I'd like to know how to call server side methods from a view page. I need a mean to call directly server side methods whatever I need(not just from a model passed from controller)
<img src="#(pictureService.GetPictureUrl(productId)"/> ...
You will need to pass pictureService from a controller via ViewData or via Model, e.g., extend your Model type to contain that property, or use dynamic models add dynamically add such property in controller.
You could possibly also create static class PictureService and call it like you do ni the sample:
<img src="#(MyNamespace.PictureService.GetPictureUrl(productId)"/>
or
#using MyNamespace;
...
<img src="#(PictureService.GetPictureUrl(productId)"/>
What about using en EmptyResult, or a RedirectResult. You don't have to return something, but doing this lets you run a method server side. You could also use a JSON result, and call it using jQuery, then you could return a boolean to say whether it worked or not.
It's hard to tell from your example code, why you don't just serve the image urls with the page. If your image src is known when you serve the page, why not include it in your view model?
Related
I've spent a couple of hours trying to work out a way to do this. It's such a simple requirement that I can't believe I need to create view models or anything so grandiose.
Very simply, using MVC5, I have a View, let's call it Page1, on which there is a hyperlink. When the user clicks that hyperlink, I want them to be taken to a new View, Page2. On Page2 is an iframe. I want to set the src attribute of that iframe to the URL of Page1, the View that the user was redirected from.
So, if I could maybe use the ViewBag (which people on here don't seem to recommend), to pass the URL of Page1 from that View to the Controller for Page2, and then use Razor in my markup on Page2 to define the src attribute of the iframe, I imagine that'd work fine. Unfortunately, people don't seem to like using ViewBag, and also, I can't find an end-to-end description of how to actually achieve this in code.
Can somebody give me an appropriately straightforward solution to this problem?
A ViewModel for a View can simply be a string - so if you only need to pass a single value in to the view (the URL to use as the src), then in Page2.cshtml, you just define the model at the top like so:
#model string
To use that as the src attribute, you just do e.g.
<iframe src="#Model" .... >
And from the controller, you pass the url string as the model to the view like so:
return View("Page2", myUrlStringVariable);
So, to recap, a ViewModel doesn't necessarily have to be a new class you create - for the most basic scenarios like this, you can just use e.g. a string as the ViewModel. As soon as you start having multiple bits of data to pass in to a View, that's typically when you'd look to create a specific ViewModel class.
Another option may be a JavaScript solution. Something like...
document.getElementById('myIframe').src = document.referrer;
I am starting a new project, and keen to make use of the KnockoutJS + Web Api which are new to me, I have a good understanding of the Web Api, but Knockout is tough to get my head around at the moment.
This is my initial thoughts of how I want my app to work:
I have a standard MVC controller such as LeadsController
LeadsController has an Action called ListLeads, this doesn't actually return any data though, but just returns a view with a template to display data from Knockout.
The ListLeads view calls my api controller LeadsApiController via ajax to get a list of leads to display
The leads data is then mapped to a KnockoutJs ViewModel (I don't want to replicate my view models from server side into JavaScript view models)
I want to use external JavaScript files as much as possible rather than bloating my HTML page full of JavaScript.
I have seen lots of examples but most of them return some initial data on the first page load, rather than via an ajax call.
So my question is, how would create my JavaScript viewModel for Knockout when retrieved from ajax, where the ajax url is created using Url.Content().
Also, what if I need additional computed values on this ViewModel, how would I extend the mapped view model from server side.
If I haven't explained myself well, please let me know what your not sure of and I'll try and update my question to be more explicit.
I think your design is a good idea. In fact, I am developing an application using exactly this design right now!
You don't have to embed the initial data in your page. Instead, when your page loads, create an empty view model, call ko.applyBindings, then start an AJAX call which will populate the view model when it completes:
$(function () {
var viewModel = {
leads: ko.observableArray([]) // empty array for now
};
ko.applyBindings(viewModel);
$.getJSON("/api/Leads", function (data) {
var newLeads = ko.mapping.fromJS(data)(); // convert to view model objects
viewModel.leads(newLeads); // replace the empty array with a populated one
});
});
You'll want to put a "Loading" message somewhere on your page until the AJAX call completes.
To generate the "/api/Leads" URL, use Url.RouteUrl:
<script>
var apiUrl = '#Url.RouteUrl("DefaultApi", new { httproute = "", controller = "Leads" })';
</script>
(That's assuming your API route configured in Global.asax or App_Start\RouteConfig.cs is named "DefaultApi".)
The knockout mapping plugin is used above to convert the AJAX JSON result into a knockout view model. By default, the generated view model will have one observable property for each property in the JSON. To customise this, such as to add additional computed properties, use the knockout mapping plugin's "create" callback.
