I have a single model type to wrap up various models I want to use in my view:
public class QuestionViewData {
public Question Question { get; set; }
public IList<Answer> Answers { get; set; }
}
Now, in my question view I pull the data from the Question object - that's fine. Secondly I iterate through all Answer objects and pass them to a partial view:
<% foreach(Answer item in Model.Answers) { %>
<% Html.RenderPartial("ShowAnswer", item); %>
<% } %>
For each answer (in the partial view) I have some action buttons (like ratings). I'm using separate form POST's with hidden fields for every button.
The problem is that I can't post the whole QuestionViewData model to my action method cause I only have the Answer object as model in the partial view. However, I need to return the complete question view from that action that takes QuestionViewData as model.
How do I handle such situations?
Assuming your answers all contain the id of the question, you can post the answers to your controller method, and then populate the rest of your QuestionViewData model type by looking up the questions from the database again. You then return your QuestionViewData object to the view as usual.
As Robert Harvey said, you can look it up from database, but you could also store it in Session:
[HttpGet]
public ActionResult ShowQuestion(int id)
{
var questionModel = new QuestionViewData();
//populate questionModel
Session["CurrentlyHandledQuestion"] = questionModel;
return View(questionModel);
}
[HttpPost]
public ActionResult ManageAnswer(params)
{
var questionModel = (QuestionViewData)Session["CurrentlyHandledQuestion"];
}
Session data can be lost in many situations, so you should think about situation when questionModel is not available anymore in POST action, but it will work ok most of the time.
Related
How to require/validate parameters for actions. Right now I have lot of actions that looks like this (which is horrible):
public ActionResult DoSomething(string paramA, string paramB, string paramC)
{
if (string.IsNullOrWhiteSpace(paramA))
{
return JsonResult(false, "paramA is missing");
}
if (string.IsNullOrWhiteSpace(paramB))
{
return JsonResult(false, "paramB is missing");
}
if (string.IsNullOrWhiteSpace(paramC))
{
return JsonResult(false, "paramC is missing");
}
//Actual Code
}
How to encapsulte this (potentially "globally")? I know that its possible to wrap parameters to model and use ModelState.IsValid like in this post: https://stackoverflow.com/a/39538103/766304
That is maybe one step forward on same places but generally I don't that it's realistic to wrap all parameters to models everywhere (~1 class definition per 1 action method... how nice is that?).
Also this is again per action ceremony which should be handled somewhere centralized:
if (ModelState.IsValid == false)
{
return BadRequest(ModelState);
}
The easiest way to do it would be to create a model class and use [Required] attributes like this:
public class FooModel
{
[Required]
public string ParamA {get;set;}
[Required]
public string ParamB {get;set;}
[Required]
public string ParamC {get;set;}
}
And then use it in your controller like this:
public ActionResult DoSomething(FooModel model)
{
if (!ModelState.IsValid)
{
// return some errors based on ModelState
}
//Actual Code
}
If you are looking for more global approach, then i believe you could look into Action Filters and use OnActionExecuting filter and handle the validation there (haven't used that myself tho).
Here is how to do it:
How can I centralize modelstate validation in asp.net mvc using action filters?
That way your method would never be called if any of the parameters were missing.
The model annotations with [Required] [Length] and all these attributes is one of the most common ways to validate your model, specially it integrates with the Razor View engine and generates JavaScript validation as well, the same will happen if you are using EntityFramework for your back end, so this way you will have validation at the level of the UI, Controller and Data access.
You can also use Code Contracts which allows you to put pre and post conditions for your method in a nice way https://msdn.microsoft.com/en-us/library/dd264808(v=vs.110).aspx
If none of the above is still not enough, then you can add some checks in either your controller action or in your business domain service to make some business validation and return an error code if any errors found
Scenario: How to update a model?
ASP MVC 6
I am trying to update a model. For passing the model information to the client(browser/app) I am using the DTO.
Question 1: For updating, should I post the whole object back?
Question 2: Is there a way I can easily pass only the information that is updated? If yes, how?
Question 3: Can I use JSON Patch for updation?
Question 2: Is there a way I can easily pass only the information that
is updated? If yes, how?
Yes. You should create a view model which should have only those properties needed for the view.
