I've got a list of for example Vehicle's that I want to render in a single page, but have different view characteristics for each vehicle type.
Vehicle
- VehicleId
- VehicleTypeId (Car/Boat/Truck/etc...)
- Description
- ...
I'd like to on my main AllVehiclesPage
#foreach(var vehicle in Model) //where Model is a List<Vehicle> from AllVehicles
{
//Render proper View
//CarView(vehicle)
//BoatView(vehicle)
//TruckView(vehicle)
}
In each view it will render differently depending on the vehicle, IE Wheel rim size applies to cars/trucks not to boats etc...
I've read a number of the other questions on Stackoverflow about view inheritance, but they don't seem to apply.
Is this best to do with partial Views? Should I create Usercontrols?
Use display templates. Replace your entire foreach loop with the following line of code:
#model IEnumerable<Vehicle>
...
#Html.DisplayForModel()
And now comes the interesting part. You define display templates for each type that you want to handle:
~/Views/Shared/DisplayTemplates/Car.cshtml
~/Views/Shared/DisplayTemplates/Boat.cshtml
~/Views/Shared/DisplayTemplates/Truck.cshtml
Each template will be strongly typed to the corresponding concrete type. So here's what will happen on the Html.DisplayForModel() line:
ASP.NET MVC sees that the model is an IEnumerable<Vehicle>
ASP.NET MVC starts enumerating over this collection
For each element of the collection ASP.NET MVC looks at its concrete runtime type.
ASP.NET MVC looks for a corresponding display template for this type defined in the ~/Views/Shared/DisplayTemplates folder and automatically renders it by passing this template the current element as model.
You will notice something interesting in this pattern: I use the word ASP.NET MVC very much instead of the word the .NET developer. That's nifty because all that the developer has to do is follow the standard conventions and then ASP.NET MVC will do the job for him so that this developer doesn't need to write loops, doesn't need to write if conditions and doesn't need to reinvent wheels.
Related
I'm starting to develop a new ASP.NET MVC application, and I'd like to make sure that my understanding about the way of developing applications under MVC pattern is correct.
Question 1: Suppose that I have some main views (MainView1, MainView2, ...) with some partial views in it (PartialView1, PartialView2, PartialView3, ...). From what I have understood about MVC, I should define a Model for each view. e.g. I have to define PartialModel, PartialModel2, ... and also define my main models which are containers of the partial models which have been used in them:
public class MainModel1
{
public PartialModel1 Partial1 {get;set}
public PartialModel2 Partial2 {get;set}
public PartialModel3 Partial3 {get;set}
}
This way when I want to redirect to MainView, I can initialize the models used in that view by using this Model. Is my understanding of MVC correct? Or should communication between Views and Models be in another form in MVC?
Question 2: If the above is correct, Then suppose I have a partial view in some of my main view pages. This partial view has a submit button which calls an action method. This action method should somehow return the main page's view with the right viewmodels for views. Is there any recommendation about how to get/set viewmodels of other views in a partial view's action?
Thanks.
You understanding is correct. Each view (no matter whether it is main or partial) should have a corresponding view model (unless in the very rare case where this view contains only static html of course). And following this logic a main view that has to render other partial views will have a view model which itself will have reference (maybe as properties) to view models that are required by those partial views.
There is another technique which is using the Html.Action helper. In this case the partial is rendered through another controller/action than the main one. So you don't need to reference the partial view model in the main view model. They will be completely distinct. Take a look at the following blog post to learn more about Html.Action.
Your understanding is perfectly fine. This is what you can also refer to ViewModel in Asp.net MVC.
So, What basically is an Asp.net MVC ViewModel ?
