AspNetCore.Docs/aspnetcore/razor-pages/razor-pages-conventions.md

title	author	description	monikerRange	ms.author	ms.date	uid
Razor Pages route and app conventions in ASP.NET Core	guardrex	Discover how route and app model provider conventions help you control page routing, discovery, and processing.	>= aspnetcore-2.0	riande	04/12/2018	razor-pages/razor-pages-conventions

Razor Pages route and app conventions in ASP.NET Core

By Luke Latham

Learn how to use page route and app model provider conventions to control page routing, discovery, and processing in Razor Pages apps.

When you need to configure custom page routes for individual pages, configure routing to pages with the AddPageRoute convention described later in this topic.

To specify a page route, add route segments, or add parameters to a route, use the page's @page directive. For more information, see Custom routes.

There are reserved words that can't be used as route segments or parameter names. For more information, see Routing: Reserved routing names.

View or download sample code (how to download)

::: moniker range="= aspnetcore-2.0"

Scenario	The sample demonstrates ...
Model conventions Conventions.Add IPageRouteModelConvention IPageApplicationModelConvention	Add a route template and header to an app's pages.
Page route action conventions AddFolderRouteModelConvention AddPageRouteModelConvention AddPageRoute	Add a route template to pages in a folder and to a single page.
Page model action conventions AddFolderApplicationModelConvention AddPageApplicationModelConvention ConfigureFilter (filter class, lambda expression, or filter factory)	Add a header to pages in a folder, add a header to a single page, and configure a filter factory to add a header to an app's pages.
Default page app model provider	Replace the default page model provider to change the conventions for handler names.

::: moniker-end

::: moniker range=">= aspnetcore-2.1"

Scenario	The sample demonstrates ...
Model conventions Conventions.Add IPageRouteModelConvention IPageApplicationModelConvention IPageHandlerModelConvention	Add a route template and header to an app's pages.
Page route action conventions AddFolderRouteModelConvention AddPageRouteModelConvention AddPageRoute	Add a route template to pages in a folder and to a single page.
Page model action conventions AddFolderApplicationModelConvention AddPageApplicationModelConvention ConfigureFilter (filter class, lambda expression, or filter factory)	Add a header to pages in a folder, add a header to a single page, and configure a filter factory to add a header to an app's pages.
Default page app model provider	Replace the default page model provider to change the conventions for handler names.

::: moniker-end

Razor Pages conventions are added and configured using the AddRazorPagesOptions extension method to AddMvc on the service collection in the Startup class. The following convention examples are explained later in this topic:

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc()
        .AddRazorPagesOptions(options =>
            {
                options.Conventions.Add( ... );
                options.Conventions.AddFolderRouteModelConvention("/OtherPages", model => { ... });
                options.Conventions.AddPageRouteModelConvention("/About", model => { ... });
                options.Conventions.AddPageRoute("/Contact", "TheContactPage/{text?}");
                options.Conventions.AddFolderApplicationModelConvention("/OtherPages", model => { ... });
                options.Conventions.AddPageApplicationModelConvention("/About", model => { ... });
                options.Conventions.ConfigureFilter(model => { ... });
                options.Conventions.ConfigureFilter( ... );
            });
}

Model conventions

Add a delegate for IPageConvention to add model conventions that apply to Razor Pages.

Add a route model convention to all pages

Use Conventions to create and add an IPageRouteModelConvention to the collection of IPageConvention instances that are applied during page route model construction.

The sample app adds a {globalTemplate?} route template to all of the pages in the app:

[!code-csharp]

[!NOTE] The Order property for the AttributeRouteModel is set to -1. This ensures that this template is given priority for the first route data value position when a single route value is provided and also that it would have priority over automatically generated Razor Pages routes. For example, the sample adds an {aboutTemplate?} route template later in the topic. The {aboutTemplate?} template is given an Order of 1. When the About page is requested at /About/RouteDataValue, "RouteDataValue" is loaded into RouteData.Values["globalTemplate"] (Order = -1) and not RouteData.Values["aboutTemplate"] (Order = 1) due to setting the Order property.

