How can I return the result of a different action or move the user to a different action if there is an error in my ModelState without losing my ModelState information?
In case this is useful to anyone I used @bob 's recommended solution using PRG:
see item 13 -> link.
I had the additional issue of messages being passed in the VeiwBag to the View being written and checked / loaded manually from TempData in the controller actions when doing a RedirectToAction("Action")
. In an attempt to simplify (and also make it maintainable) I slightly extended this approach to check and store/load other data as well. My action methods looked something like:
[AcceptVerbs(HttpVerbs.Post)]
[ExportModelStateToTempData]
public ActionResult ChangePassword(ProfileViewModel pVM) {
bool result = MyChangePasswordCode(pVM.ChangePasswordViewModel);
if (result) {
ViewBag.Message = "Password change success";
else {
ModelState.AddModelError("ChangePassword", "Some password error");
}
return RedirectToAction("Index");
}
And my Index Action:
[ImportModelStateFromTempData]
public ActionResult Index() {
ProfileViewModel pVM = new ProfileViewModel { //setup }
return View(pVM);
}
The code in the Action Filters:
// Following best practices as listed here for storing / restoring model data:
// http://weblogs.asp.net/rashid/archive/2009/04/01/asp-net-mvc-best-practices-part-1.aspx#prg
public abstract class ModelStateTempDataTransfer : ActionFilterAttribute {
protected static readonly string Key = typeof(ModelStateTempDataTransfer).FullName;
}
:
public class ExportModelStateToTempData : ModelStateTempDataTransfer {
public override void OnActionExecuted(ActionExecutedContext filterContext) {
//Only export when ModelState is not valid
if (!filterContext.Controller.ViewData.ModelState.IsValid) {
//Export if we are redirecting
if ((filterContext.Result is RedirectResult) || (filterContext.Result is RedirectToRouteResult)) {
filterContext.Controller.TempData[Key] = filterContext.Controller.ViewData.ModelState;
}
}
// Added to pull message from ViewBag
if (!string.IsNullOrEmpty(filterContext.Controller.ViewBag.Message)) {
filterContext.Controller.TempData["Message"] = filterContext.Controller.ViewBag.Message;
}
base.OnActionExecuted(filterContext);
}
}
:
public class ImportModelStateFromTempData : ModelStateTempDataTransfer {
public override void OnActionExecuted(ActionExecutedContext filterContext) {
ModelStateDictionary modelState = filterContext.Controller.TempData[Key] as ModelStateDictionary;
if (modelState != null) {
//Only Import if we are viewing
if (filterContext.Result is ViewResult) {
filterContext.Controller.ViewData.ModelState.Merge(modelState);
} else {
//Otherwise remove it.
filterContext.Controller.TempData.Remove(Key);
}
}
// Restore Viewbag message
if (!string.IsNullOrEmpty((string)filterContext.Controller.TempData["Message"])) {
filterContext.Controller.ViewBag.Message = filterContext.Controller.TempData["Message"];
}
base.OnActionExecuted(filterContext);
}
}
I realize my changes here are a pretty obvious extension of what was already being done with the ModelState by the code @ the link provided by @bob - but I had to stumble on this thread before I even thought of handling it in this way.