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Introduction to Razor Pages in ASP.NET Core Rick-Anderson Overview of Razor Pages in ASP.NET Core ASP.NET Core, Razor Pages riande wpickett 08/15/2017 get-started-article aspnet asp.net-core mvc/razor-pages/index

Introduction to Razor Pages in ASP.NET Core

By Rick Anderson and Ryan Nowak

Razor Pages is a new feature of ASP.NET Core MVC that makes coding page-focused scenarios easier and more productive.

If you're looking for a tutorial that uses the Model-View-Controller approach, see Getting started with ASP.NET Core MVC.

ASP.NET Core 2.0 prerequisites

Install .NET Core 2.0.0 or later.

If you're using Visual Studio, install Visual Studio 15.3 or later with the following workloads:

  • ASP.NET and web development
  • .NET Core cross-platform development

Creating a Razor Pages project

Visual Studio

See Getting started with Razor Pages for detailed instructions on how to create a Razor Pages project using Visual Studio.

Visual Studio for Mac

Run dotnet new razor from the command line.

Open the generated .csproj file from Visual Studio for Mac.

Visual Studio Code

Run dotnet new razor from the command line.

.NET Core CLI

Run dotnet new razor from the command line.

Razor Pages

Razor Pages is enabled in Startup.cs:

[!code-csmain]

Consider a basic page:

[!code-cshtmlmain]

The preceding code looks a lot like a Razor view file. What makes it different is the @page directive. @page makes the file into an MVC action - which means that it handles requests directly, without going through a controller. @page must be the first Razor directive on a page. @page affects the behavior of other Razor constructs. The @functions directive enables function-level content.

A similar page, with the PageModel in a separate file, is shown in the following two files. The Pages/Index2.cshtml file:

[!code-cshtmlmain]

The Pages/Index2.cshtml.cs 'code-behind' file:

[!code-csmain]

By convention, the PageModel class file has the same name as the Razor Page file with .cs appended. For example, the previous Razor Page is Pages/Index2.cshtml. The file containing the PageModel class is named Pages/Index2.cshtml.cs.

For simple pages, mixing the PageModel class with the Razor markup is fine. For more complex code, it's a best practice to keep the page model code separate.

The associations of URL paths to pages are determined by the page's location in the file system. The following table shows a Razor Page path and the matching URL:

File name and path matching URL
/Pages/Index.cshtml / or /Index
/Pages/Contact.cshtml /Contact
/Pages/Store/Contact.cshtml /Store/Contact
/Pages/Store/Index.cshtml /Store or /Store/Index

Notes:

  • The runtime looks for Razor Pages files in the Pages folder by default.
  • Index is the default page when a URL doesn't include a page.

Writing a basic form

Razor Pages features are designed to make common patterns used with web browsers easy. Model binding, Tag Helpers, and HTML helpers all just work with the properties defined in a Razor Page class. Consider a page that implements a basic "contact us" form for the Contact model:

For the samples in this document, the DbContext is initialized in the Startup.cs file.

[!code-csmain]

The data model:

[!code-csmain]

The Pages/Create.cshtml view file:

[!code-cshtmlmain]

The Pages/Create.cshtml.cs code-behind file for the view:

[!code-csmain]

By convention, the PageModel class is called <PageName>Model and is in the same namespace as the page. Not much change is needed to convert from a page using @functions to define handlers and a page using a PageModel class.

Using a PageModel code-behind file supports unit testing, but requires you to write an explicit constructor and class. Pages without PageModel code-behind files support runtime compilation, which can be an advantage in development.

The page has an OnPostAsync handler method which runs on POST requests (when a user posts the form). You can add handler methods for any HTTP verb. The most common handlers are:

  • OnGet to initialize state needed for the page. OnGet sample.
  • OnPost to handle form submissions.

The Async naming suffix is optional but is often used by convention for asynchronous functions. The OnPostAsync code in the preceding example looks similar to what you would normally write in a controller. This is typical for Razor Pages. Most of the MVC primitives like model binding, validation, and action results are shared.

The previous OnPostAsync method:

[!code-csmain]

The basic flow of OnPostAsync:

Check for validation errors.

  • If there are no errors, save the data and redirect.
  • If there are errors, show the page again with validation messages. Client-side validation is identical to traditional ASP.NET Core MVC applications. In many cases, validation errors would be caught on the client and never submitted to the server.

When the data is entered successfully, the OnPostAsync handler method calls the RedirectToPage helper method to return an instance of RedirectToPageResult. This is a new action result, similar to RedirectToAction or RedirectToRoute, but customized for pages. In the preceding sample, it redirects to the root Index page (/Index). RedirectToPage is detailed in the URL generation for Pages section.

