Asp.Net Core Layout And Sections Complete Guide

 Last Update:2025-06-23T00:00:00     .NET School AI Teacher - SELECT ANY TEXT TO EXPLANATION.    7 mins read      Difficulty-Level: beginner

Understanding the Core Concepts of ASP.NET Core Layout and Sections

Layouts in ASP.NET Core

Definition: Layouts in ASP.NET Core allow you to define a common template or structure for your views, which can reuse components like headers, menus, footers across different pages without duplicating code. Essentially, a layout is a view that provides a template for other views.

Important Info:

  • Shared Directory: Layouts are typically stored in the Views/Shared directory.
  • _ViewStart.cshtml: This file sets up a default layout for all views in the application unless specified otherwise.
  • Default Layout: The _Layout.cshtml file inside the Views/Shared directory serves as the default layout unless you configure otherwise.
  • @RenderBody(): This is a rendering helper used within the layout to display the content of the current view.
  • @RenderSection(): You can define optional or required sections within a layout, allowing you to insert specific content into designated areas.

Creating a Layout

  1. Create a Layout File:

    • Navigate to the Views/Shared folder of your project.
    • Add a new Razor view (e.g., _CustomLayout.cshtml).
    • Use HTML to set up your desired structure and include placeholders for dynamic content.

  2. Example of a Layout:

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>@ViewData["Title"] - My ASP.NET Core App</title>
    <link rel="stylesheet" href="~/lib/bootstrap/dist/css/bootstrap.min.css" />
    <link rel="stylesheet" href="~/css/site.css" />
</head>
<body>
    <header>
        <nav class="navbar navbar-expand-sm navbar-toggleable-sm navbar-light bg-white border-bottom box-shadow mb-3">
            <div class="container">
                <a class="navbar-brand" asp-area="" asp-controller="Home" asp-action="Index">My ASP.NET Core App</a>
                <button class="navbar-toggler" type="button" data-toggle="collapse" data-target=".navbar-collapse" aria-controls="navbarSupportedContent"
                        aria-expanded="false" aria-label="Toggle navigation">
                    <span class="navbar-toggler-icon"></span>
                </button>
                <div class="navbar-collapse collapse d-sm-inline-flex justify-content-between">
                    <ul class="navbar-nav flex-grow-1">
                        <li class="nav-item">
                            <a class="nav-link text-dark" asp-area="" asp-controller="Home" asp-action="Index">Home</a>
                        </li>
                        <li class="nav-item">
                            <a class="nav-link text-dark" asp-area="" asp-controller="Home" asp-action="Privacy">Privacy</a>
                        </li>
                    </ul>
                </div>
            </div>
        </nav>
    </header>
    <div class="container">
        <main role="main" class="pb-3">
            @RenderBody() <!-- Dynamic Content Here -->
        </main>
    </div>
    <footer class="border-top footer text-muted">
        <div class="container">
            &copy; @DateTime.Now.Year - My ASP.NET Core App - <a asp-area="" asp-controller="Home" asp-action="Privacy">Privacy</a>
        </div>
    </footer>
</body>
</html>

Sections in ASP.NET Core

Definition: Sections allow you to inject specific content from child views into predefined placeholder sections within a layout. This is useful for content such as scripts, stylesheets, or other elements that need to be placed in specific areas of the layout.

Important Info:

  • Optional Sections: By default, sections are optional in a layout. Child views can choose not to override them.
  • Required Sections: If you want a section to be required, use the overloaded method @RenderSection() with the second parameter set to true.
  • Multiple Sections: A layout can have multiple sections, allowing for granular control over content placement.

Using Sections in Views

  1. Define a Section in the Layout:

    • Use the @RenderSection() helper method.
    • Optionally specify whether the section is required.
    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>@ViewData["Title"] - My ASP.NET Core App</title>
    <link rel="stylesheet" href="~/lib/bootstrap/dist/css/bootstrap.min.css" />
    <link rel="stylesheet" href="~/css/site.css" />
    @RenderSection("HeadScripts", required: false) <!-- Optional Section -->
</head>
<body>
    ...
    @RenderSection("Scripts", required: true) <!-- Required Section -->
</body>
</html>

  2. Override a Section in a Child View:

    • Use the @section directive in child views to inject content.