Let's assume your use case is to build a view which allows user to edit only their last name.
public class EditUserViewModel
{
public int Id {set;get;}
public string LastName {set;get;}
}
And in your Get
public ActionResult Edit(int id)
{
var user = yourUserRepository.GetUser(id);
if(user!=null)
{
var v = new EditUserViewModel { Id=id,LastName=user.LastName};
return View(v);
}
return View("NotFound");
}
And the view
#model EditUserViewModel
#using(Html.BeginForm())
{
#Html.TextBoxFor(s=>S.LastName)
#Html.HiddenFor(s=>s.Id)
<input type="submit" id="saveBtn" />
}
and your HttpPost action
[HttpPost]
public ActionResult Edit(EditUserViewModel model)
{
// Since you know you want to update the LastName only,
// read model.LastName and use that
var existingUser = yourUserRepository.GetUser(model.Id);
existingUser.LastName = model.LastName;
yourUserRepository.Save();
// TO DO: redirect to success page
}
Assuming yourUserRepository is an object of your data access classes abstraction.
Question 1: For updating, should I post the whole object back?
Depends on what you want from the end user. With this view model approach, It is going to post only the Id and LastName and that is our use case.
Can I use JSON Patch for updating?
Since you are only sending the data which needs to be updated (partial data), you should be fine.
If you want,you may simply serialize your form data(which has only Id and LastName) and use jQuery post method to send it to your server.
$(function(){
$("#saveBtn").click(function(e){
e.preventDefault(); //prevent default form submit
var _form=$(this).closest("form");
$.post(_form.attr("action"),_form.serialize(),function(res){
//do something with the response.
});
});
});
To prevent overposting, you can use a binding whitelist using Bind attribute on your HttpPost action method. But the safest strategy is to use a view model class that exactly matches what the client is allowed to send.
Instead of this
UpdateModel(model);
You now can call this
await TryUpdateModelAsync(model);
I'm trying to better understand how to properly structure my ASP.NET MVC code to handle a situation where a single view contains multiple forms. I feel that it makes sense to submit the forms to their own action methods, so that each form can benefit from its own view model parameter binding and validation, and to avoid putting all form parameters into 1 larger, monolithic view model.
I'm trying to code this pattern, but I can't seem to tie the loose ends together.
I've written some example action methods below, along with example view model classes, that I think demonstrate what I'm trying to achieve. Lets say that I've got an Item Detail action method and view. On this Detail view, I've got two forms - one that creates a new Comment and another that creates a new Note. Both Comment and Note forms POST to their own action methods - DetailNewComment and DetailNewNote.
On success, these POST handler action methods work just fine. On an invalid model state though, I return View(model) so that I can display the issues on the original Detail view. This tries to render a view named Brief though, instead of Detail. If I use the overloaded View call that allows me to specify which view to render, then now I have issues with the different view model classes that I'm using. The specific view model classes now no longer work with the original DetailViewModel.
I get the feeling that I'm doing this completely wrong. How am I supposed to be handling this scenario with multiple forms? Thanks!
public ActionResult Detail(int id)
{
var model = new ItemDetailViewModel
{
Item = ItemRepository.Get(id)
};
return View(model);
}
[HttpPost]
public ActionResult DetailNewComment(int id, ItemDetailNewCommentViewModel model)
{
if (!ModelState.IsValid)
{
return View(model);
}
var comment = CommentRepository.Insert(new Comment
{
Text = model.Text
});
return RedirecToAction("Detail", new { id = id; });
}
[HttpPost]
public ActionResult DetailNewNote(int id, ItemDetailNewNoteViewModel model)
{
if (!ModelState.IsValid)
{
return View(model);
}
var note = NoteRepository.Insert(new Note
{
Text = model.Text
});
return RedirectToAction("Detail", new { id = id; });
}
... with view models something like ...
public class ItemDetailViewModel
{
public Item Item { get; set; }
}
public class ItemDetailNewCommentViewModel
{
public string Text { get; set; }
}
public class ItemDetailNewNoteViewModel
{
public string Text { get; set; }
}
For your case I'd recommend to have a master model for example your
ItemDetailViewModel class to which you'll add a property for each sub-model
public class ItemDetailViewModel
{
public Item Item { get; set; }
public ItemDetailNewCommentViewModel NewCommentModel {get;set;}
public ItemDetailNewNoteViewModel NoteModel {get;set;}
}
Your Detail view will be the master view and the other two will be partial views.
