I've been reading too many tutorials already and none of it explain what this means in an action result
return View(model);
Why can't we simple return view?
Why do we put a model parameter in our action result's return view()?
Also, anyone can give an example for a situation where I have to use return view(model)?
Because your view uses the model to build its content.
If you had a model like this:
public class Order
{
public decimal Total { get; set; }
}
And your controller:
public ActionResult GetOrderInformation(int orderID)
{
var order = LoadOrder(orderID);
return View(order);
}
With this view:
#model Order
<html>
<head> </head>
<body>
Your order costs #Model.Total
</body>
</html>
You can see how the view is completely independent from the controller, or how the information is retrieved - which is the whole idea behind MVC. The view only knows about the model, and how to display the model - nothing else.
The controller knows who to ask for the data, but not how to display it
You don't need to.
If the view you are rendering is static with no info needed from the controller then you can just end your Action with a return View();
public ActionResult SomeAction()
{
...
return View();
}
Then in your .cshtml file don't declare any #model directive and it'll be fine.
You can return simply view, but when you pass the model into view your can use it as you viewbag, and by that bind view elements with the model data.
You can simply use
return View();
but if you need to bind data then you have to pass like
return View(model);
for an example
Model Class
public class BookViewModel
{
public Guid Id { get; set; }
public string Name { get; set; }
}
Controller Method
public ActionResult Index()
{
return View();
}
public ActionResult Create()
{
return View(new BookViewModel());
}
View
#using (Html.BeginForm())
{
#Html.HiddenFor(m => m.Id)
<div class="editor-label">
#Html.LabelFor(m => m.Name)
</div>
<div class="editor-field">
#Html.EditorFor(m => m.Name)
#Html.ValidationMessageFor(m => m.Name)
</div>
}
You don't need to pass objects to an action result, although if you don't you can't access the model.
i.e. It is common to do this on static pages such as About screens:
public ActionResult About() {return View();}
Also, it is possible to pass other objects instead of the full model.
See post: Must ASP.NET MVC Controller Methods Return ActionResult?
In Asp.net MVC, View(chtml) is for redering UI;
if your View is simple or static, you can construct your html content in the View without external data.
If you need data (from Db, web service, etc), your View must be able to query the data source.
There are several ways to pass data to view; via the View(Model) statement, via viewbag, etc.
we can also pass service layer object so view can query the datasource by itself.
Why do we need to pass Model to View again? Once in View (cshtml) you cannot access Controller -> you can pass ready to read data or service layer object inside your Model
You can just return a view:
View()
In that view, you won't have a #model you can take data of. You can still pass ViewBag or ViewData to send some dynamic data to the view.
Is it possible to have a View without a model?
YES
Some cases:
Semi static page: You don't need a model because almost everything that will be displayed in the page is static.
Container page: It can contain a lot of partials views, javascript calls or whatever you can imagine to retrieve data dinamically.
Many other cases in which the existence of a Model doesn't correspond to a business logic (or a good practice logic)
Just remember that patrons are there to guide us, not to force us to do things just one way. Check what's best for your application, change the bits that you don't like. Try to take the best of the framework, but remember it is there to help you.
Related
I am new to ASP.NET MVC. Is it possible to pass data from view to model in mvc? this question was asked in interview.Please anyone give me right answer.
Thanks in Advance
To pass data to controller through model you should wrap all the inputs (checkboxes, textboxes, radio etc.) with <form ...> tag. You could do it using HTML tag or with help of ASP.NET MVC helper #Html.BeginForm(...). Once you submit your form, all the input data will be sent to a controller action and mapped to a targeted model. Please see an example:
Model:
public class UserModel
{
public string FirstName { get; set; }
public string LastName { get; set; }
}
View:
#model UserModel
#using (Html.BeginForm("Search", "Events"))
{
#Html.TextBoxFor(m => m.FirstName)
#Html.TextBoxFor(m => m.LastName)
<input type="submit" value="Search" />
}
Controller:
public class EventsController: Controller
{
public ActionResult Search(UserModel model)
{
//do something
return View(); //return "Search" view to the user
//return View(model); //You can also return view with the model to the user
//return View("SpecificView"); //You can specify a concrete view name as well
}
}
No, we do not pass any information from view to model directly, both the view and model are different module. we can pass data, value or any information from view to model via controller.
I am making WCF service call using MyViewRequest view fields inside HttpPost ActionHandler. The goal is to show response using partial view, MyViewResponse
In brief I need to achieve these two items-
Disable load of partial view on first load.
Display Response (along with Request) after service call.
