Razor syntax reference for ASP.NET Core

By Rick Anderson, Taylor Mullen, and Dan Vicarel

Razor is a markup syntax for embedding .NET 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 component files (.razor). Razor syntax is similar to the templating engines of various JavaScript single-page application (SPA) frameworks, such as Angular, React, VueJs, and Svelte. For more information see, The features described in this article are obsolete as of ASP.NET Core 3.0.

Introduction to ASP.NET Web Programming Using the Razor Syntax provides many samples of programming with Razor syntax. Although the topic was written for ASP.NET rather than ASP.NET Core, most of the samples apply to ASP.NET Core.

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 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 HTML.

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

<p>@@Username</p>

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

<p>@Username</p>

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:

<a href="mailto:Support@contoso.com">Support@contoso.com</a>

@{
    string message = "foreignObject example with Scalable Vector Graphics (SVG)";
}

<svg width="200" height="200" xmlns="http://www.w3.org/2000/svg">
    <rect x="0" y="0" rx="10" ry="10" width="200" height="200" stroke="black" 
        fill="none" />
    <foreignObject x="20" y="20" width="160" height="160">
        <p>@message</p>
    </foreignObject>
</svg>

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

<p>@DateTime.Now</p>
<p>@DateTime.IsLeapYear(2016)</p>

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:

<p>@await DoSomething("hello", "world")</p>

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

<p>@GenericMethod<int>()</p>

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

<p>Last week this time: @(DateTime.Now - TimeSpan.FromDays(7))</p>

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:

<p>Last week: @DateTime.Now - TimeSpan.FromDays(7)</p>

The code renders the following HTML:

<p>Last week: 7/7/2016 4:39:52 PM - TimeSpan.FromDays(7)</p>

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

@{
    var joe = new Person("Joe", 33);
}

<p>Age@(joe.Age)</p>

Without the explicit expression, <p>Age@joe.Age</p> is treated as an email address, and <p>Age@joe.Age</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:

<p>@(GenericMethod<int>())</p>

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.

@("<span>Hello World</span>")

The preceding code renders the following HTML:

<span>Hello World</span>

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.

@Html.Raw("<span>Hello World</span>")

The code renders the following HTML:

<span>Hello World</span>

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:

@{
    var quote = "The future depends on what you do today. - Mahatma Gandhi";
}

<p>@quote</p>

@{
    quote = "Hate cannot drive out hate, only love can do that. - Martin Luther King, Jr.";
}

<p>@quote</p>

The code renders the following HTML:

<p>The future depends on what you do today. - Mahatma Gandhi</p>
<p>Hate cannot drive out hate, only love can do that. - Martin Luther King, Jr.</p>

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

@{
    void RenderName(string name)
    {
        <p>Name: <strong>@name</strong></p>
    }

    RenderName("Mahatma Gandhi");
    RenderName("Martin Luther King, Jr.");
}

The code renders the following HTML:

<p>Name: <strong>Mahatma Gandhi</strong></p>
<p>Name: <strong>Martin Luther King, Jr.</strong></p>

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

@{
    var inCSharp = true;
    <p>Now in HTML, was in C# @inCSharp</p>
}

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

@for (var i = 0; i < people.Length; i++)
{
    var person = people[i];
    <text>Name: @person.Name</text>
}

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.

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.

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

@for (var i = 0; i < people.Length; i++)
{
    var person = people[i];
    @:Name: @person.Name
}

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 extra @ compiler errors:

• Can be difficult to understand because the actual error occurs before the reported error.
• Is common after combining multiple implicit and explicit expressions into a single code block.

Razor automatically omits attributes that aren't needed. If the value passed in is null or false, the attribute isn't rendered.

For example, consider the following razor:

<div class="@false">False</div>
<div class="@null">Null</div>
<div class="@("")">Empty</div>
<div class="@("false")">False String</div>
<div class="@("active")">String</div>
<input type="checkbox" checked="@true" name="true" />
<input type="checkbox" checked="@false" name="false" />
<input type="checkbox" checked="@null" name="null" />

The preceding Razor markup generates the following HTML:

<div>False</div>
<div>Null</div>
<div class="">Empty</div>
<div class="false">False String</div>
<div class="active">String</div>
<input type="checkbox" checked="checked" name="true">
<input type="checkbox" name="false">
<input type="checkbox" name="null">

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

@if controls when code runs:

@if (value % 2 == 0)
{
    <p>The value was even.</p>
}

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

@if (value % 2 == 0)
{
    <p>The value was even.</p>
}
else if (value >= 1337)
{
    <p>The value is large.</p>
}
else
{
    <p>The value is odd and small.</p>
}

