So I have this code:
var list = new List<Carrito> {
new Carrito { ProductId = producto.ID , Cantidad = 1, PrecioUnitario = producto.Precio }
};
Session["list"] = list;
return View();
Then I load the view but I don't know how to print the the content that is inside the session. Any ideas?
This is the code I use inside the view but doesn't work:
#foreach(var item in (IEnumerable<object>)Session["list"] )
{
<p>#item.ProductId</p>
}
it's as simple as reading back the value from your session varable and cast it to the original type, then do whatever you want
example:
#{
if(Session["list"]!= null)
{
var listBackFromSession = (List<Carrito>)Session["list"];
// do what you want
}
}
My recommendation is to use the more elegant way of ViewBag.
a quote from official asp.net mvc website about Viewbag:
New "ViewBag" Property
MVC 2 controllers support a ViewData property that enables you to pass
data to a view template using a late-bound dictionary API. In MVC 3,
you can also use somewhat simpler syntax with the ViewBag property to
accomplish the same purpose. For example, instead of writing
ViewData["Message"]="text", you can write ViewBag.Message="text". You
do not need to define any strongly-typed classes to use the ViewBag
property. Because it is a dynamic property, you can instead just get
or set properties and it will resolve them dynamically at run time.
Internally, ViewBag properties are stored as name/value pairs in the
ViewData dictionary. (Note: in most pre-release versions of MVC 3, the
ViewBag property was named the ViewModel property.)
Further more, This is a good article to read about the different ways you have in MVC in order to preserve data: http://rachelappel.com/when-to-use-viewbag-viewdata-or-tempdata-in-asp.net-mvc-3-applications
example:
var list = new List<Carrito> {
new Carrito { ProductId = producto.ID , Cantidad = 1, PrecioUnitario = producto.Precio }
};
// use ViewBag
ViewBag.myList = list;
then inside your view, read them back like this:
var myList = (List<Carrito>)ViewBag.myList;
// your code
You're doing MVC fundamentally wrong. In MVC, Views are there only to render a model. The logic of accessing that model should be implemented in controller, or in any other place, but not in the View itself.
Thus I recommend that you simply pass your list to the view, and make your view strongly-typed by including #model List<Carrito> at the top.
Related
I am upgrading MVC5 to Asp.Net Core 3 MVC and just found that ModelMetadata.AdditionalValues has been changed to IReadOnlyDictionary. We have stored information in additionalValues before. What is the alternative solution now?
Thanks in advance.
Wilson
What is the alternative solution now?
You could use ViewData and ViewBag to pass data to a view in ASP.NET Core.
ViewData
is a property of the Controller Base class, which returns a ViewDataDictionary object.
The ViewDataDictionary is a dictionary object which allows us to store key-value pairs. The key must be a case-insensitive string. To pass data to the view, you can assign values to the dictionary using the Key. You can store any number of items as needed in the ViewData.
The data stored in the ViewData object exists only during the current request. As soon as the view is generated and sent to the client, the Viewdata object is cleared.
The following is an example that sets values for a Title using ViewData in an action:
1. Codes in Controller
public IActionResult Index()
{
ViewData["Title"] = "Hello World!";
return View();
}
2. Codes in View
#ViewData["Greeting"]
ViewBag
isn't available in Razor Pages. ViewBag is a DynamicViewData object that provides dynamic access to the objects stored in ViewData. ViewBag can be more convenient to work with, since it doesn't require casting. The following example shows how to use ViewBag with the same result as using ViewData above:
1. Codes in Controller
public IActionResult SomeAction()
{
ViewBag.Greeting = "Hello";
return View();
}
2. Codes in View
#ViewBag.Greeting World!
Here you can find more information like below in this link.
ViewData attribute - Another approach that uses the ViewDataDictionary is ViewDataAttribute.