In ASP.NET MVC, ViewModels allow you to shape multiple entities from one or more data models or sources into a single object, optimized for consumption and rendering by the view. The below image illustrates the concept of a ViewModel:
The purpose of a ViewModel is for the view to have a single object to render, alleviating the need for UI logic code in the view that would otherwise be necessary. This means the only responsibility, or concern, of the view is to render that single ViewModel object, aiding in a cleaner separation of concerns (SoC). Concerns are distinct aspects of the application that have a particular purpose (i.e., concern), and keeping these aspects apart means your application is more organized, and the code more focused. Putting data manipulation code in its own location away from the view and controller, enforces SoC.
Using ViewModels in MVC for finer granularity and better SoC leads to more easily maintainable and testable code. Remember, unit testing is about testing small units.
Along with better coding practices, there are many business reasons demonstrating why you might consider using ViewModels:
Incorporating dropdown lists of lookup data into a related entity
Master-detail records view
Pagination: combining actual data and paging information
Components like a shopping cart or user profile widget
Dashboards, with multiple sources of disparate data
Reports, often with aggregate data
I'm porting an existing system to ASP.NET MVC2. In the current legacy app, the user can select from dozens of available fields to customize CRUD forms for different entities in the domain model, similar to the way ERP systems allow customization of core modules.
My question: I'm looking for a good pattern or example for this kind of behavior in ASP.NET MVC2. It seems to me it's rather like creating a ViewModel dynamically based upon user choices, or perhaps the right approach is data-driven view pages that aren't strongly-typed where I can reflect over the results client-side to determine field headings or something -- if that makes sense :). Or maybe I can drive AutoMapper or similar dynamically # runtime based on user choices?
The underlying domain model is EF4-based and I'm using a simple Repository pattern # present for the ViewModel.
TIA for any input! Michael
If I didn't find anything else that matched the needs and went on to do it custom, I would:
Use the ViewModel with all the fields / not just the ones the user picked.
Pass both the ViewModel and the view configuration to the view
Call some html helper that for each item in the configuration adds a field with the corresponding property in the model
The configuration could be passed as either part of a containing ViewModel or in a separate entry in ViewData
Depending on what you need, building/passing the view configuration could be put in an Action Filter. Alternatively the helper could pull it directly.
A different approach is if you need completely custom fields. I mean user defined fields. If that's the scenario, that's not typed at the controller level already, so I'd pass the list of fields/values to the view. The view can do a foreach on those adding the fields. Again that could be moved to a HtmlHelper.
I am working on a project involves exposing many data entities (more than 200) through an ASP.NET MVC application.
I do not want to write views for every entity mode and I am wondering if there is a way of having one generic view to display different models (for example, a view which reads the model properties(metadata) and generates a HTML table to display a list of entities.
If you only need to display, you can write your own generic renderer in few minutes using reflection. Or, you can use ModelVisualizer from MvcContrib, or Grid from MvcContrib which can do Html.Grid(Model).AutoGenerateColumns() to automatically show properties as columns. It doesn't support DataAnnotations or attributes, but you can write your own extension method that will use reflection to generate Grid's columns based on some attributes. And you can quickly turn this grid into jqGrid using jqGrid's tableToGrid() method.
If you need input support, there're several choices:
MvcContrib's InputBuilder (here you can see a simple example on how it's done with reflection)
MVC v2 InputFor(), I think it supports rendering several properties, but I'm not sure.
My solution does read metadata (attributes) from view models and generates jqGrid formatting and editing options automatically.
There should be commercial tools, too.
Two choices:
Dynamic Data Project
Have you tried Asp.net Dynamic data project that can automagically create what you need?
Asp.net MVC
But if you want to do what you're asking, you can always create a single view that will not have a strong type model. You will always pass data to it ViewData dictionary. The view would then parse that data and display what's required.
Routing
You can always create these two routes:
routes.MapRoute(
"EntityRoute",
"{entityName}",
new {
controller = "Entity",
action = "Display",
entityName = "SomeDefaultEntity" }
);
routes.MapRoute(
"EntityRoute",
"{entityName}/{recordId}",
new {
controller = "Entity",
action = "Details",
entityName = "SomeDefaultEntity",
recordId = string.Empty }
);
that will redirect all requests to the same controller action that will provide correct entity set data and pass it into the ViewData dictionary and return the view that will consume it. The second one will display details of a certain record within some entity (in case you need to provide master/details functionality).
