I am looking at some razor layout code. I have found the following snippet:
#section Foo
{
#if (#IsSectionDefined("Foo"))
{
#RenderSection("Foo", required: false)
}
}
Wouldn't #section Foo define Foo, meaning that the if (#IsSectionDefined("Foo")) condition would always be true? Also, if that section is defined in another view page, wouldn't this cause a redefinition?
Basically, I don't understand why this condition is wrapped in an #section clause.
I have figured out what this pattern is for: this is used in the situation where there are several layers of layouts. A section definition is scoped to the direct parent layout of a page. Therefore, to define a section that will be rendered in a higher level layout, one must pass it up the hierarchy using this construct.
You define the Sections in a Layout file with RenderSection("Foo");
So here is what I figured out:
The snipped of code doesn't hurt anything by itself.
What it says is this:
If you want to define a #section Foo, you have to define it in some other pages that has the current Layout page. And if you define it, you have to render it by adding #RenderSection("ExtraContent") in Layout page.
In Layout Page:
#section ExtraContent{
#if (#IsSectionDefined("ExtraContent")){
#RenderSection("ExtraContent", required: false)
}
}
#RenderSection("ExtraContent")
In About page:
#section ExtraContent{
<p>Some extra content</p>
}
Related
I'm setting up my ASP.NET Core site with a hierarchy of Razor views, which goes like this:
_Layout
_PanelLayout
Index
So, I have these files:
_ViewStart.cshtml
#{
Layout = "_PanelLayout";
}
_PanelLayout.cshtml
#{
Layout = "_Layout";
}
<div>Panel layout file</div>
#RenderBody()
_Layout.cshtml
<html><body>
<div>Main layout file</div>
#RenderBody()
#RenderSection("scripts", required: false)
</body></html>
Index.cshtml
#section scripts {
<script>
// test script
</script>
}
<div>Content view</div>
When I run a controller action that returns the Index view, I get the error:
InvalidOperationException: The following sections have been defined but have not been rendered by the page at '_PanelLayout.cshtml': 'scripts'.
Why doesn't Razor pick up the fact that the grandparent view of Index is rendering a 'scripts' section? If I remove the section, the layout works fine, so the only problem is this section rendering not carrying through to the grandparent layout. Is there a solution to this problem that still allows me to decide where I want to render the 'scripts' section on the grandparent layout ('_Layout') rather than the parent layout ('_PanelLayout')?
Any sections in parent layouts must be redefined in the child layouts or they will not be available further down the inheritance chain. In other words, in _PanelLayout.cshtml you need to add:
#section scripts
{
#RenderSection("scripts", required: false)
}
This gives a hook to the next level of layout or view referencing this layout (RenderSection) and then stuffs the output of that into the section in _Layout.cshtml.
This might not have an implemented answer but, I was searching for an easy way to render a section block on a controller basis. Obviously _ViewStart is not going to work because it won't know what view to render the section for, but to show you what I mean....
/Shared/_Layout.cshtml
...
#RenderSection("Streetcar", required: false)
...
/_ViewStart.cshtml
...
#{
Layout = "./Shared/_Layout.cshtml";
}
...
/Test/_ViewStart.cshtml
...
#{
// notice layout isn't being set because we still want the global _ViewStart layout
}
#section Streetcar {
Named Desire
}
...
In a perfect world, I could render a section by default for everything single view in the Test folder this way and catch all the views generated by the TestController Since it cannot be done this way, does anyone know of a way of doing this cleanly?
I'm not sure if I understand what you're asking by
Render Section on a Controller by Controller Basis
My answer is predicated on the assumption you just want Nested Master Pages.