The following markup shows how to use a switch statement:

@switch (value)
{
    case 1:
        <p>The value is 1!</p>
        break;
    case 1337:
        <p>Your number is 1337!</p>
        break;
    default:
        <p>Your number wasn't 1 or 1337.</p>
        break;
}

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

@{
    var people = new Person[]
    {
          new Person("Weston", 33),
          new Person("Johnathon", 41),
          ...
    };
}

The following looping statements are supported:

@for

@for (var i = 0; i < people.Length; i++)
{
    var person = people[i];
    <p>Name: @person.Name</p>
    <p>Age: @person.Age</p>
}

@foreach

@foreach (var person in people)
{
    <p>Name: @person.Name</p>
    <p>Age: @person.Age</p>
}

@while

@{ var i = 0; }
@while (i < people.Length)
{
    var person = people[i];
    <p>Name: @person.Name</p>
    <p>Age: @person.Age</p>

    i++;
}

@do while

@{ var i = 0; }
@do
{
    var person = people[i];
    <p>Name: @person.Name</p>
    <p>Age: @person.Age</p>

    i++;
} while (i < people.Length);

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:

@using (Html.BeginForm())
{
    <div>
        <label>Email: <input type="email" id="Email" value=""></label>
        <button>Register</button>
    </div>
}

Exception handling is similar to C#:

@try
{
    throw new InvalidOperationException("You did something invalid.");
}
catch (Exception ex)
{
    <p>The exception message: @ex.Message</p>
}
finally
{
    <p>The finally statement.</p>
}

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

@lock (SomeLock)
{
    // Do critical section work
}

Razor supports C# and HTML comments:

@{
    /* C# comment */
    // Another C# comment
}
<!-- HTML comment -->

The code renders the following HTML:

<!-- HTML comment -->

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:

@*
    @{
        /* C# comment */
        // Another C# comment
    }
    <!-- HTML comment -->
*@

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

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

@{
    var quote = "Getting old ain't for wimps! - Anonymous";
}

<div>Quote of the Day: @quote</div>

The code generates a class similar to the following:

public class _Views_Something_cshtml : RazorPage<dynamic>
{
    public override async Task ExecuteAsync()
    {
        var output = "Getting old ain't for wimps! - Anonymous";

        WriteLiteral("/r/n<div>Quote of the Day: ");
        Write(output);
        WriteLiteral("</div>");
    }
}

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

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

@attribute [Authorize]

The @attribute directive can also be used to supply a constant-based route template in a Razor component. In the following example, the @page directive in a component is replaced with the @attribute directive and the constant-based route template in Constants.CounterRoute, which is set elsewhere in the app to "/counter":

- @page "/counter"
+ @attribute [Route(Constants.CounterRoute)]

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:

@code {
    // C# members (fields, properties, and methods)
}

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

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

@functions {
    // C# members (fields, properties, and methods)
}

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

For example:

@functions {
    public string GetHello()
    {
        return "Hello";
    }
}

<div>From method: @GetHello()</div> 

The code generates the following HTML markup:

<div>From method: Hello</div>

The following code is the generated Razor C# class:

using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc.Razor;

public class _Views_Home_Test_cshtml : RazorPage<dynamic>
{
    // Functions placed between here 
    public string GetHello()
    {
        return "Hello";
    }
    // And here.
#pragma warning disable 1998
    public override async Task ExecuteAsync()
    {
        WriteLiteral("\r\n<div>From method: ");
        Write(GetHello());
        WriteLiteral("</div>\r\n");
    }
#pragma warning restore 1998

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

@{
    RenderName("Mahatma Gandhi");
    RenderName("Martin Luther King, Jr.");
}

@functions {
    private void RenderName(string name)
    {
        <p>Name: <strong>@name</strong></p>
    }
}

The code renders the following HTML:

<p>Name: <strong>Mahatma Gandhi</strong></p>
<p>Name: <strong>Martin Luther King, Jr.</strong></p>

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

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

@implements IDisposable

<h1>Example</h1>

@functions {
    private bool _isDisposed;

    ...

    public void Dispose() => _isDisposed = true;
}

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

@inherits TypeNameOfClassToInheritFrom

The following code is a custom Razor page type:

using Microsoft.AspNetCore.Mvc.Razor;

public abstract class CustomRazorPage<TModel> : RazorPage<TModel>
{
    public string CustomText { get; } = 
        "Gardyloo! - A Scottish warning yelled from a window before dumping" +
        "a slop bucket on the street below.";
}

The CustomText is displayed in a view:

@inherits CustomRazorPage<TModel>

<div>Custom text: @CustomText</div>

The code renders the following HTML:

<div>
    Custom text: Gardyloo! - A Scottish warning yelled from a window before dumping
    a slop bucket on the street below.
</div>

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

@inherits CustomRazorPage<TModel>

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

@inherits CustomRazorPage<TModel>

<div>The Login Email: @Model.Email</div>
<div>Custom text: @CustomText</div>

If "rick@contoso.com" is passed in the model, the view generates the following HTML markup:

<div>The Login Email: rick@contoso.com</div>
<div>
    Custom text: Gardyloo! - A Scottish warning yelled from a window before dumping
    a slop bucket on the street below.
</div>

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.