MVC Contrib has Model Visualizer which let you display a Model by reflecting its properties. That a no go if you need any performance at all, but maybe it gets you started.
In Eric Hexter's Input Builders, different templates use different strongly-typed models; for example String uses PropertyViewModel<object>, DateTime uses PropertyViewModel<DateTime>, Form uses PropertyViewModel[], and so forth. Spark View Engine doesn't seem to allow this, because all elements that compose the presentation (masters, views, partials, etc.) are compiled into a single class.
If I try to setup a view involving more than one template, I get the following exception:
Only one viewdata model can be declared. PropertyViewModel<DateTime> != PropertyViewModel<object>
If leave just one viewdata declaration, I get another exception about the passed model item mismatching the required one.
It seems like I will have to give up either the Input Builders or Spark, which is sad because I really love both. So I thought I'd ask here to see if anybody has already figured this out.
Thanks.
You can always use <% Html.RenderPartial() %> for partial view rendering with different model. This will create more than one view class.
I make heavy use of View Components in some of the larger applications I've built in Monorail - What is the equivalent approach in ASP.Net MVC for a view component, that can support sections etc.?
Actually you have several options to create the equivalent of a ViewComponent in ASP.NET MVC, depending in the complexity of your component. I use these two approaches which are the more mvc-ish of the options I am aware of.
1:
The simplest thing is to create a ViewUserControl and display it using Html.RenderPartial with the helper. The ViewUserControl is a simple piece of markup with no backing controller (I think you can put a codebehind file if you want).
Optionally, you can pass a model object or the entire ViewData dictionary to the view when calling RenderPartial, like this:
<% Html.RenderPartial("TopBar", model); %>
"TopBar" is an ascx page. This works anywhere, in master pages and in normal views.
2:
If you want your component to have more complicated logic or to access datasources, IoC, etc, then you can use Html.RenderAction which is an extension method found in the Microsoft.Web.Mvc assembly. I am using this out of the mvccontrib distribution. It works like this, you need to create a normal controller with all the logic you need, then create some views and all of these things become your component, for example:
public class AboutComponentController : Controller {
public IRepository Repository{ get; set; }
public ActionResult Detail() {
var lastEvent = Repository.FindAll<Auditoria>().FirstOrDefault();
return View(lastEvent);
}
}
Notice how I have a reference to an IRepository which is going to be injected with IoC (Windsor in my case) and I can do anything a normal controller would do.
Now, in any page (master or normal) where you want to use your component, import Microsoft.Web.Mvc and call Html.RenderAction with the appropriate parameters. This will create a mini mvc pipeline that creates the controller, resolves the view, etc., just like a Monorail ViewComponent. I prefer to use the lambda based variation of the method, like this:
<% Html.RenderAction<AboutComponentController>(x => x.Detail("a message"));%>
Unfortunately, the only way to pass parameters is to use the method call itself, which in turn must be unique in the controller. Still needs some work to resemble a ViewComponent.
I don't use masterpages or layouts in the views of my components since they are composition elements themselves.
Remember that when using the Webforms view engine, you can have strongly typed views if you like to have intellisense when using the Model variable in code blocks.
The beauty of this is that you can mix view engines with these approaches, I usually create the components in nvelocity and display them in aspx pages, etc.
I now there can be issues with caching of the partial views but I haven't run into any so far. I am sure there are other options (like subcontrollers in mvccontrib) but this is usually enough for simple cases. Of course you can use normal ASP.net components in your aspx view pages but that would be cheating right? hehe. I hope it helps.
Phil Haack blogged about creating areas to group controllers into sub-folders/sections similar to MonoRails.