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.
Related
In the Create action of the controller, based on user input, we plan to populate the model object with some data, to minimize data entry:
[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Create(Item item, string str)
{
// if only str is provided
if (string.IsNullOrEmpty(item.KeyInfo) && !string.IsNullOrEmpty(str))
{
Helpers.FillItemModel(item, str); //fill data
}
else if (ModelState.IsValid)
{
_context.Add(item);
await _context.SaveChangesAsync();
return RedirectToAction(nameof(Create));
}
return View(item);
}
However, although we can confirm the item object has been populated with data to several fields, by setting break point at the last line: return View(item), when the browser gets the response, all fields are empty.
But if we comment out the entire code segment, only leave the return statement and do a post with some data that was manually entered, the browser will receive correct data in all fields.
Thank you for your time.
To update ModelState value you have to reset the ModelState first as follows:
// if only str is provided
if (string.IsNullOrEmpty(item.KeyInfo) && !string.IsNullOrEmpty(str))
{
ModelState.Clear();
Helpers.FillItemModel(item, str); //fill data
}
ModelState.Clear() will reset the whole model. If you don't want that and just want to update few fields value keeping other field value intact then use ModelState["fieldName"].Value = "newValue in your helper class.
I have an action
public ActionResult Index(string search)
{
var listingModel = Repository.Search(search); //gets from DB items. Model doesn't include 'serach' string as property or field
return View("Index", listingModel)
}
The View contains filter area with text box (this code from extension method for helper):
htmlHelper.TextBox("Search", null, htmlAttributesDictionary);
I've noticed that it automatically inserts value of 'search' parameter into textbox. But my problem is that I cannot find how it gets it. I cannot see the source code of .TextBox() helper. I cannot find this value in htmlHelper.ViewData.Model. I want to change value of search parameter (I need to save it is Session and gets from session). Do you know what I can write in the controller action that will automatically sets my value from session into the checkbox.
I know that I can just use redirect, but it doesn't seem to be correct way. It looks for me not very beautiful:
public ActionResult Index(string search)
{
search = GetFromSession();
return RedirectToAction("Index", new {search = search});
var listingModel = Repository.Search(search); //gets from DB items. Model doesn't include 'serach' string as property or field
return View("Index", listingModel)
}
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.
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);
}
I have 2 Action methods in one controller,
Index:
public ActionResult Index(string url)
{
// take the url as a param and do long tasks here
ViewBag.PageTitle = "title";
ViewBag.Images = "images";
// and some more view bags
return View();
}
This index view contains a form which post to another method in the same controller.
public ActionResult PostMessage(string msg, string imgName)
{
// save data in the db
// but on error I want to navigate back to the Index view but without losing data the user fielded before submit the form.
// Also need to pass an error message to this index view to show
}
How to return back to Index view if something went wrong in the PostMessage method, and also don't clear the form fields, plus showing an error message which the PostMessage method specified.
I need to know the best practice for doing such a scenario.
The best approach is usually to create a ViewModel type for your form. Add attributes to the properties of that model to define what would make it "wrong." Make your form use methods like #Html.TextBoxFor the various fields. Then have your PostMessage class take an object of that type, rather than taking the message and image name directly. Then you can validate the model and return the view again if the model is invalid.
See http://weblogs.asp.net/scottgu/archive/2010/01/15/asp-net-mvc-2-model-validation.aspx for some code examples following this pattern.
You could specify the name of the view you want to return:
public ActionResult PostMessage(string msg, string imgName)
{
if (SomeErrorWhileSavingInDb)
{
// something wrong happened => we could add a modelstate error
// explaining the reason and return the Index view.
ModelState.AddModelError("key", "something very wrong happened when trying to process your request");
return View("Index");
}
// everything went fine => we can redirect
return RedirectToAction("Success");
}
Just redirect back to the Index action
return RedirectToAction("Index");
There are overloads for this method that allows you to pass route values and other information.