplication1.Models.BuyModel
#using (Html.BeginForm("Index", "Buy"))
{
#Html.TextBoxFor(s => s.Message)
<button type="submit" >Send</button>
}
Your issue is because your original code, that Action Method will only be executed as an HTTP GET request. ASP.NET MVC allows you to specify a post with the [HttpPost] attribute (see above code).
I'm not sure what you are getting at with your POST desired-behavior. It seems like you are just wiping out whatever form values are pushed on the POST. So modify my above code accordingly, but it should give you the general idea.
Edit: it seems to be that the text box is retaining its value after the POST. It's not just with "START", but if you type anything into that text box and hit submit, you'll have a POST with the exact same text in the text box that was there when you submitted the form.
Edit Edit: see the changed code. Call ModelState.Clear() in your POST action method and you'll have the right value reflected.

Answer 2

If you are posting, and not returning a RedirectResult, by default the helpers will use the value from ModelState. You either need to clear ModelState or have a different approach.
The PRG (post redirect get) pattern in MVC is very important. So if its a post, and you aren't redirecting, the helpers assume there is an error that needs to be corrected and the value is pulled from ModelState.