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Sections in Layout View in ASP.NET Core MVC
In this article, I am going to discuss the Sections in Layout View in ASP.NET Core MVC Application. Please read our previous article, where we discussed the Layout View in ASP.NET Core MVC Application. We will also work with the same example we created in our previous article. As part of this article, we are going to discuss the following pointers.
- What are Sections?
- What is the need for Sections in Layout View in ASP.NET Core MVC Application?
- Understanding the RenderSection Method.
- How to use the RenderSection Method in ASP.NET Core MVC?
- How to Provide Section Content in a View?
- Understanding How to make the layout section optional in ASP.NET Core MVC?
Sections in Layout View in ASP.NET Core MVC Application:
Sections in ASP.NET Core MVC layout views allow you to define and inject content from individual views into specific predefined areas of the layout. This concept is powerful for creating a consistent layout while allowing view-specific content flexibility. Sections help you organize your code and maintain common structure and styling across various pages.
Sections in ASP.NET Core MVC layout views provide a way to define content blocks that child views can fill. They allow you to define placeholders in the layout view for specific content that varies from page to page. This mechanism is helpful for creating flexible and customizable layouts where different views can inject their own content into specific sections of the layout.
In ASP.NET Core MVC, the layout view contains one or more sections in it. The Sections in a layout view are used to organize where certain page elements should be placed. The sections in a layout view can be optional or mandatory. If this is unclear now, don’t worry; we will understand this with examples and see when it is mandatory and optional.
Understanding the Need for Sections in a Layout View with an Example:
In order to understand Need for Sections in a Layout View, let us first create a custom javascript file. First, create a folder at the root level of the application with the name wwwroot if not already there. As we are creating the project using Model-View-Controller, so the wwwroot folder should be there.
In general, all the static files of our ASP.NET Core MVC Application need to be placed within this wwwroot folder. Once you have created the “wwwroot” folder, within wwwroot folder, create a subfolder within this with the name “js” if not already there, and then add a javascript file with the name “CustomJavascript.js” within the js folder.
To do so, right-click on the js folder and then select Add => New Item from the context menu, which will open the New Item window. Here, search javascript, select Javascript File, give the file name CustomJavascript.js, and finally click on the Add button, as shown in the image below.
Once you add the CustomJavascript.js file, your wwwroot folder should look as shown in the below image.
Situation1:
If we have a custom javascript file (i.e., CustomJavascript.js) and all the views of our application require that file, then we need to place that file in the Layout View of our application. Let us add that CustomJavascript.js file within our _Layout.cshtml file. So, modify the _Layout.cshtml file as follows.
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width" />
<title>@ViewBag.Title</title>
</head>
<body>
<table border="1" style="width:800px; font-family:Arial">
<tr>
<td colspan="2" style="text-align:center">
<h3>Website Header</h3>
</td>
</tr>
<tr>
<td style="width:200px">
<h3>Left Navigation Menus</h3>
</td>
<td style="width:600px">
@RenderBody()
</td>
</tr>
<tr>
<td colspan="2" style="text-align:center; font-size:x-small">
<h3>Website Footer</h3>
</td>
</tr>
</table>
<script src="~/js/CustomJavascript.js"></script>
</body>
</html>
Note: Putting all the script files before the closing body tag is always a good programming practice.
Situation2:
If you have a custom javascript file (i.e., CustomJavascript.js) and you want that file in some specific views. Let’s assume you want that file in the Index view but not in the Details view of the Home Controller. In such scenarios, you can make use of the Section in ASP.NET Core MVC Application.
Understanding the RenderSection Method:
To use Section in ASP.NET Core MVC, we are provided with the RenderSection and RenderSectionAsync methods. Let us have a look at the signature of the RenderSection and RenderSectionAsync methods which are shown below.
As you can see, two overloaded versions of the RenderSection Method exist. The same is the case for the RenderSectionAsync method. The first version of the Render section method takes a single parameter (i.e., name) that specifies the name of the section. The second overloaded version takes two parameters. The first parameter (name) specifies the name of the section, while the second parameter (required) specifies whether the section is required or optional.
How to use the RenderSection Method in ASP.NET Core MVC?
From your layout view, you need to call the RenderSection() method at the location where you want the section content to be rendered. For example, we want the script file to be included just before the closing </body> tag. So, here, we are calling the @RenderSection() method just before the closing </body> tag, as shown below.
