I have a partial view that I want to be generic. According to this question, partial views cannot be generic. So I instead made an HtmlHelper extension that handles the pieces for which I want type-safety, then hands off the rest to a real partial view.
Usually my helper is called on page load, which works fine, but sometimes I want to add a row or something through AJAX. When this happens, the controller cannot use my "partial view" since it does not have access to the HtmlHelper.
Apart from having a partial view with a model of type object, is there anything I can do?
I'm using Razor, if that is important.
A simplified version of what I'm doing:
public static MvcHtmlString DoStuff<T>(this HtmlHelper html, IEnumerable<T> data,
Func<T, ViewModelType> StronglyTypedFn, string PartialName)
{
// the pre- and post-processing for the partial view is complex enough I'd like
// to encapsulate it. But I want the encapsulation to include the safety
// benefits that generics give.
var mappedData = data.Select(StronglyTypedFn);
string htmlData = "";
foreach(var model in mappedData){
htmlData += html.Partial(PartialName, model);
}
htmlData += "some boilerplate footer html";
return htmlData;
}
I realize that in this example I have so few lines of code outside the partial view that it seems pointless to have a helper, but in my real example it is more complex.
Now, in an ajax call I want to return Html.DoStuff(). But I can't, because this requires access to the HtmlHelper, and the helper isn't available inside a controller.
You could just have a simple action method that calls the partial for one model instance
public PartialViewResult Single(string partialName) {
return PartialView(partialName);
}
You could use a View with a Dynamic type instead of object.
But... It seems as if there's some misunderstanding here because the Controller shouldn't try to render the view at all. Could you post the Controller code?
The better option is, IMO, returning a JsonResult for your ajax request and adding the row/rows on client side using JS.
Related
Is there a way by which I can do somethin like this inside a Razor view:
<h1>Normal razor code</h2>
#Html.Action("NormalRazorCode")
#Eval(" #Html.Action(\"RuntimeEval\") ")
Basically a text-to-razor compiler at runtime (that doesnt create a whole new view like RazorEngine does for example).
I think you could assume that the views exist at compile time, and create the actual files at runtime, this way the ViewEngine will work the way it does by default
basically you could create a Html.Eval helper that will create the .cshtml file and after Render it using Html.Action or Html.Partial
I wanted to do something similar; I have model data (under my control) stored in a database, and it would simplify my life if I was able to include HTML helpers in those strings that could be "expanded" when included in a page.
Main motivation was to allow me to re-use existing partial views.
There's no eval function, but you can easily write an extension method that will evaluate methods that you choose to allow in advance. In my case, I want to evaluate calls to #Html.Partial(). The example here is pretty simple - it looks specifically for #Html.Partial("somePartialView") calls and replaces it with the actual partial:
public static IHtmlString ExpandHtmlString(
this HtmlHelper htmlHelper,
String html)
{
if (String.IsNullOrEmpty(html))
return new HtmlString(html);
const String IDENTIFY_PARTIAL = #"#Html.Partial\(""([a-zA-Z0-9\-_]*)""\)";
var partialFinder = new Regex(IDENTIFY_PARTIAL);
var matches = partialFinder.Matches(html);
foreach (Match m in matches) {
var matchedStr = m.Value;
var viewName = m.Groups[1].Value;
var partial = htmlHelper.Partial(viewName);
html = html.Replace(matchedStr, partial.ToHtmlString());
}
return new HtmlString(html);
}
And you call it from your Razor page as so:
#Html.ExpandHtmlString((String)Model.SomeStringField)
You could easily expand on this to to evaluate a set of methods or operators that you decide in advance you will accept.
I have one page that will contain a lot data.
Outline of the page is on the image.
For output I have used "razor" engine.
Now I wonder will I get something if I refactor my code so each section
which data comes from database will be partial view?
On this page I need about 20 value objects to display all needed data.
I have made one "ViewModel" class that contains all data I need and set that
viewModel class as razor page model. Is this the right way how I should do this or
there is some smarter way?
public class MyViewModelClass{
public ValueObjectx x;
public ValueObjecty y;
public ValueObjectz z;
public List<ValueObjectT> tList;
public List<ValueObjectG> gList;
public List<ValueObjectS> sList;
}
In a scenario like this I would typically have each section as a partial view. Each section is responsible for it's own layout and ViewModel. This prevents the tendency to have a super view which has to know about too many things in order to render.
