Markup Syntax

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QnA is a markup language for people with little or no programming experience. It was designed with attorneys in mind and transforms blocks of text into interactive question and answer sessions (QnAs). Razor is a markup syntax for embedding server-based code into webpages. The Razor syntax consists of Razor markup, C#, and HTML. Files containing Razor generally have a.cshtml file extension. Razor is also found in Razor components files (.razor).

The Help page, Markup Syntax, lists all the different syntax options described in this section. Linking to a Page You can include links in page sections to other pages in a Websheet by using the following syntax. The syntax of SGML is closer to the COCOA format. As a document markup language, SGML was originally designed to enable the sharing of machine-readable large-project documents in government, law, and industry. Many such documents must remain readable for several decades—a long time in the information technology field. Markup syntax should be easily parsed with simple regular expressions to support a wide variety of implementations. Critic Markup shall be compatible with existing markup syntax for Markdown, MultiMarkdown and HTML except where it conflicts with rules one or two.

Markup Syntax

By Rick Anderson, Taylor Mullen, and Dan Vicarel

Razor is a markup syntax for embedding server-based code into webpages. The Razor syntax consists of Razor markup, C#, and HTML. Files containing Razor generally have a .cshtml file extension. Razor is also found in Razor components files (.razor).

Rendering HTML

The default Razor language is HTML. Rendering HTML from Razor markup is no different than rendering HTML from an HTML file. HTML markup in .cshtml Razor files is rendered by the server unchanged.

Razor syntax

Razor supports C# and uses the @ symbol to transition from HTML to C#. Razor evaluates C# expressions and renders them in the HTML output.

When an @ symbol is followed by a Razor reserved keyword, it transitions into Razor-specific markup. Otherwise, it transitions into plain C#.

To escape an @ symbol in Razor markup, use a second @ symbol:

The code is rendered in HTML with a single @ symbol:

HTML attributes and content containing email addresses don't treat the @ symbol as a transition character. The email addresses in the following example are untouched by Razor parsing:

Implicit Razor expressions

Implicit Razor expressions start with @ followed by C# code:

With the exception of the C# await keyword, implicit expressions must not contain spaces. If the C# statement has a clear ending, spaces can be intermingled:

Implicit expressions cannot contain C# generics, as the characters inside the brackets (<>) are interpreted as an HTML tag. The following code is not valid:

The preceding code generates a compiler error similar to one of the following:

  • The 'int' element wasn't closed. All elements must be either self-closing or have a matching end tag.
  • Cannot convert method group 'GenericMethod' to non-delegate type 'object'. Did you intend to invoke the method?`

Generic method calls must be wrapped in an explicit Razor expression or a Razor code block.

Explicit Razor expressions

Explicit Razor expressions consist of an @ symbol with balanced parenthesis. To render last week's time, the following Razor markup is used:

Any content within the @() parenthesis is evaluated and rendered to the output.

Implicit expressions, described in the previous section, generally can't contain spaces. In the following code, one week isn't subtracted from the current time:

The code renders the following HTML:

Explicit expressions can be used to concatenate text with an expression result:

Without the explicit expression, <p>[email protected]</p> is treated as an email address, and <p>[email protected]</p> is rendered. When written as an explicit expression, <p>Age33</p> is rendered.

Explicit expressions can be used to render output from generic methods in .cshtml files. The following markup shows how to correct the error shown earlier caused by the brackets of a C# generic. The code is written as an explicit expression:

Expression encoding

C# expressions that evaluate to a string are HTML encoded. C# expressions that evaluate to IHtmlContent are rendered directly through IHtmlContent.WriteTo. C# expressions that don't evaluate to IHtmlContent are converted to a string by ToString and encoded before they're rendered.

The preceding code renders the following HTML:

The HTML is shown in the browser as plain text:

<span>Hello World</span>

HtmlHelper.Raw output isn't encoded but rendered as HTML markup.

Warning

Using HtmlHelper.Raw on unsanitized user input is a security risk. User input might contain malicious JavaScript or other exploits. Sanitizing user input is difficult. Avoid using HtmlHelper.Raw with user input.