So you're right, _ViewStart is a master page switch, not a layout/master page itself. But you can nest master pages:
/Shared/_Layout.cshtml
#RenderBody()
#RenderSection("scripts", required: false)
/_ViewStart.cshtml
#{
Layout = "~/Views/Shared/_Layout.cshtml";
}
/Views/Shared/_TestLayout.cshtml
#{
// References 'global' masterpage
Layout = "~/Views/Shared/_Layout.cshtml";
}
// And override it as necessary
#section scripts {
<script>
console.log("Nested layout ran");
</script>
}
#RenderBody()
/Test/_ViewStart.cshtml
#{
// Set test folder to use test master layout
Layout = "~/Views/Shared/_TestLayout.cshtml";
}
In _Layout.cshtml is it possible to determine what View is going to be rendered in #RenderBody() ?
You can get the View (i.e. Index.cshtml) through ((RazorView)ViewContext.View).ViewPath
Example for your needs:
<script type="text/javascript" src="~/Content/Scripts/#(Path.GetFileNameWithoutExtension(Server.MapPath(((RazorView)ViewContext.View).ViewPath))).js"></script>
If you need your actual View (i.e. _Layout.cshtml), you can use VirtualPath instead.
Old answer
Reading your comments, you want to add a
<script ...>...</script>
depending on the view but outside of #RenderBody()?
Then put
#RenderSection("Scripts", required:false)
and in your view define the section like
#section Scripts {
<script ...>...</script>
}
So you don't need to maintain your _Layout.cshtml since every View defines their own scripts.
Here is an easy explanation: http://weblogs.asp.net/scottgu/asp-net-mvc-3-layouts-and-sections-with-razor
What you can do is check Html.ViewContext.RouteData.Values. That's a dictionary with controller, action, and id (as necessary).
Read this article and it will solve your problem.
Edit
RenderBody
What is RenderBody?
In layout pages, renders the portion of a content page that is not
within a named section. [MSDN]
How RenderBody works (graphical presentation)?
The #RenderBody() renders the view controlled by the controller. so if your controller is like this.
public class HomeController : Controller
{
public ActionResult Index() // Renders File /Views/Home/Index.cshtml
{
return View();
}
}
Then the public ActionResult Index() Index.cshtml will be the view it will render located int the /Views/Home folder.
You can add to the Index.cshtml or _Layout.cshtml view to render other Views or partialViews By adding #Html.Partial("_MyView") as shown below.
#Html.Partial("_LayoutHeaderHeader")
#Html.Partial("_LayoutHeaderNavbar")
Sometimes it is easy to setup a few layout pages to call from different Views.
If you want to call scripts to you View you should always create a _PartialView and place your scripts in the partial view and call that View at the bottom of your View like this #Html.Partial("_MyView") and the scripts will set properly.
Here is a good tutorial. http://www.codeproject.com/Articles/698246/ASP-NET-MVC-Special-Views-Partial-View-and-Layout
If you derive all your models from a base model then you could add a property to you base model that returns the controller name, which you can get using
this.RouteData.Values["controller"].ToString();
It would be even better if you had a BaseController class because you could put this in the constructor and never have to touch it again.
Since you would be returning a descendant of the base Model to your index page which has the controller name, now you could use some scheme base on #Model.ControllerName. If your controller services multiple views the property could be updated to indicate a certain view name.
I don't think you can get the name of a Partial inside the index unless you use jquery and by that point the page resources have already been loaded.
Edit: One other trick would be to create your own version of #Html.Partial() HtmlHelper class. So you have #Html.MyPartial("ViewName") and inside that method call the internal function that generates Html.Partial and then inject your dependencies.
EDIT: I just read your comments about the issue and think that the better way is using the code snipplet provided by #Matt in another answer.
You can use the #section razor statement inside your view to inform wich script should be loaded.
Layout template placeholder
#RenderSection("scripts", required: false)
View Code
#section scripts {
<script src="~/Scripts/custom-imgedit.js"></script>
}
The example above inform that the custom-imgedit.js will be loaded in the render section placeholder. Note: You can even use bundles like #Scripts.Render("~/bundles/myCustomScripts")
If I have a page with:
<body>
#section SomeStuff {
<span>This is a section I just addered</span>
}
</body>
Is it possible for the layout to not render this section, or is that contrary to how this should work conceptually. Seems like it would be useful to be able to not render certain sections on a page (unless I'm thinking about this incorrectly).