Using ViewData and ViewBag simultaneously
Summary of the differences between ViewData and ViewBag
When to use ViewData or ViewBag
Strongly typed data (ViewModel)
this is my controller
public ActionResult Index()
{
var data = (from o in db.aspnet_Users
from q in db.aspnet_Profile
where
o.UserId == q .UserId
select new{
o.UserId,
o.UserName,
q.Address,
q.Email,
q.Phone,
q.Mobile,
q.SocialID,
}
).ToList();
ViewData["Allprofile"] = data;
return View();
}
and i want to show the data in the view in table, there was a problem to show 2 db Models in one view because the model generated from Database not Code First so i'm trying show the data using ViewData any help ?
why are you not using a ViewModel here? you are somewhat defeating the purpose of MVC.
the view model will encapsulate the data you need to show on the View. you pass the view model to the View - the view will accept the strongly typed view.
the ViewData should never really be used for heavy/complex objects for a number of reasons - performance for one, but also no type safety/strongly typed support either.
change your code so you return a ViewModel with the data you need to show to the user.
i'm looking for a best practices type answer here. basically i have a very chatty application which will be returning bits of data to the client very often. the bits of data returned eventually will end up being html added dynamically to the dom. so i'm trying to choose between the following 2 ways:
return just json data, create the html on the client side using jquery and possibly jquery templates
return the actual html that is build on the server side
i would like to make the choice that is most easily maintained. that is, i want the best way that will allow me to make updates to the html snippets very often.
i'm actually looking for a way to do #2 using ASP MVC partial views and want the ability to use string formatting. essentially i'm looking to make a call like this:
string sHtml = string.Format(GetNewTradeHtml(), "GOOG", "100", "635.50");
and I want GetNewTradeHtml() to actually get the html from a ASP MVC view instead of a string constant that might look like:
const string cNewTradeHtml = "<li><span>Symbol: {0}</span><span>Qty: {1}</span><span>Price: {2}</span></li>";
the string constants seems to be a popular way to do these kinds of things and i hate maintaining those...
basically i think i'm looking for a way to manage view several view templates that i can call ToString() on and get the raw html and use string formatting on it. and i'm hoping there is a suggested way to solve my particular problem natively in ASP MVC (without some hack). but perhaps (unfortunately) the string constants + string.format is the best way to maintain server side dynamic html...
UPDATE:
here's what i've learned since i've posted this question:
there are LOTS of posts here on SO about rendering a view into a string. a lot of different ways, some work with different versions of MVC some don't. some are cleaner than others, some are pretty heavy... ALL of which are normally some type of solution that require a controller context. so in most cases the solutions work great as responses to requests. but for my case, i need to do it outside of the context of a controller so now i need to either mock the controller or make a bunch of fake objects, neither of which i really want to deal with.
so i've determined that there is actually NO easy way to render a razor partial into its string representation without using a controller in a response. they really need to make an easy way to do this without mocking up controller context and request objects.
What are Views in asp.net mvc? They are just html templates, nothing more. They take model and replace template placeholders with model values. And indeed there's no more natural way to render html in asp.net mvc than using Views.
First, declare your view model
public class NewTradeViewModel
{
public string Symbol { get; set; }
public decimal Quantity { get; set; }
public decimal Price { get; set; }
}
than your controller action
public ViewResult GetNewTrade()
{
NewTradeViewModel model = new NewTradeViewModel;
model.Symbol = "GOOG";
model.Quantity = "100";
model.Price = 635.50m;
// PartialView, as you want just html snippets, not full layouts with master pages, etc
return PartialView("TemplateViewName", model);
}
and the very ordinary view - you may have any number of these, just change controller action to return specific one
#model NewTradeViewModel
<li><span>Symbol: #Model.Symbol</span><span>Qty: #Model.Quantity</span><span>Price: #Model.Price</span></li>
Since you mentioned that your app was "chatty" you should probably consider returning Json and rendering on the client side with a template engine.
This is really a toss up though because it looks like your snippets are pretty small.
If you do go with a sending JSON back and forth, I can recommend jquery templates or mustache
backbone.js can also help you better organize your client side components. It is pretty easy to get up and running with it. By default it works with jquery templates, but you can also plug in other templates if you like.
