What is the point of Partial Views in Asp.net MVC - c#

Ive noticed that there seems to be no real difference between a view and a partial view.
For instance, one can create a view but can render it as a partial view by using
#Html.Partial("ViewName")
or by specifying that its action return it as
return PartialView();
Ive noticed that the opposite is also the case - ie, one can create a partial view but if it is returned as a full view, it will be displayed with the default layout for the views.
My question is this -
When adding a new view in Visual Studio, one is given the option of creating a view that is partial or not. Isn't this redundant, since a view can be rendered as both a partial and a full view anyway?

There is difference between views and partial views, and the difference is more about their usage, rather than technical.
View is meant to be used as full page of your application, it needs layout, <html> and <title>. Partial views are more like reusable parts of other views. Partials do not represent full pages, they are inserted into other views.
From technical point of view, return View("SameView"); renders view including layout page, and returning that same view by return PartialView("SameView"); renders contents, but omits contents of layout page.

No difference - it's true. But when you say "Partial View" all your teammates understand that you mean reusable views that will be used in many places across the website.

Think of partial views as user controls in ASP.NET WebForms. Partial views are used if you want to have a functionality centralized, so it can be used in many parts of your website. This is the purpose of partial views.
Hope I have answered your question.

Two things. First, to an extent you are right. But it's more of a semantic thing to seperate reusable code. It also comes in handy when for e.g. say you need to display a dialog but only when the user has some sort of an interaction with the page, like the click of a button. With partial views you don't have to have the markup for this on the page when it loads thereby reducing the file size. When you write markup/code in the partial view, you don't have to do the whole <html></html> code block. Instead you just create a <div></div> or whatever you need.
The bit about creating a view in Visual Studio. No, it's not redundant because when you create a partial view, it does not use your master layout file.

Practically , there is no difference among them. But when you acknowledge an html object as Partial View then, it is considered as a self-contained object which may get serve at different places just like a web-part/User-Controls and also its lightweight.

Partial view kept to use as partial page of the main page(parent page).
What does mean of partial view? Actually in the main page we will have all the HTML page attributes as below:
html lang="en"
head
title
meta
body
But in partial view we will not have all above attributes.
Find the features of partial page:
1. Partial page will be light wait and get fitted into the any view.
2. This will use as the reusable component.
3. Partial view will be render inside of a View(parent view or page).
For all who coming from ASP.Net background they can understand partial view as user control.
Thanks
Afazal
mdafazal#gmail.com

To answer your question specifically, when adding a new view in Visual Studio, you will get some very basic markup generated for you as a starting point, based off of your selections in the dialog.
Here is the generated markup in Visual Studio 2010 (VB.NET) for the different combinations of the "Partial" checkbox and the "Layout" checkbox:
# "Create as a partial view" unchecked
# "Use a layout or master page:" unchecked
#Code
Layout = Nothing
End Code
<!DOCTYPE html>
<html>
<head runat="server">
<meta name="viewport" content="width=device-width" />
<title>MyView</title>
</head>
<body>
<div>
</div>
</body>
</html>
# "Create as a partial view" unchecked
# "Use a layout or master page:" checked
#Code
ViewData("Title") = "MyView"
Layout = "~/ThePath/ToThe/Layout.vbhtml"
End Code
<h2>MyView</h2>
# "Create as a partial view" checked
# "Use a layout or master page:" greyed out
# returns an empty file
As you can see there is nothing fancy going on in the background or special properties being set in a secret file somewhere. The options are simply used to get some default markup on the page. Whether or not this is practical is purely subjective!

Quite late but might be useful for someone with the same question. Partial views are helpful in a scenario where you want to load a view based on some user selection.
For instance, let's assume there is a dropdown in parent view displaying three operations that the user can perform. Based on the user selection, a partial view can be loaded into the parent view instead of keeping hidden DIVs in the parent view itself, thus making the parent view light. This will be very useful when we have multiple such user selections based DIVs

Related

How to pass a section to a partial in layout?