When the submitted form has validation errors (that are passed to the server), theOnPostAsync handler method calls the Page helper method. Page returns an instance of PageResult. This is similar to how actions in controllers return View. PageResult is the default return type for a handler method. A handler method that returns void will render the page.

The Customer property uses [BindProperty] attribute to opt-in to model binding.

[!code-csmain]

Razor Pages, by default, bind properties only with non-GET verbs. Binding to properties can reduce the amount of code you have to write by using the same property to render form fields (<input asp-for="Customer.Name" />) and accept the input.

The following code shows the combined version of the create page:

[!code-cshtmlmain]

Rather than using @model, we're taking advantage of a new feature for Pages. By default, the generated Page-derived class is the model. Using a view model with Razor views is a best practice. With Pages, you get a view model automatically.

The main change is replacing constructor injection with injected (@inject) properties. This page uses @inject for constructor dependency injection. The @inject statement generates and initializes the Db property that is used in OnPostAsync. Injected (@inject) properties are set before handler methods run.

The home page (Index.cshtml):

[!code-cshtmlmain]

The code behind Index.cshtml.cs file:

[!code-csmain]

The Index.cshtml file contains the following markup to create an edit link for each contact:

<a asp-page="./Edit" asp-route-id="@contact.Id">edit</a>

The Anchor Tag Helper used the asp-route-{value} attribute to generate a link to the Edit page. The link contains route data with the contact ID. For example, http://localhost:5000/Edit/1.

The Pages/Edit.cshtml file:

[!code-cshtmlmain]

The first line contains the @page "{id:int}" directive. The routing constraint"{id:int}" tells the page to accept requests to the page that contain int route data. If a request to the page doesn't contain route data that can be converted to an int, the runtime returns an HTTP 404 (not found) error.

The Pages/Edit.cshtml.cs file:

[!code-csmain]

XSRF/CSRF and Razor Pages

You don't have to write any code for antiforgery validation. Antiforgery token generation and validation is automatically included in Razor Pages.

Using Layouts, partials, templates, and Tag Helpers with Razor Pages

Pages work with all the features of the Razor view engine. Layouts, partials, templates, Tag Helpers, _ViewStart.cshtml, _ViewImports.cshtml work in the same way they do for conventional Razor views.

Let's declutter this page by taking advantage of some of those features.

Add a layout page to Pages/_Layout.cshtml:

[!code-cshtmlmain]

The Layout:

  • Controls the layout of each page (unless the page opts out of layout).
  • Imports HTML structures such as JavaScript and stylesheets.

See layout page for more information.

The Layout property is set in Pages/_ViewStart.cshtml:

[!code-cshtmlmain]

Note: The layout is in the Pages folder. Pages look for other views (layouts, templates, partials) hierarchically, starting in the same folder as the current page. This means that a layout in the Pages folder can be used from any Razor page under the Pages folder.

We recommend you not put the layout file in the Views/Shared folder. Views/Shared is an MVC views pattern. Razor Pages are meant to rely on folder hierarchy, not path conventions.

View search from a Razor Page will include the Pages folder. The layouts, templates, and partials you're using with MVC controllers and conventional Razor views just work.

Add a Pages/_ViewImports.cshtml file:

[!code-cshtmlmain]

I'll explain the @namespace later. The @addTagHelper directive will bring in the built-in Tag Helpers to all the pages in the Pages folder.

When the @namespace directive is used explicitly on a page:

[!code-cshtmlmain]

The directive sets the namespace for the page. The @model directive doesn't need to include the namespace.

When the @namespace directive is contained in _ViewImports.cshtml, the specified namespace supplies the prefix for the generated namespace in the Page that imports the @namespace directive. The rest of the generated namespace (the suffix portion) is the dot-separated relative path between the folder containing _ViewImports.cshtml and the folder containing the page.

For example, the code behind file Pages/Customers/Edit.cshtml.cs explicitly sets the namespace:

[!code-csmain]

The Pages/_ViewImports.cshtml file sets the following namespace:

[!code-cshtmlmain]

The generated namespace for the Pages/Customers/Edit.cshtml Razor Page is the same as the code behind file. The @namespace directive was designed so the C# classes you add and pages-generated code just work without having to add an @using directive for the code behind file.

Note: @namespace also works with conventional Razor views.

The original Pages/Create.cshtml view file:

[!code-cshtmlmain]

The updated page:

The Pages/Create.cshtml view file:

[!code-cshtmlmain]

The Razor Pages starter project contains the Pages/_ValidationScriptsPartial.cshtml, which hooks up client side validation.

