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ASP.NET MVC 5 Keeping old input between requests

I need feature that is something similar to Laravel's old input helper but in MVC 5.
https://laravel.com/docs/5.6/requests#old-input
If validation fails, I need to reload all my model data as it was in the previous request except those inputs where user entered something wrong.
The problem is that my form has many disabled inputs and fields that program is fetching within [HttpGet] method, and they're getting lost during submission. So I need to store them in session.
The code below seems to work but is there any more efficient and beautiful way to do so with a less amount of code within each controller?
[HttpGet]
[Route(#"TaskManagement/Edit/{guid}")]
public async Task<ActionResult> Edit(Guid guid)
{
var model = new EditTaskViewModel();
model.Guid = guid;
await model.GetTaskFromRemoteService(new UserInfo(User));
ControllerHelpers.DisplayAlerts(model, this);
TempData["OldModel"] = model;
return View(model);
}
[HttpPost]
[ValidateAntiForgeryToken]
[Route(#"TaskManagement/Edit/{guid}")]
public async Task<ActionResult> Edit(EditTaskViewModel model, Guid guid, string submit)
{
model.Guid = guid;
if (ModelState.IsValid) {
await model.UpdateTaskInRemoteService(new UserInfo(User), submit);
ControllerHelpers.DisplayAlerts(model, this, "Task successfully updated");
if (model.ErrorCode == null)
return RedirectToAction("Edit", new { guid = model.Guid });
return RedirectToAction("Index");
}
if (TempData["OldModel"] != null) {
model = (EditTaskViewModel)TempData["OldModel"];
}
return View(model);
}

Using session state (including TempData) like this may break when you have multiple copies of the page open. You can work around this by generating a unique ID for the session key and storing it in a hidden field.
However, I would try to avoid using session altogether.
A simple approach is to use hidden fields to store the values that aren't sent to the server because they are in disabled fields.
A more robust approach is a separate class (or at least a private method) that knows how to setup your model for the first time and in transition (e.g. failed server validation). I call these classes "composers" and I describe the approach here.
Pseudocode for how an action method with a composer might look:
if( ModelState.IsValid ){
return Redirect();
}
var rebuiltModel = _composer.ComposeEdit( incomingModel );
return View( rebuiltModel );

I think the answer was quite simple. The shortest and easiest way is to populate the object from the database\remote service once more.
The fields that user entered whether they're valid or not will stay as they were before. The rest of them will load once again.

Bypass redundant code in controller

I have two methods in my controller that are called via ajax on click. Both do the exact same thing (retrieving the same data from a database) and return a partial view along with the model that contains the retrieved data. The only difference is the view.
public PartialViewResult FormA()
{
[...// Code]
return PartialView("_FormA", ModelWithData)
}
public PartialViewResult FormB()
{
[...// same Code as in FormA()]
return PartialView("_FormB", ModelWithData)
}
Both views use the same data but show different things.
If FormB() is called FormA() definitely has been called before.
There must be a way to bypass the second method/database request. It perceptibly slows down the application due to the additional database request.
My question seems really stupid to me, but I'm not able to find a workaround...
Thx for your help!

Yes sure by passing some kind of filter to your action method like below
public PartialViewResult ShowForm(string filter)
{
if(TempData["model"] == null)
{
[...// Code]
TempData["model"] = ModelWithData;
}
if(filter == "some_condition")
return PartialView("_FormA", TempData["model"] as ModelWithData);
else
return PartialView("_FormB", TempData["model"] as ModelWithData);
}
Got your point now. You can use any type of state management mechanish. Say TempData