Master view will receive an instance of ItemDetailViewModel as model and inside view you will render your partials by passing Model.NewCommentModel and Model.NoteModel as their corresponding models. For being able to use separate actions for each form, instead of regular forms you can use ajax forms, thus you will send to the server only relevant information without altering the rest of the master view.
The chief problem here is what happens when the user messes up and their post doesn't pass validation server-side. If you choose to take them to a page where just the one form is presented, then you can post to a different action, but if you want both forms re-displayed, then they both should point to the same action.
Really, you just have to make a choice. I've seen sites handle it both ways. Personally, I prefer to re-display the original form, which means handling both forms in the same action. It can lead to bloat, but you can factor out a lot of logic from the action such that you end up with mostly just a branch depending on which form was submitted.
I don't know if this is the right way of doing this or not, but I am using Jquery and MVC2. I am using a the $.ajax method to make a call back to a controller to do some business logic on a .blur of a textbox.
I have two views that basically do the same thing with the common data, but are using different models. They both use the same controller. It might be easier to explain with code:
So here are the two models:
public class RecordModel {
public string RecordID { get; set; }
public string OtherProperties { get; set; }
}
public class SecondaryModel {
public string RecordID { get; set; }
public string OtherPropertiesDifferentThanOtherModel { get; set; }
}
There are two views that are strongly typed to these models. One is RecordModel, the other SecondaryModel.
Now on these views is a input="text" that is created via:
<%= Html.TextBoxFor(model => model.RecordID) %>
There is jQuery javascript that binds the .blur method to a call:
<script>
$('#RecordID').blur(function() {
var data = new Object();
data.RecordID = $('#RecordID').val();
// Any other stuff needed
$.ajax({
url: '/Controller/ValidateRecordID',
type: 'post',
dataType: 'json',
data: data,
success: function(result) {
alert('success: ' + result);
},
error: function(result) {
alert('failed');
}
});
}
</script>
The controller looks like:
[HttpPost]
public ActionResult ValidateRecordID(RecordModel model) {
// TODO: Do some verification code here
return this.Json("Validated.");
}
Now this works fine if I explicitly name the RecordModel in the controller for the View that uses the RecordModel. However, the SecondaryModel view also tries to call this function, and it fails because it's expecting the RecordModel and not the SecondaryModel.
So my question is this. How can two different strongly typed views use the same Action in a controller and still adhering to the modeling pattern? I've tried abstract classes and interfaces (and changing the view pages to use the Interface/abstract class) and it still fails.
Any help? And sorry for the robustness of the post...
Thanks.
You could define an interface for those classes.
interface IRecord
{
string RecordID { get; set; }
string OtherProperties { get; set; }
}
and make the method receive the model by using that:
[HttpPost]
public ActionResult ValidateRecordID(IRecord model)
{
// TODO: Do some verification code here
return this.Json("Validated.");
}
If you only need the RecordID, you can just have the controller method take int RecordID and it will pull that out of the form post data instead of building the view model back up and providing that to your action method.
[HttpPost]
public ActionResult ValidateRecordID(int RecordID) {
// TODO: Do some verification code here
return this.Json("Validated.");
}
There is no direct way of binding data to a interface/abstract class. The DefaultModelBinder will try to instantiate that type, which is (by definition) impossible.
So, IMHO, you should not use that option. And if you still want to share the same controller action between the two views, the usual way of doing that would be using a ViewModel.
Make your strongly-typed views reference that viewmodel. Make the single shared action receive an instance of it. Inside the action, you will decide which "real" model should be used...
If you need some parameter in order to distinguish where the post came from (view 1 or 2), just add that parameter to the ajax call URL.
Of course, another way is keeping what you have already tried (interface/abstract class), but you'll need a custom Model Binder in that case... Sounds like overcoding to me, but it's your choice.
Edit After my dear SO fellow #Charles Boyung made a gracious (and wrong) comment below, I've come to the conclusion that my answer was not exactly accurate. So I have fixed some of the terminology that I've used here - hope it is clearer now.
In the case above your action could accept two strings instead of a concrete type.