Here is a simple approach to storing templates in separate files, http://encosia.com/using-external-templates-with-jquery-templates/
ijjo,
Just looked at your question again and notice that you are referring to returning the html partialview as a string. there are loads of references here on SO to this type od function, but below is my version taken from an 'old' mvc app that's still in production. without further ado, it's an extension method that hooks into the controller:
public static class ExtensionMethods
{
public static string RenderPartialToString(this ControllerBase controller, string partialName, object model)
{
var vd = new ViewDataDictionary(controller.ViewData);
var vp = new ViewPage
{
ViewData = vd,
ViewContext = new ViewContext(),
Url = new UrlHelper(controller.ControllerContext.RequestContext)
};
ViewEngineResult result = ViewEngines
.Engines
.FindPartialView(controller.ControllerContext, partialName);
if (result.View == null)
{
throw new InvalidOperationException(
string.Format("The partial view '{0}' could not be found", partialName));
}
var partialPath = ((WebFormView)result.View).ViewPath;
vp.ViewData.Model = model;
Control control = vp.LoadControl(partialPath);
vp.Controls.Add(control);
var sb = new StringBuilder();
using (var sw = new StringWriter(sb))
{
using (var tw = new HtmlTextWriter(sw))
{
vp.RenderControl(tw);
}
}
return sb.ToString();
}
}
usage (as per archil's example above):
public ViewResult GetNewTrade()
{
NewTradeViewModel model = new NewTradeViewModel;
model.Symbol = "GOOG";
model.Quantity = "100";
model.Price = 635.50m;
// PartialView, as you want just html snippets, not full layouts with master pages, etc
return this.RenderPartialToString("TemplateViewName", model);
}
good luck and enjoy...
I am just new to MVC.
when we use "#Html.EditorFor" in razor view, it generates textbox.
My requirement is that I need to supply some value from viewbag or session to user's in that textbox?
Is it possible and if yes how can i do?
OR
What are the alternatives?
In your action method in the controller, pre-load a model with some data:
public ActionResult Index()
{
MyModel model = new MyModel();
model.FirstName = "Bob";
model.LastName = "Hoskins";
return View(model);
}
Then make your View strongly typed. These pre-set values should now appear on your view. You probably want to populate them from a service layer or resource file, rather than have them as hardcoded strings like my example.
I'n new at this, so apologies if this isn't explanatory enough. I want to prepopulate a field in a form in asp.net mvc 3. This works;
#Html.TextBox("CompName", null, new { #value = ViewBag.CompName })
But when I want to prepopulate it with a value and send that value to my model, like this;
#Html.TextBoxFor(model => model.Comps.CompName, null, new { #value = ViewBag.CompName })
It won't work. Any ideas?
Thanks in advance!
So, I would suggest is to move to using viewmodels rather than the ViewBag. I made a folder in my project called ViewModels and then under there make some subfolders as appropriate where I put my various viewmodels.
If you create a viewmodel class like so:
public class MyViewModel
{
public string CompName { get; set; }
}
then in your controller action you can create one of those and populate it, maybe from some existing model pulled from a database. By setting that CompName property in the viewmodel, it'll have that value in your view. And then your view can look something like this:
#model MyNamespace.ViewModels.MyViewModel
#Html.EditorFor(model => model.CompName)
or #Html.TextBoxFor would work too.
Then back in your controller action on the post, you've got something like this:
[HttpPost]
public ActionResult MyAction(MyViewModel viewModel)
{
...
// do whatever you want with viewModel.CompName here, like persist it back
// to the DB
...
}
Might be that you use something like automapper to map your models and viewmodels but you could certainly do that manually as well, though the whole lefthand/righthand thing gets quite tedious.
Makes things much easier if you do it this way and isn't much work at all.
Update
But, if you really want to pass that value in view the ViewBag, you could do this:
In your controller action:
ViewBag.CompName = "Some Name";
Then in your view:
#Html.TextBoxFor(model =>model.Comps.CompName, new {#Value = ViewBag.CompName})
And that'll pre-populate the textbox with "Some Name".
I'd still go with the viewmodel approach, but this seems to work well enough. Hope that helps!
From your controller, if you pass a model initialized with default values using one of the View(...) method overloads that accepts a model object, these values will be used by the view when rendered. You won't need to use the #value = ... syntax.