After getting this far in my application, I found I wanted more meta-data from the server-side view models available to the client-side code, such as which properties are required, and what validations are on each property. In the knockout mapping "create" callbacks, I wanted this information in order to automatically generate additional properties and computed observables in the view models. So, on the server side, I used some MVC framework classes and reflection to inspect the view models and generate some meta-data as JavaScript which gets embeded into the relevant views. On the client side, I have external JavaScript files which hook up the knockout mapping callbacks and generate view models according the meta-data provided in the page. My advice is to start out by writing the knockout view model customisations and other JavaScript by hand in each view, then as you refactor, move generic JavaScript functions out into external files. Each view should end up with only the minimal JavaScript that is specific to that view, at which point you can consider writing some C# to generate that JavaScript from your server-side view model annotations.
For the url issue add this in your _Layout.cshtml in a place where it is before the files that will use it:
<script>
window._appRootUrl = '#Url.Content("~/")';
</script>
Then you can use the window._appRootUrl to compose urls with string concatenation or with the help of a javascript library like URI.js.
As for the additional computed values, you may want to use a knockout computed observable. If that is not possible or you prefer to do it in .Net you should be able to create a property with a getter only, but this won't update when you update other properties on the client if it depends on them.
I'm in serious need of passing url params with View class. Here's code:
if (!ModelState.IsValid)
{
return View(model);
}
This should not only return model based view, but also add specific param to URL (param won't change view details, but is needed as it's one of few automatically generated SessionKeys (one for each tab/window used to view app) and I know no other way to get to it, different than passing as param (it can't be generated everytime, 'cos params will change; it can't be global variable because it'll reset its value each refresh; it can't be static, because static is evul).
Oh this action is called with use of form and submit button, not actionLink or something like this.
EDIT1: I need params to stay in URL after refresh, or I need some other form of keeping data that persists through refresh/validation fail.
If I understand you correctly you have data that you need to use in generating Urls on your page? This just forms part of your ViewModel - or at least it should, since it's data that the View needs in order to render.
You can use ViewData to add any extra data that isn't part of your view model. Or, better still, add the data as members to it. Equally, if different views with different View Models require this data, add a ViewModel base class and derive from that so you can share that data.
use
RedirectToAction("actionName","controller",
new RouteValueDictionary(new {param1="value",param2="value2"});
or you can use hidden field to store the values in your page and then pass this down as and when you need them..
I am building an application using Play for Model and Controller, but using backbone.js, and client side templating. Now, I want the html templates to be served by Play without any backing controller. I know I could put my templates in the public directory, but I would like to use Play's templating engine for putting in the strings in my template from the message file. I do not need any other data, and hence dont want the pain of creating a dummy controller for each template. Can I do this with Play?
You could create a single controller and pass in the template name as a parameter, but I am not sure if it is a good idea.
public static void controller(String templateName) {
// add whatever logic is needed here
renderTemplate("Controller/"+templateName+".html");
}
Then point all your routes to that controller method. Forget about reverse routing, though.
I think I would still rather have a separate controller method for each template. Remember that you can use the #Before annotation (see Play Framework documentation) to have the message string handling in exactly one place, that is executed before each controller method. By using the #With annotation you can even have this logic in a separate class.
You can use template engine from any place in your code:
String result = TemplateLoader.load("Folder/template.html").render(data);
I'm trying to embed a small view snippet that steps through a model fragment that works fine when I embed it in a single controller and pass it to a view like so;
Controller:
return View(_entities.formTemplate.ToList());
View:
http://www.pastie.org/666366
The thing is that I want to be able to embed this particular select box in more than just this single action / view, from the googling I've been doing this appears that it should go into a shared view, but I'm not clear then on how I could populate the model within that view from the controller? (or maybe I'm completely missing the purpose for shared views?)
In the other MVC framework I'm accustomed to working with there is the concept of a filter where you can call code before or after any action and mod the model as it passes the controller and goes to the view, is such a thing possible in .net mvc?
Any assistance appreciated.
You'll want to use the HtmlHelper method DropDownList() in order to create a input:
<%= Html.DropDownList("id", new SelectList(formBuilder, "ID", "Name")) %>
You probably want to use a ViewUserControl here.
You have a couple of options if you go that route. If it's model data that is easily available, recreate it at the call site of your RenderPartial like so:
<%=Html.RenderPartial("ViewName", new ModelData())%>
If it's data that is dependent on the current model data, then you'll need to pass that data somehow to your partial view.
ASP.Net MVC also has the concept of before/after controller actions. You decorate your controller method with an Attribute that derives from ActionFilterAttribute. In there, you have access to OnActionExecuting and OnActionExecuted.