I would not use one ViewModel for all the data. I would only use the ViewModel for the data that might actually be posted back to the server. For all the other data, like lists, I would put it on the ViewBag. Like:
public ViewResult SomeAction()
{
var model = GetYourModelData();
ViewBag.TList = GetTList();
ViewBag.GList = GetGList();
ViewBag.SList = SList();
return View(model);
}
You could put all the lists in a separate helper object if you use them a lot.
Note that this is not a "this is how you should do it answer", it is more a description of what works for me. But as I see it the model of the view is one thing and the actual data, as data in drop downs etc., on the view is another thing and should be put in the ViewData property, but the ViewBag is just a dynamic wrapper around the ViewData property. You can then use the properties on the ViewBag as input to your partial views that should make up each of your sections.
I have a large view that needs some conditional logic to decide which of several html chunks to render in the middle of the view. I have a property on my model which can have several different values which determines the html to be output.
I would normally put conditional logic in an html helper, but given that each output is a fair chunk of html, I am not sure that escaping these in a c# file would be great. I could also put the logic in the action and render different views but given that the majority of the view is the same, this does not seem great either. So I am left with multiple if statements in my view (or partial?) which also seems ugly (and is obviously untestable).
What is the best way of doing this?
(I am using MVC3 in case there is something new and funky I can use!)
I usually put separate visual chunks in their own partials. Then my view conditionally calls each partial with Html.Partial. This keeps you main view from bloating.
In general, I try to avoid Html.Helpers that contain more than a single element.
Something like:
#if(Model.HasA)
{
#Html.Partial("widgetdetails-hasa")
}
#if(Model.HasB)
{
#Html.Partial("widgetdetails-hasb")
}
// etc
IMHO logic like this is fine for a view:
#if (Model.ShouldShowSomeSection)
{
... some large chunk of HTML
}
else
{
... some alternative
}
I agree with the answer from #bmancini , but here's what I'd do slightly differently:
I would logically group those 'several html chunks to render' into different partial views :
_partialViewA.cshtml and _partialViewB.cshtml
I then would use extension methods and have my logic in a Helpers folder, then Html sub-folder like this:
using System.Web.Mvc.Html;
public static class SomeViewHelper
{
public static MvcHtmlString OutputHtmlString(this HtmlHelper helper , SomeModel model)
{
if(model.HasA)
{
return helper.Partial("_partialViewA", model)
}
if(model.HasB)
{
return helper.Partial("_partialViewB", model)
}
}
}
This would remove all the logic from the view which would now only have this code:
#Html.OutputHtmlString(Model);
At least this would remove the 'ugliness' and avoid the conditional statements, and also avoid 'escaping the html chinks in C# code'...
Of course I would have to reference the Helpers.Html folder with a #using statement in the view.
Is it possible to detect a route value in a view?
Such as /pages/create/1 and I want to check to see if 1 is there?
Basically, I want to render a different partial view based on this value though I'm fairly sure this is probably not the best way to go about what I'm trying to achieve.
On a side note, instead of doing the above is it possible for me to be able to change what partial views are rendered in a view based on a value from within my controller?
ViewContext.RouteData.Values["whatever"]
You can inspect a RouteData object through ViewPage.ViewContext.RouteData. Then check for values using something like
string areaname = routeData.Values["area"] as string;
string controllername = routeData.Values["controller"] as string;
string actionname = routeData.Values["action"] as string;
string id = routeData.Values["id"] as string;
If you find that you want to inspect these values in the controller instead, you can access them using ControllerBase.ControllerContext.RouteData. Something similar applies for action filters etc.
Other answers are correct, but thought i'd address your last sentence:
On a side note, instead of doing the above is it possible for me to be able to change what partial views are rendered in a view based on a value from within my controller?