The code renders the following HTML:

Razor code blocks

Razor code blocks start with @ and are enclosed by {}. Unlike expressions, C# code inside code blocks isn't rendered. Code blocks and expressions in a view share the same scope and are defined in order:

The code renders the following HTML:

In code blocks, declare local functions with markup to serve as templating methods:

The code renders the following HTML:

Implicit transitions

The default language in a code block is C#, but the Razor Page can transition back to HTML:

Explicit delimited transition

To define a subsection of a code block that should render HTML, surround the characters for rendering with the Razor <text> tag:

Use this approach to render HTML that isn't surrounded by an HTML tag. Without an HTML or Razor tag, a Razor runtime error occurs.

Git Markup Syntax

The <text> tag is useful to control whitespace when rendering content:

  • Only the content between the <text> tag is rendered.
  • No whitespace before or after the <text> tag appears in the HTML output.

Explicit line transition

To render the rest of an entire line as HTML inside a code block, use @: syntax:

Without the @: in the code, a Razor runtime error is generated.

Extra @ characters in a Razor file can cause compiler errors at statements later in the block. These compiler errors can be difficult to understand because the actual error occurs before the reported error. This error is common after combining multiple implicit/explicit expressions into a single code block.

Control structures

Control structures are an extension of code blocks. All aspects of code blocks (transitioning to markup, inline C#) also apply to the following structures:

Conditionals @if, else if, else, and @switch

@if controls when code runs:

else and else if don't require the @ symbol:

The following markup shows how to use a switch statement:

Looping @for, @foreach, @while, and @do while

Templated HTML can be rendered with looping control statements. To render a list of people:

The following looping statements are supported:

@for

@foreach

@while

@do while

Compound @using

In C#, a using statement is used to ensure an object is disposed. In Razor, the same mechanism is used to create HTML Helpers that contain additional content. In the following code, HTML Helpers render a <form> tag with the @using statement:

@try, catch, finally

Exception handling is similar to C#:

@lock

Razor has the capability to protect critical sections with lock statements:

Razor supports C# and HTML comments:

The code renders the following HTML:

Razor comments are removed by the server before the webpage is rendered. Razor uses @* *@ to delimit comments. The following code is commented out, so the server doesn't render any markup:

Directives

Razor directives are represented by implicit expressions with reserved keywords following the @ symbol. A directive typically changes the way a view is parsed or enables different functionality.

Understanding how Razor generates code for a view makes it easier to understand how directives work.

The code generates a class similar to the following:

Later in this article, the section Inspect the Razor C# class generated for a view explains how to view this generated class.

@attribute

The @attribute directive adds the given attribute to the class of the generated page or view. The following example adds the [Authorize] attribute:

@code

This scenario only applies to Razor components (.razor).

The @code block enables a Razor component to add C# members (fields, properties, and methods) to a component:

For Razor components, @code is an alias of @functions and recommended over @functions. More than one @code block is permissible.

@functions

The @functions directive enables adding C# members (fields, properties, and methods) to the generated class:

In Razor components, use @code over @functions to add C# members.

For example:

The code generates the following HTML markup:

Markup language syntax

The following code is the generated Razor C# class:

@functions methods serve as templating methods when they have markup:

The code renders the following HTML:

@implements

The @implements directive implements an interface for the generated class.

The following example implements System.IDisposable so that the Dispose method can be called:

@inherits

The @inherits directive provides full control of the class the view inherits:

The following code is a custom Razor page type:

The CustomText is displayed in a view:

The code renders the following HTML:

@model and @inherits can be used in the same view. @inherits can be in a _ViewImports.cshtml file that the view imports:

The following code is an example of a strongly-typed view:

If '[email protected]' is passed in the model, the view generates the following HTML markup:

@inject

The @inject directive enables the Razor Page to inject a service from the service container into a view. For more information, see Dependency injection into views.

@layout

Markup Language Syntax

This scenario only applies to Razor components (.razor).

The @layout directive specifies a layout for routable Razor components that have an @page directive. Layout components are used to avoid code duplication and inconsistency. For more information, see ASP.NET Core Blazor layouts.

@model

This scenario only applies to MVC views and Razor Pages (.cshtml).