Another possibility is having two actions. Each action taking one of your types. I'm assuming that functionality each type is basically the same. Once the values have been extracted hand them off to a method. In your case method will probably be the same for each action.
public ActionResult Method1(Record record)
{
ProcessAction(record.id, record.Property);
}
public ActionResult Action2(OtherRecord record)
{
ProcessAction(record.id, record.OtherProperty);
}
private void ProcessAction(string id, string otherproperity)
{
//make happen
}
Here's a simplification of my real models in ASP.NET MVC, that I think will help focus in on the problem:
Let's say I have these two domain objects:
public class ObjectA
{
public ObjectB ObjectB;
}
public class ObjectB
{
}
I also have a view that will allow me to create a new ObjectA and that includes selecting one ObjectB from a list of possible ObjectBs.
I have created a new class to decorate ObjectA with this list of possibilities, this is really my view model I guess.
public class ObjectAViewModel
{
public ObjectA ObjectA { get; private set; }
public SelectList PossibleSelectionsForObjectB { get; private set; }
public ObjectAViewModel(ObjectA objectA, IEnumerable<Location> possibleObjectBs)
{
ObjectA = objectA;
PossibleSelectionsForObjectB = new SelectList(possibleObjectBs, ObjectA.ObjectB);
}
}
Now, what is the best way to construct my view and controller to allow a user to select an ObjectB in the view, and then have the controller save ObjectA with that ObjectB selection (ObjectB already exists and is saved)?
I tried creating a strongly-typed view of type, ObjectAViewModel, and binding a Html.DropDownList to the Model.PossibleSelectionsForObjectB. This is fine, and the I can select the object just fine. But getting it back to the controller is where I am struggling.
Attempted solution 1:
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Create(ObjectAViewModel objectAViewModel)
This problem here is that the objectAViewModel.ObjectA.ObjectB property is null. I was thinking the DropDownList which is bound to this property, would update the model when the user selected this in the view, but it's not for some reason.
Attempted solution 2:
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Create(ObjectA objectA)
This problem here is that the ObjectA.ObjectB property is null. Again, I thought maybe the DropDownList selection would update this.
I have also tried using the UpdateModel method in each of the above solutions, with no luck. Does anyone have any ideas? I'm guessing I'm missing a binding or something somewhere...
Thanks!
I use code as follows:
[HttpPost]
public ActionResult Create([Bind(Exclude = "Id")]ObjectA objectAToCreate)
{
try
{
Repository.AddObjectA(objectAToCreate);
return RedirectToAction("Details", new { id = objectAToCreate.Id });
}
catch
{
return View();
}
}
With the following code in a Repository (Entity Framework specific):
public void AddObjectA(ObjectA objectAToAdd)
{
objectAToAdd.ObjectB = GetObjectB(objectAToAdd.ObjectB.Id);
_entities.AddToObjectAs(objectAToAdd);
_entities.SaveChanges();
}
public void GetObjectB(int id)
{
return _entities.ObjectBs.FirstOrDefault(m => m.id == id);
}
As per your commments, it is essentially reloading the object from the underlying data service, however I didn't find the need to use the ModelState to access the attempted value.
This is based on a view coded along these lines:
<p>
<%= Html.LabelFor( f => f.ObjectB.Id) %>
<%= Html.DropDownList("ObjectB.Id", new SelectList((IEnumerable)ViewData["ObjectBList"], "Id", "Descriptor"),"") %>
<%= Html.ValidationFor( f => f.ObjectB, "*") %>
</p>
Note that this could be improved to use a strongly typed ViewModel (which I believe you already do) and also to create a custom Editor Template for ObjectB such that the call could be made using:
<%= Html.EditorFor( f => f.ObjectB ) %>
After some more research it doesn't look like this is a case ASP.NET MVC will take care of for me. Perhaps there is a data service binding model I can use (so MVC would automatically grab the appropriate object out of memory, based on what was selected in the dropdown), but for now, I can fix this by handling it in the controller:
Get the selected item from the dropdown using Controller.ModelState
Reload that ObjectB from the underlying data service
Assign that ObjectB to ObjectA.ObjectB
Save ObjectA
So my controller method looks like this now:
Edited based on the comment from LukLed
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Create(ObjectA objectA, string objectBStr)
{
ObjectB objectB = _objBService.Get(objectBStr);
objectA.ObjectB = objectB;
_objAService.Save(objectA);
return RedirectToAction("Details", new { id = objectA.Id });
}