    Example of a Child View Using Sections:

    @model YourNamespace.Models.YourModel
@layout "_CustomLayout" // Specify a custom layout if needed

@{
    ViewData["Title"] = "Home Page";
}

<script>
    @section HeadScripts
    {
        <script src="~/lib/some-head-script.js"></script>
    }

    <h1>Welcome to My ASP.NET Core Application</h1>
    <p>This is a sample home page.</p>

    @section Scripts
    {
        <script src="~/lib/some-footer-script.js"></script>
    }
}

Benefits of Using Layouts and Sections

  • Code Reusability: Promotes DRY (Don't Repeat Yourself) principle by avoiding duplication of header, footer, and menu across multiple views.
  • Consistent Appearance: Ensures that all views share the same consistent look and feel.
  • Modularity: Simplifies the management of your project’s UI components by breaking down large files into smaller, manageable ones.
  • Maintenance Efficiency: Easier to maintain and update the site’s layout since changes made in one place reflect across all views using that layout.

Advanced Usage

  • Nested Layouts: Layouts themselves can inherit from another layout, creating multi-level template structures.
  • Overriding Layouts Per View: Each view can individually specify which layout it should use by setting the Layout property.
  • Partial Views: These can be included in layouts or views to further modularize your UI components.

By understanding and leveraging layouts and sections in ASP.NET Core, you can improve the scalability and maintainability of your web application, making it easier to add more pages with consistent styling and functionality.

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Step-by-Step Guide: How to Implement ASP.NET Core Layout and Sections

Step 1: Create a New ASP.NET Core Project

  1. Open Visual Studio.
  2. Go to File > New > Project.
  3. Select ASP.NET Core Web App (Model-View-Controller) and click Next.
  4. Name your project (e.g., AspNetCoreLayoutExample) and click Create.
  5. Choose the target framework (e.g., .NET 6.0 or later) and click Create.

Step 2: Set Up the Layout

  1. Go to the Views folder in the Solution Explorer.
  2. Inside the Views folder, create a new folder named Shared.
  3. Right-click on the Shared folder, go to Add > New Item.
  4. Select Razor View and name it _Layout.cshtml.

Replace the contents of _Layout.cshtml with the following code:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>@ViewData["Title"] - ASP.NET Core Layout Example</title>
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css" />
</head>
<body>
    <header>
        <nav class="navbar navbar-expand-sm navbar-toggleable-sm navbar-light bg-white border-bottom box-shadow mb-3">
            <div class="container">
                <a class="navbar-brand" asp-area="" asp-controller="Home" asp-action="Index">AspNetCoreLayoutExample</a>
                <button class="navbar-toggler" type="button" data-toggle="collapse" data-target=".navbar-collapse" aria-controls="navbarSupportedContent"
                        aria-expanded="false" aria-label="Toggle navigation">
                    <span class="navbar-toggler-icon"></span>
                </button>
                <div class="navbar-collapse collapse d-sm-inline-flex flex-sm-row-reverse">
                    <ul class="navbar-nav flex-grow-1">
                        <li class="nav-item">
                            <a class="nav-link text-dark" asp-area="" asp-controller="Home" asp-action="Index">Home</a>
                        </li>
                        <li class="nav-item">
                            <a class="nav-link text-dark" asp-area="" asp-controller="Home" asp-action="Privacy">Privacy</a>
                        </li>
                    </ul>
                </div>
            </div>
        </nav>
    </header>
    <div class="container">
        <main role="main" class="pb-3">
            @RenderBody()
        </main>
    </div>

    <footer class="border-top footer text-muted">
        <div class="container">
            &copy; 2023 - ASP.NET Core Layout Example - <a asp-area="" asp-controller="Home" asp-action="Privacy">Privacy</a>
        </div>
    </footer>