ASP.Net MVC Refresh Page without destroying ViewModel

I want to create a multilingual webpage. To switch between languages I've got a dropdown on my page. If the change event of the dropdown gets fired the Method called "ChangeLanguage" in my Controller is called.
public ViewModels.HomeViewModel HVM { get; private set; }
// GET: Home
public ActionResult Index()
{
this.HVM = new ViewModels.HomeViewModel();
return View(this.HVM);
}
public JsonResult ChangeLanguage(int id) {
return Json(new {Success = true});
}
Now I'd like to to change my "SelectedLanguage" Property in my ViewModel (HVM) - but the Reference is null. May anyone explain why HVM is null in my ChangeLanguage Method?
After my SelectedLanguage Property is changed I'd like to reload my whole page to display it's texts in another language
e.g.
#model ViewModels.HomeViewModel
<html>
<div class="HeaderText">
Text = #{
#Model.TextToDisplay.Where(o =>
o.Language.Equals(Model.SelectedLanguage)).First()
}
</div>
Here's what I want to do in PseudoCode:
PseudoCode:
public JsonResult ChangeLanguage(int id) {
this.HVM.SelectedLanguage =
this.HVM.AvailableLanguages.Where(o =>
o.ID.Equals(id)).First();
Page.Reload();
return Json(new {Success = true});
}

May anyone explain why HVM is null in my ChangeLanguage Method?
Adhering to stateless nature of HTTP protocol, all (unless explicitly added into request header) requests (MVC method calls) loose state data associated with it. Web server treats every request a new request and creates new instances of classes right from controller itself.
In your case since it is a new request, controller has a HVM property defined but in ChangeLanguage it is not instantiated (it gets instantiated only into Index method which is not called when you invoke ChangeLanguage) hence it is null.
After my SelectedLanguage Property is changed I'd like to reload my
whole page to display it's texts in another language.
Option 1: Refresh page
Simple option to implement. Pass the language selection to server, server will return a new view with specific data. Drawback, whole page will refresh.
Option 2: Update view selectively
If option 1 is really not acceptable, then consider this option. There are multiple ways you can achieve it. Basically it involves either (a) breaking you view into partial view and update only the portion that is affect by selection or (b) bind data element with a JS object.
(a) - Not much need to be said for this.
(b) - Data binding can easily be done if you employ a JS library like KnockoutJS.

Change your methods to these methods , This trick will work for you =>pass your model to Change language from view. Also update JsonResult to ActionResult.
public ActionResult ChangeLanguage(ViewModels.HomeViewModel model,int id)
{
this.HVM.SelectedLanguage =
this.HVM.AvailableLanguages.Where(o =>
o.ID.Equals(id)).First();
return RedirectToAction("Index",model);
}
public ActionResult Index(ViewModels.HomeViewModel model)
{
if(model == null)
{
this.HVM = new ViewModels.HomeViewModel();
}
return View(this.HVM);
}

How to reload page with previously entered parameters?

I am working on a code project in Asp.net MVC. I have an issue with redirecting the user after they have completed an action. I have these controllers:
Index Search Page:
public ActionResult Index(){
//this method sets up viewmodel data for search preferences
Viewmodel obj = new Viewmodel();
//set values of dropdowns and searching capabilities
return View("Search", obj);
}
The user then fills out the search boxes in the view, chooses dropdowns. This will return a post search method that handles the data:
[HttpPost]
public ActionResult Index(Viewmodel obj, int? page)
{
data = from i in db.Database
select i;
if(!String.IsNullOrEmpty(obj.Example)
{
data = data.Where(x => x.poss == obj.poss);
}
//PAGING and other data formatting here
return View("Results", data);
}
Once the result list is displayed, I have a checkbox/button system in the result view that allows the user to select multiple results and mark them as "Good", "Bad" ETC. This is a method that changes the database very simply. My problem is that after the database alters the data, im not sure how to return the user back to the exact result set they were at. A method that returns void doesn't work, and the parameters are not separated, (one whole viewmodel), so i can't simply save the URL and return them back to the unique URL. I want to keep the viewmodel as the parameter. How can I save the viewmodel data that contains their search preferences for use later as well as the page number without changing my method to this:
[HttpPost]
public ActionResult Index(string dropdown1, string dropdown2, int num......){}

