I'm working on a ASP.NET MVC 3 application, but I'm rather new to MVC in general.
I have a partial view in a my application layout view that needs to have data passed to it. this will appear on every page. Is there a way to make this happen so I don't have to load that data into the view model for every action in the entire site?
As in, if a user navigates to Mysite/admin/settings, I would like to have the partial view on the layout be able to somehow receive the data that it needs without me needing to put that code in the Settings action in the Admin controller.
On this same note, how do you pass data to the layout view of an application anyway?
In these situations I usually use a base ViewModel for my Views
public class ApplicationViewModel
{
public string UserName {get; set;}
....
}
public class SettingsViewModel : ApplicationViewModel
{
}
all your views would inherit from that ViewModel. Your layout would expect it as well
_layout.cshtml:
#model ApplicationViewModel
....
<h1>hello #Model.UserName</h1>
hopefully this answers your question
Partial only renders a view. You need to provide the model manually.
You can create an action for the view you want and render it with Html.Action( actionName ).
Make an action for example menu which will create a model that will be provided to the menu view.
Now you can call the #Html.Action("menu") from wherever, and it will be rendered autonomously. (you can ofcourse provide a controller name as well, and even custom routeData)
You might also want to set Layout = null; in the view to avoid using the master layout of the whole site.
This is how I pass a value to the partial view from my layout page:
Layout page code:
Html.RenderPartial("_SubMenuLeft", new ViewDataDictionary { {"category", "MMG"} });
and in my _SubMenuLeft.cshtml (partial view)
#if (ViewData["category"] == "MMG")
{
...
}
Hope it helps someone for future reference.
Related
I am new to ASP.NET Core and have some trouble with binding global models and viewmodels to razor views. My application is a mixture of Web API and MVC with razor views.
My goal
When I open an ASP.NET MVC page, I need to instantiate a model by loading it from the database (DbContext service) based on an id received in a cookie. I want to use this model object globally in every view or partial view.
Current Implementation
I can access the cookies in action methods of page controllers, so that I have to load the model from the DbContext in every action method and bind it as viewmodel to target view. This is not practical, because I have to do this in every page controller, because I need that model object on all pages in my navigation pane.
Idea
I think it should be possible to access to Cookies and dbcontext within Startup.cs and bind the model object to _ViewStart.cshtml, so that it is accessible globally in every view or partial view. Even this approach were correct, I do not have any idea how the code would look like. Because I am learning Web-Apps with .NET Core by learning by doing and try and error at the moment. :(
UPDATE
I have a layout page _Layout.cshtml, which includes partial views like the _NavPane.cshtml. My goal is to pass a Model object to the _Layout, which is instantiated via loading from the database (I have a service IMandantRepository for this purpose) and dependent on a cookie.
That model object is needed on every page request. That's why it would be a better practice to load the model object outside the MVC page controllers and pass it to them (what I can not implement technically).
I tried to find a solution by myself and ended up in following interim ugly solution. Following is the content of the _ViewStart file. On the bottom I assign the needed global variables, which I can use in every view or partial view.
This solution has at least two disadvantages:
The model object is possibly loaded redundantly.
Too many program logic in a view file.
#inject MyProject.Data.IMandantRepository mandantRepo
#{
// Main layout template
Layout = "_Layout";
// Define default values
bool showAdminSection = false;
string src = "/images/logos/nologo.png";
// Read cookie value
string currentMandantUid;
Context.Request.Cookies.TryGetValue("currentMandant", out currentMandantUid);
// Load mandant from the database
var thisMandant = mandantRepo.GetMandantByUid(currentMandantUid);
if(thisMandant is Mandant){
src = "data:image/*;base64," + thisMandant.GetBase64Logo();
showAdminSection = thisMandant.Abbr == "AdminMandant";
}
// Assing global variables to ViewData
ViewData["CurrentMandant"] = thisMandant;
ViewData["logoSrc"] = src;
ViewData["showAdminSection"] = showAdminSection;
}
This is an example code in ConfigureService() of Startup.cs. You can register your dbContext class in this way.
services.AddDbContext<BookStoreContext>( options =>
options.UseSqlServer(_configuration.GetConnectionString("DefaultConnection")));
I'm new with ASP.Net Core (3.0 in this case) and I´m trying to create a menu that is visible on all views of a WebApplication, is created dynamically and must be populated only once. Below i explain the steps and try outs i did to reach the goal needed (if required i can share the code I'm using).
This is what i did:
In a simple way, using the "_Layout.cshtml" page, i created a static HTML menu and made all other views simply inherit that layout. So far, so good;
Next challenge comes from the fact that the menu items are dynamically created after a User has logged-in, which i managed to overcome by setting a ModelView inside a controller (HomeController.cs with Index action in this case), and then delivering it to the view. For this case works OK, because the default page is ~\Home\Index\, problem is when i change to a different view with a different controller, the menu has to be rendered again, and so i have to replicate the code (a problem dealt create a BaseController and BaseModel based on this post along side the OnActionExecuted to host the menu generating code)
Now, the biggest problem is the fact that i can only populate the menu once, after the user logs-in. Each time there is a redirect between different controllers/views (post-back of same controller/view works fine), the model is null inside the OnActionExecuted, I tried using ViewData, ViewBag, TemData, but all are null.
So, my question is, how to keep that specific data alive and shared, basically across all the views, and only gets populated once (after each user login) between redirects from different views?
I have been reading around and found several solutions besides the one i did, but i did not found any that could keep data alive throughout the user session the way I need:
ViewBag, ViewData and TempData
Can the shared layout view have a controller in ASP.NET MVC?