Well partial view's are rendered in the View itself (unless calling from JavaScript and binding directly to DOM) with the following code:
<%: Html.RenderPartial("SomePartial") %>
So to prevent "code soup" (if statements) in your view, you use a HTML helper which calls through to RenderPartial after inspecting the ViewContext:
public static string RenderCustomPartial(this HtmlHelper helper, RouteData rd)
{
string partialName;
if (rd.Values["SomeParam"] == 1)
partialName = "PartialOneName";
else
partialName = "PartialTwoName";
return helper.RenderPartial(partialName);
}
And then in the View:
<%: Html.RenderCustomPartial(ViewContext.RouteData) %>
You could make some mods to the above - like access the route data directly in the extension, pass through the model to bind in the partial, etc - but you get the idea.
Alternatively you could do the above IF statement in your controller, and stuff the partial view name in the ViewData, then use that in the regular RenderPartial call in your View.
Whatever floats your boat. :)
A function returns only one view.
what if I want to return multiple views in a function?
For example, I have this code:
Function Index() As ActionResult
Dim _news As DataTable = News.newsSelect()
Dim _announcement As DataTable = Announcement.SelectAnnouncement()
Return View()
End Function
I want to return _news and _announcement to be used in the aspx page. How would I do this?
Are you trying to show both sets at the same time? News and Announcements?
If so then why not implement either a PartialView or two PartialViews?
Then in your main view you can render them and pass the collection to the PartialViews?
There are heaps of samples on this and the one I recommend is in NerdDinner if you haven't already seen it.
I hope this helps. If you want sample code then let me know.
One simple way is just to have those two datasets sent in a ViewData element, which you can access in a field.
example:
ViewData["Elements"] = new SelectList(aElements, "Guid", "Name");
is consumed as:
<%= Html.DropDownList("Elements","Pick an element")%>
Also, I think that if you read between the lines of this blog post here you will find an elegant way of achieving what you want ;) but its a bit more involved..(only because you mentioned Views instead of just variables..
Quote:
We need to create our own implementation of IViewFactory. This
is responsible for locating and
creating an instance of an IView
(which both ViewPage and
ViewUserControl implement).
To “inject” (all you DI fans excuse me borrowing the term without
using a DI framework) our new View
Factory into every Controller we are
going to create our own
IControllerFactory implementation.
We need to configure the framework to use our new Controller
Factory.
Finally we can create two Views – an AJAX version and a pure
HTML version.
Building on that should be all you need
Good luck!
Ric
Assuming what you are trying to do is use both of those DataTables to populate some View, then my recommendation would be to create a wrapper object and then a strongly typed view based on this object.
The wrapper object would contain properties for all of the data elements that you need in order to render your view properly. In your case, it is 2 DataTable objects. I do not really know VB, so all my examples will be in C#. Here is an example of the data wrapper class...
public class IndexViewData
{
public DataTable News { get; set; }
public DataTable Announcement { get; set; }
}
You then might update the Index action in your controller as follows:
public ActionResult Index()
{
var viewData = new IndexViewData();
viewData.News = News.newsSelect();
viewData.Announcement = Announcement.SelectAnouncement();
return View(viewData);
}
Finally, you would need to create/update your view to be strongly typed. This is done by having your page inherit from the generic System.Web.Mvc.ViewPage<T> class. Just substitute the view data wrapper created earlier for T. To do this, you would set the inherits attribute of the <%# Page %> element. In your case, if we assume your root namespace is called "Foo", you might have the following page declaration in your Index.aspx view (added extra line breaks for readability):
<%# Page Title=""
Language="C#"
MasterPageFile="~/Views/Shared/Site.Master"
Inherits="System.Web.Mvc.ViewPage<Foo.Models.MyModelType.IndexViewData>"
%>
Once you have a strongly typed view for your view data wrapper, you can access the wrapper object in your view using the Model property. Here is an example of something you could do in your Index.aspx view
<%-- Output some random data (bad example, for demonstration only) --%>
<%= Model.News[0]["title"] %><br/>
<%= Model.Anouncement[0]["body"] %>
In reality you're probably going to do something like iterate over each row of the data table. Regardless, once you create the strongly typed view, your model object, which was passed to the view in the Index method of the controller, is available in the Model property within the view.
You can find detailed tutorials at the ASP.NET MVC site