One thing I did was save view model to the session. Then I deserialize in the index method. Something like this in the index method:
[HttpGet]
public ActionResult AdvancedSearch()
{
HttpContext currentContext = System.Web.HttpContext.Current;
AdvancedSearchViewModel advancedSearchViewModel = (AdvancedSearchViewModel)Session["AdvancedSearchViewModel"];
if (advancedSearchViewModel == null)
{
advancedSearchViewModel = new AdvancedSearchViewModel();
AddAdvancedSearchLists(advancedSearchViewModel, currentContext);
}
return View(advancedSearchViewModel);
}
Here is some code to save to session in the post:
Session["AdvancedSearchViewModel"] = advancedSearchViewModel;
Note that if you have listboxes (drop down and multi select) you have to rebuild the listboxes in the post method and reselect the selections (for multi select). HTML is stateless. MVC does not send the listbox contents back to the server on the post, it only sends what was selected.

You can use TempData to achieve this.
Store ViewModel and Page in TempData within your POST Index action. The action method used to accept and store result status (i.e. good, bad, etc...) in the database will be able to access ViewModel and Page from the TempData given that it is the next immediate request. Once the database operation is done, just use RedirectToAction with the ViewModel and Page present in the TempData.
If the action which updates result status is not the next immediate request then you need to keep the data in session as answered by BGStack.

Message Box when item saved

Hi people I am new to this website was having trouble with my controller in C# MVC3 and when I gave up on looking for answers since i spent like 2 weeks on it I decided to join here.
The problem is I want a very simple confirmation message when I create a item in my application. I tried a If statement but I can't get the context correct. Can you kind people please help me thank you. My code:
//
// POST: /News/Create
[HttpPost]
public ActionResult Create(BooksItem booksitem)
{
try
{
using (var db = new BooksForever2())
{
db.NewsItems.Add(booksitem);
db.SaveChanges();
}
return RedirectToAction("Index");
}
catch
{
return View();
}
}
The create works fine I can add books and it saves but I want when it saves a message appears so it shows the user its has been saved. I have tried: Viewbag.Message("Saved")
But this does not work. Any help will be truly appreciated
Thank You

Just add this in you controller
TempData["Message"] = "Saved";
then in your view:
#if(TempData["Message"] != null)
{
<p>#TempData["Message"].ToString()</b> #* or whatever element you need to show*#
}
at your view level you can do anything with the message (maybe flash it with jQuery):
jquery: Flash messages
UPDATE: I replaced ViewBag with TempData because I noticed you are doing a redirect, in which case the ViewBag won't persist but TemData would

Where do you want that confirmation message displayed? On the same edit form you are already on, or back on the index/list page?
Right now at the end of your method, you are redirecting to the Index action/page:
return RedirectToAction("Index");
The result of that is that the Index page will be loaded, and it will be completely unaware of where it came from other that something was saved.
Your two options, as I see it, are:
1) Stay on the current page, and display the message. You can add that message to the ViewBag like as has already been mentioned:
ViewBag.Message = "Saved"`
And then display it like this:
#if(ViewBag.Message != null)
{
<p>#ViewBag.Message</p>
}
and then make sure you remove the RedirectToAction and just return the default View, otherwise will still bounce you to the Index page.
2) Or, you can redirect the user back to the Index page, passing the message to be displayed, and then have the Index page look for that message. So when you call RedirectToAction, include a query string parameter:
ViewBag.Message
return RedirectToAction("Index", new { Message="Saved" });
Which will redirect you to ".../yourControllerName/Index?Message=Saved". Then you can add this to your Index action method:
if(!string.IsNullOrEmpty(QueryString["Message"]))
{
ViewBag.Message = QueryString["Message"];
}
And include that same view code in your index view:
#if(ViewBag.Message != null)
{
<p>#ViewBag.Message</p>
}