Razor Pages options, such as adding Conventions, are added when MVC is added to the service collection in Startup.ConfigureServices. For an example, see the sample app.

[!code-csharp]

Request the sample's About page at localhost:5000/About/GlobalRouteValue and inspect the result:

Add an app model convention to all pages

Use Conventions to create and add an IPageApplicationModelConvention to the collection of IPageConvention instances that are applied during page app model construction.

To demonstrate this and other conventions later in the topic, the sample app includes an AddHeaderAttribute class. The class constructor accepts a name string and a values string array. These values are used in its OnResultExecuting method to set a response header. The full class is shown in the Page model action conventions section later in the topic.

The sample app uses the AddHeaderAttribute class to add a header, GlobalHeader, to all of the pages in the app:

[!code-csharp]

Startup.cs:

[!code-csharp]

Request the sample's About page at localhost:5000/About and inspect the headers to view the result:

::: moniker range=">= aspnetcore-2.1" Add a handler model convention to all pages

Use Conventions to create and add an IPageHandlerModelConvention to the collection of IPageConvention instances that are applied during page handler model construction.

public class GlobalPageHandlerModelConvention 
    : IPageHandlerModelConvention
{
    public void Apply(PageHandlerModel model)
    {
        ...
    }
}

Startup.ConfigureServices:

services.AddMvc()
    .AddRazorPagesOptions(options =>
        {
            options.Conventions.Add(new GlobalPageHandlerModelConvention());
        });

::: moniker-end

Page route action conventions

The default route model provider that derives from IPageRouteModelProvider invokes conventions which are designed to provide extensibility points for configuring page routes.

Folder route model convention

Use AddFolderRouteModelConvention to create and add an IPageRouteModelConvention that invokes an action on the PageRouteModel for all of the pages under the specified folder.

The sample app uses AddFolderRouteModelConvention to add an {otherPagesTemplate?} route template to the pages in the OtherPages folder:

[!code-csharp]

[!NOTE] The Order property for the AttributeRouteModel is set to 1. This ensures that the template for {globalTemplate?} (set earlier in the topic) is given priority for the first route data value position when a single route value is provided. If the Page1 page is requested at /OtherPages/Page1/RouteDataValue, "RouteDataValue" is loaded into RouteData.Values["globalTemplate"] (Order = -1) and not RouteData.Values["otherPagesTemplate"] (Order = 1) due to setting the Order property.

Request the sample's Page1 page at localhost:5000/OtherPages/Page1/GlobalRouteValue/OtherPagesRouteValue and inspect the result:

Page route model convention

Use AddPageRouteModelConvention to create and add an IPageRouteModelConvention that invokes an action on the PageRouteModel for the page with the specified name.

The sample app uses AddPageRouteModelConvention to add an {aboutTemplate?} route template to the About page:

[!code-csharp]

[!NOTE] The Order property for the AttributeRouteModel is set to 1. This ensures that the template for {globalTemplate?} (set earlier in the topic) is given priority for the first route data value position when a single route value is provided. If the About page is requested at /About/RouteDataValue, "RouteDataValue" is loaded into RouteData.Values["globalTemplate"] (Order = -1) and not RouteData.Values["aboutTemplate"] (Order = 1) due to setting the Order property.

Request the sample's About page at localhost:5000/About/GlobalRouteValue/AboutRouteValue and inspect the result:

Configure a page route

Use AddPageRoute to configure a route to a page at the specified page path. Generated links to the page use your specified route. AddPageRoute uses AddPageRouteModelConvention to establish the route.

The sample app creates a route to /TheContactPage for Contact.cshtml:

[!code-csharp]

The Contact page can also be reached at /Contact via its default route.