The @model directive specifies the type of the model passed to a view or page:

In an ASP.NET Core MVC or Razor Pages app created with individual user accounts, Views/Account/Login.cshtml contains the following model declaration:

The class generated inherits from RazorPage<dynamic>:

Razor exposes a Model property for accessing the model passed to the view:

The @model directive specifies the type of the Model property. The directive specifies the T in RazorPage<T> that the generated class that the view derives from. If the @model directive isn't specified, the Model property is of type dynamic. For more information, see Strongly typed models and the @model keyword.

@namespace

The @namespace directive:

  • Sets the namespace of the class of the generated Razor page, MVC view, or Razor component.
  • Sets the root derived namespaces of a pages, views, or components classes from the closest imports file in the directory tree, _ViewImports.cshtml (views or pages) or _Imports.razor (Razor components).

For the Razor Pages example shown in the following table:

  • Each page imports Pages/_ViewImports.cshtml.
  • Pages/_ViewImports.cshtml contains @namespace Hello.World.
  • Each page has Hello.World as the root of it's namespace.
PageNamespace
Pages/Index.cshtmlHello.World
Pages/MorePages/Page.cshtmlHello.World.MorePages
Pages/MorePages/EvenMorePages/Page.cshtmlHello.World.MorePages.EvenMorePages

The preceding relationships apply to import files used with MVC views and Razor components.

When multiple import files have a @namespace directive, the file closest to the page, view, or component in the directory tree is used to set the root namespace.

If the EvenMorePages folder in the preceding example has an imports file with @namespace Another.Planet (or the Pages/MorePages/EvenMorePages/Page.cshtml file contains @namespace Another.Planet), the result is shown in the following table.

PageNamespace
Pages/Index.cshtmlHello.World
Pages/MorePages/Page.cshtmlHello.World.MorePages
Pages/MorePages/EvenMorePages/Page.cshtmlAnother.Planet

@page

The @page directive has different effects depending on the type of the file where it appears. The directive:

  • In a .cshtml file indicates that the file is a Razor Page. For more information, see Custom routes and Introduction to Razor Pages in ASP.NET Core.
  • Specifies that a Razor component should handle requests directly. For more information, see ASP.NET Core Blazor routing.

The @page directive on the first line of a .cshtml file indicates that the file is a Razor Page. For more information, see Introduction to Razor Pages in ASP.NET Core.

@preservewhitespace

This scenario only applies to Razor components (.razor).

When set to false (default), whitespace in the rendered markup from Razor components (.razor) is removed if:

  • Leading or trailing within an element.
  • Leading or trailing within a RenderFragment parameter. For example, child content passed to another component.
  • It precedes or follows a C# code block, such as @if or @foreach.

@section

This scenario only applies to MVC views and Razor Pages (.cshtml).

The @section directive is used in conjunction with MVC and Razor Pages layouts to enable views or pages to render content in different parts of the HTML page. For more information, see Layout in ASP.NET Core.

@using

The @using directive adds the C# using directive to the generated view:

In Razor components, @using also controls which components are in scope.

Directive attributes

Razor directive attributes are represented by implicit expressions with reserved keywords following the @ symbol. A directive attribute typically changes the way an element is parsed or enables different functionality.

@attributes

This scenario only applies to Razor components (.razor).

@attributes allows a component to render non-declared attributes. For more information, see ASP.NET Core Razor components.

@bind

This scenario only applies to Razor components (.razor).

Data binding in components is accomplished with the @bind attribute. For more information, see ASP.NET Core Blazor data binding.

@on{EVENT}

This scenario only applies to Razor components (.razor).

Razor provides event handling features for components. For more information, see ASP.NET Core Blazor event handling.

@on{EVENT}:preventDefault

Markup Syntax

This scenario only applies to Razor components (.razor).

Prevents the default action for the event.

@on{EVENT}:stopPropagation

This scenario only applies to Razor components (.razor).

Stops event propagation for the event.

@key

This scenario only applies to Razor components (.razor).

The @key directive attribute causes the components diffing algorithm to guarantee preservation of elements or components based on the key's value. For more information, see ASP.NET Core Razor components.

@ref

This scenario only applies to Razor components (.razor).