MyViewRequest.cshtml
#using (Html.BeginForm())
{
#Html.ValidationSummary(false)
//html code
}
</div>
<div id="dvResponse">
#Html.Partial("MyViewResponse");
</div>
Partial view: MyViewResponse.cshtml
#model MvcApplication3.Models.MyModel
#{
ViewBag.Title = "MyViewResponse";
}
<h2>MyView</h2>
#Html.Label(Model.MyName, "My Name")
This was pretty straight forward in Asp.Net using userControl, But stuck up here, How can we achieve this in MVC3.
I think the best way is to transfer your data using ViewModels. Let's assume you want to have an app something like stackoverflow where you have a question and user can post an answer and it will be shown after the post along with the question.
public class PostViewModel
{
public int ID { set;get;}
public string Text { set;get;}
public List<PostViewModel> Answers { set;get;}
public string NewAnswer { set;get;}
}
in your GET action, you show the question. Get the id from the url and get the Question details from your service/repositary.
public ActionResult Show(int id)
{
var post=new PostViewModel();
post=yourService.GetQuestionFromID(id);
post.Answers=yourService.GetAnswersFromQuestionID(id);
return View(post);
}
Assuming yourService.GetQuestionFromID method returns an object of PostViewModel with the propety values filled. The data can be fetched from your database or via a WCF service call. It is up to you. Also yourService.GetAnswersFromQuestionID method returns a list of PostViewModel to represent the Answers for that question. You may put both these into a single method called GetQuestionWithAnswers. I wrote 2 methods to make it more clear.
Now in your Show view
#model PostViewModel
#Html.LabelFor(x=>x.Text);
#using(Html.Beginform())
{
#Html.HiddenFor(x=>x.ID);
#Html.TextBoxFor(x=>x.NewAnswer)
<input type="submit" />
}
<h3>Answers</h3>
#if(Model.Answers!=null)
{
#Html.Partial("Responses",Model.Answers)
}
And your Partial view will be strongly typed to a collection of PostViewModel
#model List<PostViewModel>
#foreach(var item in Model)
{
<div> #item.Text </div>
}
Handling the postback is simple (HttpPost)
[HttpPost]
public ActionResult Show(PostViewModel model)
{
if(ModelState.IsValid)
{
//get your data from model.NewAnswer property and save to your data base
//or call WCF method to save it.
//After saving, Let's redirect to the GET action (PRG pattern)
return RedirectToAction("Show",new { #id=model.ID});
}
}
I am new to Asp.net MVC and have no idea as to how can i perform the search. Here's my requirement, please tell me how will you handle this :-
I need to have textbox where user can enter a search query or string. The user then clicks on a button or presses enter to submit it. The string needs to matched with a table's property name.
NOTE:- Querying the data and fetching the result isn't the main point here. All I need to know is how will you take the user input and pass it to a controller action or whatever for further processing. Just tell me how will you read the user input and where will you send it to search.
Asp.Net MVC uses standard HTTP verbs. For the html part, it's a normal html form that points to an url. Server side, that url will be routed to a controller/action which will handle the input and do what is needed.
Let's have a sample. You want to make a search form. First of all, it's a best practice to have search forms use the HTTP GET method instead of POST, so the search results can be bookmarked, linked, indexed, etc. I won't be using Html.BeginForm helper method to make things more clear.
<form method="get" action="#Url.Action("MyAction", "MyController")">
<label for="search">Search</label>
<input type="text" name="search" id="search" />
<button type="submit">Perform search</button>
</form>
That's all the html you need. Now you'll have a controller called "MyController" and the method will be something like this:
[HttpGet]
public ActionResult MyAction(string search)
{
//do whatever you need with the parameter,
//like using it as parameter in Linq to Entities or Linq to Sql, etc.
//Suppose your search result will be put in variable "result".
ViewData.Model = result;
return View();
}
Now the view called "MyAction" will be rendered, and the Model of that view will be your "result". Then you'll display it as you wish.
As always in an ASP.NET MVC application you start by defining a view model which will express the structure and requirements of your view. So far you have talked about a form containing a search input:
public class SearchViewModel
{
[DisplayName("search query *")]
[Required]
public string Query { get; set; }
}
then you write a controller:
public class HomeController : Controller
{
public ActionResult Index()
{
return View(new SearchViewModel());
}
[HttpPost]
public ActionResult Index(SearchViewModel model)
{
if (!ModelState.IsValid)
{
// There was a validation error => redisplay the view so
// that the user can fix it
return View(model);
}
// At this stage we know that the model is valid. The model.Query
// property will contain whatever value the user entered in the input
// So here you could search your datastore and return the results
// You haven't explained under what form you need the results so
// depending on that you could add other property to the view model
// which will store those results and populate it here
return View(model);
}
}
and finally a view:
#model SearchViewModel
#using (Html.BeginForm())
{
#Html.LabelFor(x => x.Query)
#Html.EditorFor(x => x.Query)
#Html.ValidationMessageFor(x => x.Query)
<button type="submit">Search</button>
}
This is the best way to do it.