    <script src="https://code.jquery.com/jquery-3.5.1.slim.min.js"></script>
    <script src="https://cdn.jsdelivr.net/npm/@popperjs/core@2.5.2/dist/umd/popper.min.js"></script>
    <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/js/bootstrap.min.js"></script>
    <script src="~/js/site.js" asp-append-version="true"></script>

    @RenderSection("Scripts", required: false)
</body>
</html>

Step 3: Use the Layout in a View

  1. Open the Views folder and go to Views/Home.
  2. Open the Index.cshtml file.

Replace the contents of Index.cshtml with the following code:

@{
    ViewData["Title"] = "Home Page";
    Layout = "_Layout";
}

@section Scripts {
    <script>
        document.addEventListener('DOMContentLoaded', function () {
            alert('Index page loaded!');
        });
    </script>
}

<div class="text-center">
    <h1 class="display-4">Welcome</h1>
    <p>Learn about <a href="https://docs.microsoft.com/aspnet/core">building Web apps with ASP.NET Core</a>.</p>
</div>

Step 4: Define a Custom Section in the Layout

  1. Open the _Layout.cshtml file in the Views/Shared folder.
  2. Add a custom section to the layout file, for example, a Head section.

Modify the _Layout.cshtml file as follows:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>@ViewData["Title"] - ASP.NET Core Layout Example</title>
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css" />
    @RenderSection("Head", required: false)
</head>
<body>
    <header>
        <nav class="navbar navbar-expand-sm navbar-toggleable-sm navbar-light bg-white border-bottom box-shadow mb-3">
            <div class="container">
                <a class="navbar-brand" asp-area="" asp-controller="Home" asp-action="Index">AspNetCoreLayoutExample</a>
                <button class="navbar-toggler" type="button" data-toggle="collapse" data-target=".navbar-collapse" aria-controls="navbarSupportedContent"
                        aria-expanded="false" aria-label="Toggle navigation">
                    <span class="navbar-toggler-icon"></span>
                </button>
                <div class="navbar-collapse collapse d-sm-inline-flex flex-sm-row-reverse">
                    <ul class="navbar-nav flex-grow-1">
                        <li class="nav-item">
                            <a class="nav-link text-dark" asp-area="" asp-controller="Home" asp-action="Index">Home</a>
                        </li>
                        <li class="nav-item">
                            <a class="nav-link text-dark" asp-area="" asp-controller="Home" asp-action="Privacy">Privacy</a>
                        </li>
                    </ul>
                </div>
            </div>
        </nav>
    </header>
    <div class="container">
        <main role="main" class="pb-3">
            @RenderBody()
        </main>
    </div>

    <footer class="border-top footer text-muted">
        <div class="container">
            &copy; 2023 - ASP.NET Core Layout Example - <a asp-area="" asp-controller="Home" asp-action="Privacy">Privacy</a>
        </div>
    </footer>

    <script src="https://code.jquery.com/jquery-3.5.1.slim.min.js"></script>
    <script src="https://cdn.jsdelivr.net/npm/@popperjs/core@2.5.2/dist/umd/popper.min.js"></script>
    <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/js/bootstrap.min.js"></script>
    <script src="~/js/site.js" asp-append-version="true"></script>

    @RenderSection("Scripts", required: false)
</body>
</html>

Step 5: Use the Custom Section in a View

  1. Open the Views folder and go to Views/Home.
  2. Open the Index.cshtml file.
  3. Add the custom section to the Index.cshtml file.

Modify the Index.cshtml file as follows:

Top 10 Interview Questions & Answers on ASP.NET Core Layout and Sections

1. What is the purpose of a Layout in ASP.NET Core?

Answer: A Layout in ASP.NET Core serves as a template for your views. It defines the HTML structure used across multiple views (pages) in your application, allowing you to maintain consistency and reduce redundancy. For example, a typical Layout might include headers, footers, and navigation bars that are shared among different pages.