Edit:
Including the error message may be helpful, when I put a section into the main page, the layout page fails with: The following sections have been defined but have not been rendered for the layout page "/Views/Layouts/_Layout1.cshtml": "SomeStuff". As if it's forcing me to render every section on the page or something.
In otherwords, in Layout.cshtml, I don't call #RenderSection, but in Index.html I have a section called SomeStuff defined. Is that legal? Seems like it's forcing me to render all sections in the page, but that seems like sections should be optional, no?
you can specify if a section is required.
#RenderSection("SomeStuff", required: false)
if you don't render it out in a view, it shouldn't error then, noted here
http://weblogs.asp.net/scottgu/archive/2010/12/30/asp-net-mvc-3-layouts-and-sections-with-razor.aspx
You can set a section to be optional by setting the required parameter to false. If you'd like to include some optional wrapper HTML around your section then you can also use the IsSectionDefined method.
#if(IsSectionDefined("SideBar"))
{
<div class="sidebar">
#RenderSection("SideBar", required: false)
</div>
}
For a certain layout not to render certain section you need to have something like this is your layout.cshtml
#RenderSection("Somestuff", required:false)
You could do:
#if (condition) {
#RenderSection("SomeStuff")
}
Or just use a conditional statement directly rather than #RenderSection:
#if (yourCondition) {
<span>This is a section I just addered</span>
}
I encountered a similar issue when I was trying to dynamically inject code into an inline script, I solved it via:
#if (someCondition)
{
#Html.Raw(#"
Your stuff here
");
}
Let's say I have the following structure in my ASP.NET MVC 3 application.
Items
Index.cshtml
Categories
Shared
_Index.cshtml
_Site.cshtml
Index.cshtml
Both Index.cshtml files use _Index.cshtml as the layout page and _Index is nested within the _Site layout.
Items/Index implements the optional sections defined in _Index. Shared/Index is empty.
The Items/Index view works fine. Since Categories doesn't have an Index, it uses the one in the Shared folder. This does not work.
It throws the error
The "RenderBody" method has not been called for layout page "~/Views/Shared/_Index.cshtml".
If _Site calls RenderBody, and _Index inherits from _Site, doesn't the content in _Index satisfy the required RenderBody call and Shared/Index.cshtml can be blank?
The reason I ask is because I have an ASP.NET MVC 1 application that implemented this structure using Master pages and it worked fine, but converting it to MVC 3 with Razor is causing this issue.
Here is the basic outline of what I'm describing:
_Site.cshtml
<!DOCTYPE html>
// head
<body>
#RenderBody()
</body>
_Index.cshtml
#{
Layout = "~/Views/Shared/_Site.cshtml";
}
<div id="sub-menu">
// Markup
</div>
// More markup
#RenderSection("SectionOne", required: false)
#RenderSection("SectionTwo", required: false)
Items/Index.cshtml (Working)
#{
Layout = "~/Views/Shared/_Index.cshtml";
}
#section SectionOne {
// Markup
}
Shared/Index.cshtml (RenderBody error)
#{
Layout = "~/Views/Shared/_Index.cshtml";
}
// Rest of this file is empty
I'm not sure i follow you completely, but ALL layout pages have to have a RenderBody(), even if they're nested. RenderBody() renders the content for the "child". When you have nested layout pages the nested layout is the child of the parent, and it's output must be rendered in the RenderBody. Likewise, the child of the child has to render it's body into the middle page.
To put it another way, anything that's not in a #section is considered the "body". So, _Index.cshtml needs to render it's body (Index.cshtml) and _Site.html has to render it's body (_Index.cshtml). It goes up the chain.
EDIT:
It appears that a layout has to render at least one section, be it with a RenderBody() or a RenderSection(). While it may be true that the sections are optional, rendering at least one section is not. Either add an empty section to your Index.cshtml or add a RenderBody() to your _Index.cshtml.