I am assuming (please correct me if I am wrong) that you want to re-display the edit page if the edit fails and to do this you are using a redirect.
You may have more luck by just returning the view again rather than trying to redirect the user, this way you will be able to use the ModelState to output any errors too.
Edit:
Updated based on feedback. You can place the previous URL in the viewModel, add it to a hidden field then use it again in the action that saves the edits.
For instance:
public ActionResult Index()
{
return View();
}
[HttpGet] // This isn't required
public ActionResult Edit(int id)
{
// load object and return in view
ViewModel viewModel = Load(id);
// get the previous url and store it with view model
viewModel.PreviousUrl = System.Web.HttpContext.Current.Request.UrlReferrer;
return View(viewModel);
}
[HttpPost]
public ActionResult Edit(ViewModel viewModel)
{
// Attempt to save the posted object if it works, return index if not return the Edit view again
bool success = Save(viewModel);
if (success)
{
return Redirect(viewModel.PreviousUrl);
}
else
{
ModelState.AddModelError("There was an error");
return View(viewModel);
}
}
The BeginForm method for your view doesn't need to use this return URL either, you should be able to get away with:
@model ViewModel
@using (Html.BeginForm())
{
...
<input type="hidden" name="PreviousUrl" value="@Model.PreviousUrl" />
}
Going back to your form action posting to an incorrect URL, this is because you are passing a URL as the 'id' parameter, so the routing automatically formats your URL with the return path.
This won't work because your form will be posting to an controller action that won't know how to save the edits. You need to post to your save action first, then handle the redirect within it.