In ASP.net MVC 5 We can pass section to layout using
#section AnySection{
//section code here
}
and render it in Layout by
#RenderSection("AnySection", required: false)
But how can we pass that section again to a partial inside that layout? See the image below for reference
subheader-v1 is a partial view inside my Layout I have made my Layout with many partial Views.
When I try this as mentioned in Image above it gives me this error
The file "~/Views/Shared/partials/_subheader/subheader-v1.cshtml" cannot be requested directly because it calls the "RenderSection" method.'
You don't pass a section to the layout. It is the layout that determines which sections should (or could) be rendered in the view... it also determines where in the view the section should be rendered.
From MS Documentation:
A layout can optionally reference one or more sections, by calling
RenderSection. Sections provide a way to organize where certain page
elements should be placed.
Sections don't work in partial views and that is by design. You would need to move RenderSection to your layout and the section body to your view. See this question for more information.
Inside the subheader-v1.cshtml (since the objective is to bring the "CoordinatesSelection" partial into subheader-v1.cshtml) substitute
#RenderSection("Coordinates", required: false)
FOR
#Html.Partial("CoordinatesSelection", Model)
The code #RenderSection("Coordinates", required: false) was designed to be written directly in the layout to avoid duplicate calls to it!!
Two ways:
1.
You can migrate from subheader-v1 to layout
layout:
// your subheader-v1 code
#RenderBody()
And you can use RenderSection in the layout
2.
You can pass a model to Partial subheader-v1
*layout:
#Html.Partial("partials/_subheader/subheader-v1",RenderSection("Coordinates",false))
#RenderBody()
*subheader-v1:
#model object
.
.
.
<div class="kt-subheader__wrapper">
#Html.Raw(Model)
*SelectClosetStore
#section Coordinates{
//your partial code
}
I think the first way is better than the second way.

Comparison between Layout and partial view within Asp.net mvc application

I have an Asp.net Mvc4 application which contains 4 modules. I need to add Layouts view (master page) to my project and i have two choices :
Adding 5 Layouts with no partial view
Adding a unique Layout with 4 partial views
I'd like to know what is the best way between it? Why?
In my opinion its better to use 2nd approach. As we know we nowadays heavily uses jquery and want to change view content without having to load whole page.Main reason is partial views are more lightweight than normal views
Sometimes we need to load a partial view , then we can use jQuery to make an AJAX request and render a Partial View . In order to load a partial view with in a div we need to do like as:
<script type="text/jscript">
$('#divforpartialView').load('/Customer/_myAction');
</script>
And moreover idea behind partial view is it is reusable. You can call action which returns partial view like below
<div> #{Html.RenderAction("_Action","Controller");} </div>

Trying to use two layout pages on MVC4 and Razor

When I use #RenderBody on a view (not principal), I receive this message Error: The file "~/Views/Shared/_Sistema.cshtml" cannot be requested directly because it calls the "RenderBody" method.
I do not understand it as I am a novice in MVC.
What do I can do?
Thanks!
If you are using the Renderbody in _Sistema.cshtml file, then make it as a Layout page.
And add another partial page named like MyPartial.cshtml with Layout name as _Sistema.cshtml.
Renderbody is supposed to be in the master page only. i.e., Layout page.
So your _Sistema.cshtml page should only contains the following:
#RenderBody()
#RenderSection("scripts", required: false) #*----Optional---*#
Then your your new partial page MyPartial.cshtml should contain the following:
#{
Layout = "~/_Sistema.cshtml";
}
Then use your partial page in your view as follows:
#Html.Partial("MyPartial")
Hope it helps.
RenderBody is for masters only. This method renders markup of content pages that does not belong to any particular section. If your view calls RenderBody, two cases are possible:
Either this is a mistake and this view should not call it.
Or this view is a master, and you should instead use some other views inheriting layout from this master.
you just need to interact with _ViewStart.cshtml
and use if condition to specify the share mater page for each group of users.
for example user is admin then user _Layout.cshtm other wise use _Layout2.cshtml
use following code :
#{
if(User.Identity.Name.ToLower()=="admin") {
Layout = "~/Views/Shared/_Layout2.cshtml";
}
else {
Layout = "~/Views/Shared/_Layout.cshtml";
}
}
In my experience, I was struggling with this same issue for days. After further investigation, I found that when starting a new Umbraco site, I had the option to select templates. That resolved the RenderBody issue. When creating the layout page without the templates it doesn't see the Master page as the layout, hence not being able to call the RenderBody method. Using the templates automatically sets the Master page as the Layout allowing you to call the RenderBody. I hope this helps.

Can I populate a ContentPlaceHolder in a master page from within a Razor Partial View?