Component references (@ref) provide a way to reference a component instance so that you can issue commands to that instance. For more information, see ASP.NET Core Razor components.

@typeparam

This scenario only applies to Razor components (.razor).

The @typeparam directive declares a generic type parameter for the generated component class. For more information, see ASP.NET Core Blazor templated components.

Templated Razor delegates

Razor templates allow you to define a UI snippet with the following format:

The following example illustrates how to specify a templated Razor delegate as a Func<T,TResult>. The dynamic type is specified for the parameter of the method that the delegate encapsulates. An object type is specified as the return value of the delegate. The template is used with a List<T> of Pet that has a Name property.

The template is rendered with pets supplied by a foreach statement:

Rendered output:

You can also supply an inline Razor template as an argument to a method. In the following example, the Repeat method receives a Razor template. The method uses the template to produce HTML content with repeats of items supplied from a list:

Using the list of pets from the prior example, the Repeat method is called with:

  • List<T> of Pet.
  • Number of times to repeat each pet.
  • Inline template to use for the list items of an unordered list.

Rendered output:

Tag Helpers

This scenario only applies to MVC views and Razor Pages (.cshtml).

There are three directives that pertain to Tag Helpers.

DirectiveFunction
@addTagHelperMakes Tag Helpers available to a view.
@removeTagHelperRemoves Tag Helpers previously added from a view.
@tagHelperPrefixSpecifies a tag prefix to enable Tag Helper support and to make Tag Helper usage explicit.

Razor reserved keywords

Razor keywords

  • page (Requires ASP.NET Core 2.1 or later)
  • namespace
  • functions
  • inherits
  • model
  • section
  • helper (Not currently supported by ASP.NET Core)

Razor keywords are escaped with @(Razor Keyword) (for example, @(functions)).

C# Razor keywords

  • case
  • do
  • default
  • for
  • foreach
  • if
  • else
  • lock
  • switch
  • try
  • catch
  • finally
  • using
  • while

C# Razor keywords must be double-escaped with @(@C# Razor Keyword) (for example, @(@case)). The first @ escapes the Razor parser. The second @ escapes the C# parser.

Reserved keywords not used by Razor

  • class

Inspect the Razor C# class generated for a view

With .NET Core SDK 2.1 or later, the Razor SDK handles compilation of Razor files. When building a project, the Razor SDK generates an obj/<build_configuration>/<target_framework_moniker>/Razor directory in the project root. The directory structure within the Razor directory mirrors the project's directory structure.

Consider the following directory structure in an ASP.NET Core 2.1 Razor Pages project targeting .NET Core 2.1:

Building the project in Debug configuration yields the following obj directory:

To view the generated class for Pages/Index.cshtml, open obj/Debug/netcoreapp2.1/Razor/Pages/Index.g.cshtml.cs.

Add the following class to the ASP.NET Core MVC project:

In Startup.ConfigureServices, override the RazorTemplateEngine added by MVC with the CustomTemplateEngine class:

Set a breakpoint on the return csharpDocument; statement of CustomTemplateEngine. When program execution stops at the breakpoint, view the value of generatedCode.

View lookups and case sensitivity

The Razor view engine performs case-sensitive lookups for views. However, the actual lookup is determined by the underlying file system:

  • File based source:
    • On operating systems with case insensitive file systems (for example, Windows), physical file provider lookups are case insensitive. For example, return View('Test') results in matches for /Views/Home/Test.cshtml, /Views/home/test.cshtml, and any other casing variant.
    • On case-sensitive file systems (for example, Linux, OSX, and with EmbeddedFileProvider), lookups are case-sensitive. For example, return View('Test') specifically matches /Views/Home/Test.cshtml.
  • Precompiled views: With ASP.NET Core 2.0 and later, looking up precompiled views is case insensitive on all operating systems. The behavior is identical to physical file provider's behavior on Windows. If two precompiled views differ only in case, the result of lookup is non-deterministic.

Developers are encouraged to match the casing of file and directory names to the casing of:

  • Area, controller, and action names.
  • Razor Pages.

Matching case ensures the deployments find their views regardless of the underlying file system.

Additional resources

Introduction to ASP.NET Web Programming Using the Razor Syntax provides many samples of programming with Razor syntax.