The sample app's custom route to the Contact page allows for an optional text route segment ({text?}). The page also includes this optional segment in its @page directive in case the visitor accesses the page at its /Contact route:

[!code-cshtml]

Note that the URL generated for the Contact link in the rendered page reflects the updated route:

Visit the Contact page at either its ordinary route, /Contact, or the custom route, /TheContactPage. If you supply an additional text route segment, the page shows the HTML-encoded segment that you provide:

Page model action conventions

The default page model provider that implements IPageApplicationModelProvider invokes conventions which are designed to provide extensibility points for configuring page models. These conventions are useful when building and modifying page discovery and processing scenarios.

For the examples in this section, the sample app uses an AddHeaderAttribute class, which is a ResultFilterAttribute, that applies a response header:

[!code-csharp]

Using conventions, the sample demonstrates how to apply the attribute to all of the pages in a folder and to a single page.

Folder app model convention

Use AddFolderApplicationModelConvention to create and add an IPageApplicationModelConvention that invokes an action on PageApplicationModel instances for all pages under the specified folder.

The sample demonstrates the use of AddFolderApplicationModelConvention by adding a header, OtherPagesHeader, to the pages inside the OtherPages folder of the app:

[!code-csharp]

Request the sample's Page1 page at localhost:5000/OtherPages/Page1 and inspect the headers to view the result:

Page app model convention

Use AddPageApplicationModelConvention to create and add an IPageApplicationModelConvention that invokes an action on the PageApplicationModel for the page with the speciifed name.

The sample demonstrates the use of AddPageApplicationModelConvention by adding a header, AboutHeader, to the About page:

[!code-csharp]

Request the sample's About page at localhost:5000/About and inspect the headers to view the result:

Configure a filter

ConfigureFilter configures the specified filter to apply. You can implement a filter class, but the sample app shows how to implement a filter in a lambda expression, which is implemented behind-the-scenes as a factory that returns a filter:

[!code-csharp]

The page app model is used to check the relative path for segments that lead to the Page2 page in the OtherPages folder. If the condition passes, a header is added. If not, the EmptyFilter is applied.

EmptyFilter is an Action filter. Since Action filters are ignored by Razor Pages, the EmptyFilter no-ops as intended if the path doesn't contain OtherPages/Page2.

Request the sample's Page2 page at localhost:5000/OtherPages/Page2 and inspect the headers to view the result:

Configure a filter factory

ConfigureFilter configures the specified factory to apply filters to all Razor Pages.

The sample app provides an example of using a filter factory by adding a header, FilterFactoryHeader, with two values to the app's pages:

[!code-csharp]

AddHeaderWithFactory.cs:

[!code-csharp]

Request the sample's About page at localhost:5000/About and inspect the headers to view the result:

Replace the default page app model provider

Razor Pages uses the IPageApplicationModelProvider interface to create a DefaultPageApplicationModelProvider. You can inherit from the default model provider to provide your own implementation logic for handler discovery and processing. The default implementation (reference source) establishes conventions for unnamed and named handler naming, which is described below.

Default unnamed handler methods

Handler methods for HTTP verbs ("unnamed" handler methods) follow a convention: On<HTTP verb>[Async] (appending Async is optional but recommended for async methods).

Unnamed handler method	Operation
OnGet/OnGetAsync	Initialize the page state.
OnPost/OnPostAsync	Handle POST requests.
OnDelete/OnDeleteAsync	Handle DELETE requests†.
OnPut/OnPutAsync	Handle PUT requests†.
OnPatch/OnPatchAsync	Handle PATCH requests†.

†Used for making API calls to the page.

Default named handler methods

Handler methods provided by the developer ("named" handler methods) follow a similar convention. The handler name appears after the HTTP verb or between the HTTP verb and Async: On<HTTP verb><handler name>[Async] (appending Async is optional but recommended for async methods). For example, methods that process messages might take the naming shown in the table below.