2. How do you create a Layout in ASP.NET Core?

Answer: To create a Layout, you need to define a .cshtml file in the Views/Shared folder that contains the shared markup. Start by creating this layout using the Razor syntax, typically named _Layout.cshtml. Here’s a simple example:

<!DOCTYPE html>
<html>
<head>
    <title>@ViewData["Title"] - MyApp</title>
</head>
<body>
    <header>Application Header here</header>
    <main>
        @RenderBody()
    </main>
    <footer>Application Footer here</footer>
</body>
</html>

3. What does the @RenderBody() method do in a Layout?

Answer: The @RenderBody() method within a Layout file is a placeholder that outputs the content of individual views when they are rendered within the Layout. Essentially, it tells the framework where to insert the page-specific content into the overall HTML document structure.

4. How do you apply a Layout to a specific view in ASP.NET Core?

Answer: You can apply a Layout to a specific view by setting the Layout property at the beginning of the view file.

@{
    Layout = "_Layout";
}

You can also set the default Layout for all views in the application or in specific folders by defining a _ViewStart.cshtml file with the following content:

@{
    Layout = "_Layout";
}

5. What are Sections in ASP.NET Core and how do you use them?

Answer: Sections in ASP.NET Core allow you to render specific parts of page content into designated places within the Layout. You define sections in your views and then reference them in your Layout using @RenderSection.

To define a Section in a view:

@section Scripts {
    <script src="~/js/viewSpecificScript.js"></script>
}

In the Layout, you declare the Section:

@RenderSection("Scripts", required: false)

The required: false parameter indicates that the section is optional; if the view doesn't provide any content for the section, the page won't throw an error.

6. Can you have multiple Sections in a single Layout?

Answer: Yes, a single Layout can contain multiple Sections. Each Section is declared and rendered separately. This allows for flexible placement of content across different parts of your web pages.

For instance:

<header>
    @RenderSection("Header", required: false)
</header>
<main>
    @RenderBody()
</main>
<footer>
    @RenderSection("Footer", required: false)
</footer>

7. What happens if a Section marked as required is not provided in a view?

Answer: If a Section in the Layout is marked as required (by setting required: true or omitting the required parameter), and the view does not provide that Section's content, the framework will throw an exception. This ensures that you don’t accidentally forget to include critical content on certain pages.

Example:

@RenderSection("CriticalSection")

8. How do you nest Layouts? (e.g., child layouts)

Answer: Nesting Layouts is useful for creating more granular, reusable structures. To nest a Layout, you set the Layout property in a child Layout file to another Layout file.

For instance, say you have a main layout _MainLayout.cshtml and another layout _ChildLayout.cshtml:

_MainLayout.cshtml:

<!DOCTYPE html>
<html>
<head>
    <title>Main Layout Title</title>
</head>
<body>
    <header>Main Header</header>
    <main>
        @RenderBody()
    </main>
    <footer>Main Footer</footer>
</body>
</html>

_ChildLayout.cshtml:

@{
    Layout = "_MainLayout";
}
<article>
    @RenderBody()
</article>

Then, views using _ChildLayout will automatically use _MainLayout as well:

_View.cshtml:

@{
    Layout = "_ChildLayout";
}
<p>This content is in the Child Layout.</p>

9. How can you override the Layout in a specific view?

Answer: Sometimes you may want a specific view to use a different Layout than what is specified in _ViewStart.cshtml. To do so, explicitly set the Layout property in that particular view.

@{
    Layout = "_DifferentLayout"; // or Layout = null; to use no layout
}

10. Why should I use Partial Views instead of Sections sometimes?

Answer: Partial Views and Sections both help organize and reuse code, but they serve slightly different purposes. Partial Views are ideal for rendering smaller, independent pieces of UI that might be reused across multiple pages, such as forms, menus, or widgets. On the other hand, Sections are better suited for defining placeholders in a Layout where specific content from a view needs to be inserted.

Partial Views are included directly in a View using @await Html.PartialAsync("_PartialViewName") or the shorthand @Html.Partial("_PartialViewName").

Conclusion:

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