URL generation for Pages

The Create page, shown previously, uses RedirectToPage:

[!code-csmain]

The app has the following file/folder structure

  • /Pages

    • Index.cshtml

    • /Customer

      • Create.cshtml
      • Edit.cshtml
      • Index.cshtml

The Pages/Customers/Create.cshtml and Pages/Customers/Edit.cshtml pages redirect to Pages/Index.cshtml after success. The string /Index is part of the URI to access the preceding page. The string /Index can be used to generate URIs to the Pages/Index.cshtml page. For example:

  • Url.Page("/Index", ...)
  • <a asp-page="/Index">My Index Page</a>
  • RedirectToPage("/Index")

The page name is the path to the page from the root /Pages folder (including a leading /, for example /Index). This is much more feature-rich than just hardcoding a URL. This is URL generation using routing, and can generate and encode parameters according to how the route is defined in the destination path.

URL generation for pages supports relative names. The following table shows which Index page is selected with different RedirectToPage parameters from Pages/Customers/Create.cshtml:

RedirectToPage(x) Page
RedirectToPage("/Index") Pages/Index
RedirectToPage("./Index"); Pages/Customers/Index
RedirectToPage("../Index") Pages/Index
RedirectToPage("Index") Pages/Customers/Index

RedirectToPage("Index"), RedirectToPage("./Index"), and RedirectToPage("../Index") are relative names. The RedirectToPage parameter is combined with the path of the current page to compute the name of the destination page. <!-- Review: Original had The provided string is combined with the page name of the current page to compute the name of the destination page. -- page name, not page path -->

Relative name linking is useful when building sites with a complex structure. If you use relative names to link between pages in a folder, you can rename that folder. All the links still work (because they didn't include the folder name).

TempData

ASP.NET Core exposes the TempData property on a controller. This property stores data until it is read. The Keep and Peek methods can be used to examine the data without deletion. TempData is particularly useful for redirection, when data is needed for more than a single request.

The [TempData] attribute is new in ASP.NET Core 2.0 and is supported on controllers and pages.

The following code sets the value of Message using TempData. [!code-csmain]

The following markup in the Pages/Customers/Index.cshtml file displays the value of Message using TempData.

<h3>Msg: @Model.Message</h3>

The Pages/Customers/Index.cshtml.cs code-behind file applies the [TempData] attribute to the Message property.

[TempData]
public string Message { get; set; }

See TempData for more information.

Multiple handlers per page

The following page generates markup for two page handlers using the asp-page-handler Tag Helper:

[!code-cshtmlmain]

The form in the preceding example has two submit buttons, each using the FormActionTagHelper to submit to a different URL. The asp-page-handler attribute is a companion to asp-page. asp-page-handler generates URLs that submit to each of the handler methods defined by a page. asp-page is not specified because the sample is linking to the current page.

The code-behind file:

[!code-csmain]

The preceding code uses named handler methods. Named handler methods are created by taking the text in the name after On<HTTP Verb> and before Async (if present). In the preceding example, the page methods are OnPostJoinListAsync and OnPostJoinListUCAsync. With OnPost and Async removed, the handler names are JoinList and JoinListUC.

[!code-cshtmlmain]

Using the preceding code, the URL path that submits to OnPostJoinListAsync is http://localhost:5000/Customers/CreateFATH?handler=JoinList. The URL path that submits to OnPostJoinListUCAsync is http://localhost:5000/Customers/CreateFATH?handler=JoinListUC.

Customizing Routing

If you don't like the query string ?handler=JoinList in the URL, you can change the route to put the handler name in the path portion of the URL. You can customize the route by adding a route template enclosed in double quotes after the @page directive.

[!code-cshtmlmain]

This route will now put the handler name in the URL path instead of the query string. The ? following handler means this is an optional route parameter.

You can use @page to add additional segments and parameters to a page's route. Whatever's there is appended to the default route of the page. Using an absolute or virtual path to change the page's route (like "~/Some/Other/Path") is not supported.

Configuration and settings

Use the extension method AddRazorPagesOptions on the MVC builder to configure advanced options such as the following example:

public class Startup
{
    public void ConfigureServices(IServiceCollections services)
    {
        services.AddMvc().AddRazorPagesOptions(options =>
        {
           ...
        });
    }

    ...
}

Currently you can use the RazorPagesOptions to set the root directory for pages, or add application model conventions for pages. We hope to enable more extensibility this way in the future.

See Razor view compilation to precompile views.

Download or view sample code.

See Getting started with Razor Pages in ASP.NET Core, which builds on this tutorial.