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width" />
<title>@ViewBag.Title</title>
</head>
<body>
<table border="1" style="width:800px; font-family:Arial">
<tr>
<td colspan="2" style="text-align:center">
<h3>Website Header</h3>
</td>
</tr>
<tr>
<td style="width:200px">
<h3>Left Navigation Menus</h3>
</td>
<td style="width:600px">
@RenderBody()
</td>
</tr>
<tr>
<td colspan="2" style="text-align:center; font-size:x-small">
<h3>Website Footer</h3>
</td>
</tr>
</table>
@RenderSection("Scripts")
</body>
</html>
In the above code, we use the first overloaded version of the RenderSection method, which only takes the name parameter. In this case, the second parameter value will be true by default. That means mandatory.
How to Provide Section Content in a Child View?
In our layout view, we have created a section. Now let us understand how to provide section content from the Child Views. Each and every view which wants to provide section content must include a section within the view. And to do this, we need to use the @section directive to include the section and provide the content.
In our example, we want to provide the section content from the Index view. So, we need to modify the Index view as shown below. Here, you can see we are using @section Scripts {<script src=”~/js/CustomJavascript.js”></script>} as we are trying to include a javascript file. Here, we need to provide the section name as Scripts, and this is because, in the _Layout view, we have specified the section name as Scripts, i.e., @RenderSection(“Scripts”)
@{
ViewBag.Title = "Home Page";
Layout = "~/Views/Shared/_Layout.cshtml";
}
<h1>Home Page</h1>
@section Scripts {
<script src="~/js/CustomJavascript.js"></script>
}
Now run the application and navigate to the Home/Index URL, and you will see the out as expected, as shown in the below image.
But, when you navigate to the Home/Details URL, you will get the following error page.
The reason for getting the above exception is the section is mandatory, and we have not specified the section content in the Details view. To verify this, go to the definition of the RenderSection(“Scripts”) method, which takes the string file name as a parameter, and you will see the following. As you can see, this method takes only the name parameter, and internally it sets the required parameter value to true, making it mandatory to include the section in the child view. And in the Details view, we have not included any section.
How to make the Layout Section Optional in ASP.NET Core MVC?
We can make a layout section optional in ASP.NET Core MVC in two ways. They are as follows:
Way1: Use the RenderSection method, which takes two parameters. Set the second parameter (i.e., the required) to false.
@RenderSection(“Scripts”, required: false)
So, modify the _Layout.cshtml file as shown below to make the section optional.
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width" />
<title>@ViewBag.Title</title>
</head>
<body>
<table border="1" style="width:800px; font-family:Arial">
<tr>
<td colspan="2" style="text-align:center">
<h3>Website Header</h3>
</td>
</tr>
<tr>
<td style="width:200px">
<h3>Left Navigation Menus</h3>
</td>
<td style="width:600px">
@RenderBody()
</td>
</tr>
<tr>
<td colspan="2" style="text-align:center; font-size:x-small">
<h3>Website Footer</h3>
</td>
</tr>
</table>
@RenderSection("Scripts", false)
</body>
</html>
With the above changes in place, run the application and navigate to both URLs, and you should get the output as expected.
Way2: Using the IsSectionDefined() method.
This method returns a value indicating whether the specified section is defined on the child view or not. If the section is defined in the child view, then IsSectionDefined() method returns true, and in that case, the RenderSection method going to load the content from the child view. If the method returns false, then the RenderSection method is not going to be executed and be ignored. So, modify the _Layout.cshtml file as shown below.
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width" />
<title>@ViewBag.Title</title>
</head>
<body>
<table border="1" style="width:800px; font-family:Arial">
<tr>
<td colspan="2" style="text-align:center">
<h3>Website Header</h3>
</td>
</tr>
<tr>
<td style="width:200px">
<h3>Left Navigation Menus</h3>
</td>
<td style="width:600px">
@RenderBody()
</td>
</tr>
<tr>
<td colspan="2" style="text-align:center; font-size:x-small">
<h3>Website Footer</h3>
</td>
</tr>
</table>
@if (IsSectionDefined("Scripts"))
{
@RenderSection("Scripts")
}
</body>
</html>
With the above changes in place, run the application and navigate to both URLs, and you should get the output as expected.