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.

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:

@model TypeNameOfModel

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

@model LoginViewModel

The class generated inherits from RazorPage<LoginViewModel>:

public class _Views_Account_Login_cshtml : RazorPage<LoginViewModel>

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

<div>The Login Email: @Model.Email</div>

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.

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).

@namespace Your.Namespace.Here

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.

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.

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 and navigation.

<... @rendermode="InteractiveServer" />

@rendermode InteractiveServer

@using static Microsoft.AspNetCore.Components.Web.RenderMode

<Dialog @rendermode="RenderMode.InteractiveServer" />

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.

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

The @typeparam directive declares a generic type parameter for the generated component class:

@typeparam TEntity

@typeparam TEntity where TEntity : IEntity

For more information, see the following articles:

• ASP.NET Core Razor component generic type support
• ASP.NET Core Blazor templated components

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

@using System.IO
@{
    var dir = Directory.GetCurrentDirectory();
}
<p>@dir</p>

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

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

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

@attributes allows a component to render non-declared attributes. For more information, see ASP.NET Core Blazor attribute splatting and arbitrary parameters.

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.

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

Use the @bind:culture attribute with the @bind attribute to provide a System.Globalization.CultureInfo for parsing and formatting a value. For more information, see ASP.NET Core Blazor globalization and localization.

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.

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

Prevents the default action for the event.

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

Stops event propagation for the event.

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 Retain element, component, and model relationships in ASP.NET Core Blazor.

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.

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

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

@<tag>...</tag>

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.

public class Pet
{
    public string Name { get; set; }
}

@{
    Func<dynamic, object> petTemplate = @<p>You have a pet named <strong>@item.Name</strong>.</p>;

    var pets = new List<Pet>
    {
        new Pet { Name = "Rin Tin Tin" },
        new Pet { Name = "Mr. Bigglesworth" },
        new Pet { Name = "K-9" }
    };
}

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

@foreach (var pet in pets)
{
    @petTemplate(pet)
}

Rendered output:

<p>You have a pet named <strong>Rin Tin Tin</strong>.</p>
<p>You have a pet named <strong>Mr. Bigglesworth</strong>.</p>
<p>You have a pet named <strong>K-9</strong>.</p>

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 Microsoft.AspNetCore.Html

@functions {
    public static IHtmlContent Repeat(IEnumerable<dynamic> items, int times,
        Func<dynamic, IHtmlContent> template)
    {
        var html = new HtmlContentBuilder();

        foreach (var item in items)
        {
            for (var i = 0; i < times; i++)
            {
                html.AppendHtml(template(item));
            }
        }

        return html;
    }
}

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.

<ul>
    @Repeat(pets, 3, @<li>@item.Name</li>)
</ul>

Rendered output:

<ul>
    <li>Rin Tin Tin</li>
    <li>Rin Tin Tin</li>
    <li>Rin Tin Tin</li>
    <li>Mr. Bigglesworth</li>
    <li>Mr. Bigglesworth</li>
    <li>Mr. Bigglesworth</li>
    <li>K-9</li>
    <li>K-9</li>
    <li>K-9</li>
</ul>

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

There are three directives that pertain to Tag Helpers.

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

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

• 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.

• class

<PropertyGroup>
  <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>
</PropertyGroup>

 Areas/
   Admin/
     Pages/
       Index.cshtml
       Index.cshtml.cs
 Pages/
   Shared/
     _Layout.cshtml
   _ViewImports.cshtml
   _ViewStart.cshtml
   Index.cshtml
   Index.cshtml.cs

 obj/
   Debug/
     netcoreapp2.1/
       Razor/
         Areas/
           Admin/
             Pages/
               Index.g.cshtml.cs
         Pages/
           Shared/
             _Layout.g.cshtml.cs
           _ViewImports.g.cshtml.cs
           _ViewStart.g.cshtml.cs
           Index.g.cshtml.cs

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.

The following imports are generated by the ASP.NET Core web templates to support Razor Files:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewFeatures;

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