Create a ViewModel
public class SearchViewModel
{
public string Query { get; set; }
}
Create a Controller
public class SearchController : Controller
{
[HttpPost]
public ActionResult Search(SearchViewModel model)
{
// perform search based on model.Query
// return a View with your Data.
}
}
Create the View
// in your view
#using (Html.BeginForm("Search", "SearchController"))
{
#Html.TextBox("Query")
<input type="submit" value="search" />
}
hope this helps
I'm making an invite system where a user when registering to the site can specify a user who refereed them.
There's also a way for existing users to send invites. The friend would recieve a link:
http://www.foo.com/account/register?referal=sandyUser216
How can I get that value sandyUser216 and place it as the value inside of a text input box?
I'm using C# and MVC3.
Check the Request.QueryString.
<input type="text" value="#Request.QueryString["referal"]" />
Or put it in a Model property rather than having it in the view.
As always in an ASP.NET MVC application you start by writing a view model that will represent the information contained in your view:
public class RegisterViewModel
{
[Required]
public string Referal { get; set; }
}
then you write controller actions for respectively showing the registration form and processing it:
public ActionResult Register(RegisterViewModel model)
{
return View(model);
}
[HttpPost]
[ActionName("Register")]
public ActionResult ProcessRegistration(RegisterViewModel model)
{
if (!ModelState.IsValid)
{
return View(model);
}
// TODO: perform the registration
return RedirectToAction("success");
}
and finally you write the corresponding strongly typed view:
#model RegisterViewModel
#using (Html.BeginForm())
{
#Html.LabelFor(x => x.Referal)
#Html.EditorFor(x => x.Referal)
#Html.ValidationMessageFor(x => x.Referal)
<button type="submit">Register</button>
}
Now all that's left is to simply navigate to /account/register?referal=sandyUser216.
And you have accomplished the whole MVC pattern. Should you skip any of those 3 letters it means that you are doing ASP.NET MVC incorrectly.
So I am new to ASP.NET MVC and I would like to create a view with a text box for each item in a collection. How do I do this, and how do I capture the information when it POSTs back? I have used forms and form elements to build static forms for a model, but never dynamically generated form elements based on a variable size collection.
I want to do something like this in mvc 3:
#foreach (Guest guest in Model.Guests)
{
<div>
First Name:<br />
#Html.TextBoxFor(???) #* I can't do x => x.FirstName here because
the model is of custom type Invite, and the
lambda wants to expose properties for that
type, and not the Guest in the foreach loop. *#
</div>
}
How do I do a text box for each guest? And how do I capture them in the action method that it posts back to?
Thanks for any help.
Definitely a job for an editor template. So in your view you put this single line:
#Html.EditorFor(x => x.Guests)
and inside the corresponding editor template (~/Views/Shared/EditorTemplates/Guest.cshtml)
#model AppName.Models.Guest
<div>
First Name:<br />
#Html.TextBoxFor(x => x.FirstName)
</div>
And that's about all.
Now the following actions will work out of the box:
public ActionResult Index(int id)
{
SomeViewModel model = ...
return View(model);
}
[HttpPost]
public ActionResult Index(SomeViewModel model)
{
if (!ModelState.IsValid)
{
return View(model);
}
// TODO: do something with the model your got from the view
return RedirectToAction("Success");
}
Note that the name of the editor template is important. If the property in your view model is:
public IEnumerable<Guest> Guests { get; set; }
the editor template should be called Guest.cshtml. It will automatically be invoked for each element of the Guests collection and it will take care of properly generating ids and names of your inputs so that when you POST back everything works automatically.
Conclusion: everytime you write a loop (for or foreach) inside an ASP.NET MVC view you should know that you are doing it wrong and that there is a better way.
You can do this:
#for (int i = 0; i < Model.Guests.Count; i++) {
#Html.TextBoxFor(m => m.Guests.ToList()[i].FirstName)
}
There are more examples and details on this post by Haacked.
UPDATE: The controller post action should look like this:
[HttpPost]
public ActionResult Index(Room room)
{
return View();
}
In this example I'm considering that you have a Room class like this:
public class Room
{
public List<Guest> Guests { get; set; }
}
That's all, on the post action, you should have the Guests list correctly populated.