Pass data to layout that are common to all pages
To sum up, my flow at this moment, is like this:
User Logged-in
Redirect to default: ~\Home\Index
MenuModelView.cs for the menu gets built and HomeController.cs returns to Index.cshtml with the model attached to it.
Index.cshtml receives the populated ModelView and it uses _Layout.cshtml
The _Layout.cshtml builds the HTML tags for the menu based on the MenuModelView.cs data
User navigates to a different view and steps 3 to 5 are repeated from a specific controller/view
If you want to create a control that can be accessible in all pages without changing every controller, I strongly suggest creating a view component. For a view component has no relationship with your controller, but can access dependencies like database and full HTTP context.
For example, you want to build a custom nav menu, you can just create a view component named NavHeader
using Microsoft.AspNetCore.Mvc;
namespace YourProject.Views.Shared.Components.NavHeader
{
public class NavHeader : ViewComponent
{
public NavHeader(YourDbContext context)
{
// you can access your dependencies, like database.
}
public IViewComponentResult Invoke()
{
// your own logic. You can access HTTPContext here.
var model = new YourOwnModel();
return View(model);
}
}
}
And just call it in any view or layout.
<!DOCTYPE html>
<html>
<head>
<title>Example</title>
</head>
<body>
#*Render your component like this*#
<vc:nav-header></vc:nav-header>
</body>
For more details about view component, please reference:
https://learn.microsoft.com/en-us/aspnet/core/mvc/views/view-components?view=aspnetcore-3.1
https://anduin.aiursoft.com/post/2020/1/4/share-view-component-between-different-aspnet-core-web-project
I have got asp.net mvc 3 website, I want to add feedback feature to all pages.
I created the partial view for this purpose and render it in master layout.
#model FeedbackHelper
Name:<br />
#Html.TextBoxFor(o=>Model.Name)
for example in Questions page , MVC returns the exception because that page binded the POST entity, as far as I check in StackOverflow I have got 2 solution
create a parent model and add POST and FeedbackHelper as properties
use Tuple
at the moment, changing all models is too risky for me.
Is there any good solution ?!
You could use child actions. The idea is to define a specific controller action that will serve the partial view and then include it using the #Html.Action helper in your Layout.
So:
public ActionResult Feedback()
{
FeedbackHelper model = ...
return PartialView(model);
}
then you will of course have a partial in the Shared folder:
#model FeedbackHelper
Name:<br />
#Html.TextBoxFor(o => o.Name)
and include it in your Layout:
#Html.Action("Feedback", "ControllerContainingTheFeedbackAction")
I have a C#.Net web app and I am trying to access one of the HTML/ASP Text Boxes in the Controller for the Edit View of my Proposal model. In a non-MVC app, I was able to do this using Control.ControlCollection.Find(). Is there an equivalent for a MVC3 project?
You ask for an equivalent of Control.ControlCollection.Find() in MVC?
In MVC your controller is not aware of controls.
The controller just receives data via parameters and returns data via the function result.
What do you want to do with the control in your controller code?
If you want to access the value, you should bind it to a parameter:
View:
<input name="MyControl" type="text" />
Controller:
public ActionResult MyAction(string MyControl) {
// MyControl contains the value of the input with name MyControl
}
The MVC pattern was designed to keep things separated.
The View has no knowledge of the controller at all
The Controller only knows that a view exists and what kind of data that it needs. It do not know how the data is render.
Hence, you can never get information about controls/tags in the view from the controller. You need to use javascript/jQuery in the view and invoke the proper action in the controller.
In an MVC-application you don't have controls like in a webform-application.
In MVC you collect your required data in the controller and pass it to the view.
Typicaly the view is a HTML-page with embedded code.
In opposite to controls in webforms which produce HTML and handles the post-backs in MVC you have to do all this manually. So you don't have controls with properties and events wich you can access easily in the controller and you have to handle all your posts with your own code.
Thats sounds as it is a lot of more work - and indeed it could be if you implement the behaviour of complex controls - but MVC applications are much better to maintain and you have 100% influence to the produced HTML.
Well probably i am late for this but it should help others in future...u can store ur value in hidden field in view and then access that value in controller by following code..
Request.Form["hfAnswerOrder"].ToString();
Point - hfAnswerOrder is the ID of the hidden field
My Control in cshtml page..
#Html.Hidden("hfAnswerOrder", Model.Answers.ToList()[0].AnswerOrder)
Using ASP.NET MVC3 I created a new Razor view and gave it the same name as the existing .aspx view that I had been using. I noticed that controller continued to pick up the .aspx view (which has the same name as the action) which is pretty much what I expected. I then renamed the .aspx view and action picked up the razor .cshtml view.
So if I have two views called myview.aspx and myview.cshtml and an Action called MyView() that does a return View(), it will pick up the myview.aspx view and return that.
How does MVC3 decided which view-type to default to?
Is there a way to change this default behavior to prefer a razor view over an .aspx view?
Everything stems down to the order of view engines in the ViewEngines.Engines collection. Here's how the ViewEngines static constructor looks like (as seen with Reflector in ASP.NET MVC 3 RTM):
static ViewEngines()
{
ViewEngineCollection engines = new ViewEngineCollection();
engines.Add(new WebFormViewEngine());
engines.Add(new RazorViewEngine());
_engines = engines;
}
which explains why WebForms is the preferred view engine.
So you could perform the following grotesque hack in Application_Start to inverse the preference towards Razor :-)
var aspxVe = ViewEngines.Engines[0];
var razorVe = ViewEngines.Engines[1];
ViewEngines.Engines.Clear();
ViewEngines.Engines.Add(razorVe);
ViewEngines.Engines.Add(aspxVe);
I would imagine its down to the order in which view engines are registered. Earlier registered view engines will be queried first. If you want to change the order:
ViewEngines.Engines.Insert(0, ...);