I'm using the typical built in view engine in mvc3 (is there a proper name for it?) for views and master pages and it's including a Razor partial view on the .aspx page. In the masterpage, there is a ContentPlaceHolder with an ID of "ScriptContent".
I want to be able to fill that ContentPlaceHolder from within the Razor partial view but I don't think this is possible. Does anyone know if it is possible and how I would go about doing that?
I already tried rendering it in the partial like so, but that didn't work.
#section ScriptContent {
... content ...
}
It would be very difficult, so much so that I'd recommend finding another way :(. I wish it was easier, but these are the complexities of integrating a new view engine into an existing legacy system.
To give you a head start if you really want to try it: You'd probably need to create a custom base class inheriting from WebViewPage for your Razor content pages, override some of the methods (honestly I'm not too familiar with that aspect so you'd need to debug to follow the pipeline) so that instead of treating the Layout property as the path to a Layout page, you treat it as a Master page. Then you'd need to instantiate the master page and somehow convert the Sections (which were transformed into calls to DefineSection by the Razor parser, and should be stored in a Dictionary somewhere on the base class) in to Content controls and stuff them in the Master Page.
If I haven't boggled your mind by this point, you may just be able to pull this off, but to be honest, I'd avoid it.
P.S. We refer to the older view engine as "ASPX", based on its file extension ;).

MVC3 Layout Page, View, RenderPartial and getting script files into the Header (from the partial view)

So I have a Layout page
<head>
#RenderSection("HeaderLast", required: false)
</head>
A view
#section HeaderLast
{
<script src="#Url.Content("~/Scripts/knockout-1.2.0.js")"
type="text/javascript"></script>
}
<div id="profile-tab">
#{ Html.RenderPartial("_userProfile"); }
</div>
And a Partial view
#section HeaderLast
{
<script type="text/javascript">
alert('test');
</script>
}
<div......
I figured it couldn't be that simple. Is there a proper way to do this out of box or will this always require some kind of mediator and passing stuff around ViewData to manually make the content bubble up to the layout page?
Bounty started: The bounty will be rewarded to the best solution provided for this short coming. Should no answers be provided I will award it to #SLaks for originally answering this question.
You cannot define sections in partial views.
Instead, you can put the Javascript in ViewBag, then emit any Javascript found in ViewBag in the layout page.
#JasCav: If a partial needs its own CSS, it has no good way to get it rendered.
If that's the reason for its use, it could very well be by design.
You don't want to have a separate CSS file x partial/helper. Remember, each separate CSS file means a separate request to get it from the server, thus an additional round-trip that affects time to render your page.
Also you don't want to emit direct CSS to the HTML from the partial/helper. Instead you want it to have appropriate hooks you can use to define all the look in your site's CSS file.
You can use the same hooks you have available for CSS to activate custom JavaScript behaviors for the elements involved When JavaScript is enabled.
Finally it may be the case what you need is not a Partial View, but an extra Layout you use for some pages. With that approach you would have:
A master Layout that gets set automatically on _ViewStart like you probably has now. This defines the sections like in your sample.
A children Layout page. Here you have both the extra html, css, js you need to have for these views. This uses both #RenderBody() and #section SomeSection { } to structure your common extra layout.
Some views that point to the children layout, and others that use the default master layout.
How to get extra data to the children Layout is out of the scope of the question, but you have several options. Like having a common base for your entities; using ViewBag or calling Html.RenderAction to get that shared logic related to shared dynamic elements in the layout.
It looks like there was a similar question on SO - How to render JavaScript into MasterLayout section from partial view?.
Unfortunately, there is no possibility of declaring sections inside Partial Views. That is because RenderPartial ends up rendering totally separate view page. There is a workaround to this, though a bit ugly. But it can look better if using strongly-typed model instead of ViewData.
Basically, you need to keep track of the reference to the view which called RenderPartial and use the DefineSection method on the object passed to push data to that view.
UPDATE: There is also a blog post about dealing with RenderSection you may find useful.
Here is another approach using helper methods and templated delegate
http://blogs.msdn.com/b/marcinon/archive/2010/12/15/razor-nested-layouts-and-redefined-sections.aspx
As a follow up to my question, the JavaScript/CSS combiner/minifier tool Cassette supports this functionality to allow you to compartmentalize your JavaScript and other assets that are required for partials.
I purchased a site license and use this in all of my MVC applications now.

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