Use Cases of Sections in Layout View in ASP.NET Core MVC
Sections in ASP.NET Core MVC layout views are powerful tools for creating flexible and customizable layouts. They allow you to inject dynamic content into specific sections of your layout from individual views. Here are some common use cases for using sections:
- Page-Specific Title and Meta Tags: You can use sections to inject page-specific titles, meta tags, and other SEO-related content into the <head> section of your layout. This is especially useful for improving search engine optimization.
- Custom Styles and Scripts: Sections are ideal for injecting page-specific CSS stylesheets and JavaScript files. This allows you to include only the necessary resources for each view, enhancing performance.
- Page-Level Scripts: If a particular view requires specific JavaScript code, you can use a section to inject the scripts directly into the layout’s <body> section.
- Additional Head Content: Apart from title and meta tags, you might have other <head> content that is unique to certain views. Sections enable you to add that content dynamically.
- Custom Sidebar Widgets: If you have a sidebar that contains dynamic widgets, you can use a section to insert those widgets into the layout.
- Custom Headers and Footers: You might want to customize headers and footers on a per-page basis. Sections allow you to inject page-specific content while keeping the overall structure consistent.
- Conditional Elements: If you need to display different elements on different pages (e.g., banners, call-to-action buttons), you can use sections to inject those elements conditionally.
- Alternate Layouts: Sections can facilitate alternate layouts for specific pages or sections of your application. You can have different sections or layouts for different areas of your site.
- Mobile/Desktop Versions: For responsive designs, sections can help you provide different content or layouts for mobile and desktop versions of your site.
- Content Blocks: In cases where you want to provide flexible content blocks that can be inserted in different places of the layout, sections can be useful.
- Widget Injection: If you’re using a widget-based architecture, sections allow you to inject widget-specific content into predefined areas of the layout.
In summary, sections in layout views provide a way to inject dynamic content into specific parts of your application’s UI while maintaining a consistent structure. They enable you to tailor your layout to the needs of each view and enhance the customization and flexibility of your application’s user interface.
Advantages and Disadvantages of Sections in Layout View in ASP.NET Core MVC
Advantages of Sections:
- Customization: Sections allow you to customize specific parts of your layout on a per-page basis. This is especially helpful when different pages have unique content or requirements.
- Consistency: While sections enable customization, they also help maintain consistency by providing a structure that remains consistent across different views.
- Separation of Concerns: Sections promote the separation of concerns by allowing you to define content in individual views while keeping the layout structure in a separate layout file.
- Code Reusability: You can reuse sections across multiple views, avoiding redundancy and making it easier to update common elements.
- Extensibility: Layout views with sections can be extended by child views, allowing you to modify specific sections while inheriting the structure and content from the layout.
- Conditional Content: Sections facilitate injecting conditional content based on view requirements, enhancing your application’s UI flexibility.
- Focused Content Management: By isolating content within sections, you can focus on managing specific content blocks without affecting the entire layout.
Disadvantages of Sections:
- Complexity: Sections can lead to increased complexity, especially when dealing with multiple sections in different views. This complexity might make the code harder to understand and maintain.
- Overhead: For small applications or views with minimal variation, using sections might introduce unnecessary overhead and code.
- Potential Overuse: While sections are valuable for customizing content, overusing them could lead to bloated layouts and code.
- Learning Curve: Developers who are new to ASP.NET Core MVC might require some time to understand the concept of sections and how to use them effectively.
- Maintenance: As your application grows, maintaining numerous sections in different views could become challenging if not organized properly.
- Abstraction and Indirection: Sections introduce an abstraction layer between the view and the layout, which might add a level of indirection and potentially obscure the layout structure.
In summary, sections provide a powerful way to create dynamic and customizable layouts, enhancing the flexibility and maintainability of your application’s user interface. However, it’s important to use them judiciously and maintain a balance between customization and complexity. Consider the needs of your application, the frequency of content variation, and the skill level of your development team when deciding how extensively to use sections.
In the next article, I am going to discuss the _ViewStart.cshtml in ASP.NET Core MVC Application. Here, in this article, I try to explain the Sections in the Layout Page in ASP.NET Core MVC Application.
i need book of asp.net mvc core ..same topics as cover on website.
Not for publish :
“CustomJavascript.js” within the js folder as shown in the below image.
instead of
“CustomJavascript.cs” within the js folder as shown in the below image.
As you can see there are two overloaded versions of the RenderSection Method.
instead of
As you can there are two overloaded versions of the RenderSection Method.
Hi,
Thanks for identifying the typographical error. We have corrected it.
Thanks it was useful for me