Example named handler method	Example operation
OnGetMessage/OnGetMessageAsync	Obtain a message.
OnPostMessage/OnPostMessageAsync	POST a message.
OnDeleteMessage/OnDeleteMessageAsync	DELETE a message†.
OnPutMessage/OnPutMessageAsync	PUT a message†.
OnPatchMessage/OnPatchMessageAsync	PATCH a message†.

†Used for making API calls to the page.

Customize handler method names

Assume that you prefer to change the way unnamed and named handler methods are named. An alternative naming scheme is to avoid starting the method names with "On" and use the first word segment to determine the HTTP verb. You can make other changes, such as converting the verbs for DELETE, PUT, and PATCH to POST. Such a scheme provides the method names shown in the following table.

Handler method	Operation
Get	Initialize the page state.
Post/PostAsync	Handle POST requests.
Delete/DeleteAsync	Handle DELETE requests†.
Put/PutAsync	Handle PUT requests†.
Patch/PatchAsync	Handle PATCH requests†.
GetMessage	Obtain a message.
PostMessage/PostMessageAsync	POST a message.
DeleteMessage/DeleteMessageAsync	POST a message to delete.
PutMessage/PutMessageAsync	POST a message to put.
PatchMessage/PatchMessageAsync	POST a message to patch.

†Used for making API calls to the page.

To establish this scheme, inherit from the DefaultPageApplicationModelProvider class and override the CreateHandlerModel method to supply custom logic for resolving PageModel handler names. The sample app shows you how this is done in its CustomPageApplicationModelProvider class:

[!code-csharp]

Highlights of the class include:

• The class inherits from DefaultPageApplicationModelProvider.
• The TryParseHandlerMethod processes a handler to determine the HTTP verb (httpMethod) and named handler name (handlerName) when creating the PageHandlerModel.
  • An Async postfix is ignored, if present.
  • Casing is used to parse the HTTP verb from the method name.
  • When the method name (without Async) is equal to the HTTP verb name, there's no named handler. The handlerName is set to null, and the method name is Get, Post, Delete, Put, or Patch.
  • When the method name (without Async) is longer than the HTTP verb name, there's a named handler. The handlerName is set to <method name (less 'Async', if present)>. For example, both "GetMessage" and "GetMessageAsync" yield a handler name of "GetMessage".
  • DELETE, PUT, and PATCH HTTP verbs are converted to POST.

Register the CustomPageApplicationModelProvider in the Startup class:

[!code-csharp]

The page model in Index.cshtml.cs shows how the ordinary handler method naming conventions are changed for pages in the app. The ordinary "On" prefix naming used with Razor Pages is removed. The method that initializes the page state is now named Get. You can see this convention used throughout the app if you open any page model for any of the pages.

Each of the other methods start with the HTTP verb that describes its processing. The two methods that start with Delete would normally be treated as DELETE HTTP verbs, but the logic in TryParseHandlerMethod explicitly sets the verb to POST for both handlers.

Note that Async is optional between DeleteAllMessages and DeleteMessageAsync. They're both asynchronous methods, but you can choose to use the Async postfix or not; we recommend that you do. DeleteAllMessages is used here for demonstration purposes, but we recommend that you name such a method DeleteAllMessagesAsync. It doesn't affect the processing of the sample's implementation, but using the Async postfix calls out the fact that it's an asynchronous method.

[!code-csharp]

Note the handler names provided in Index.cshtml match the DeleteAllMessages and DeleteMessageAsync handler methods:

[!code-cshtml]

Async in the handler method name DeleteMessageAsync is factored out by the TryParseHandlerMethod for handler matching of POST request to method. The asp-page-handler name of DeleteMessage is matched to the handler method DeleteMessageAsync.

MVC Filters and the Page filter (IPageFilter)

MVC Action filters are ignored by Razor Pages, since Razor Pages use handler methods. Other types of MVC filters are available for you to use: Authorization, Exception, Resource, and Result. For more information, see the Filters topic.

The Page filter (IPageFilter) is a filter that applies to Razor Pages. For more information, see Filter methods for Razor Pages.

Additional resources

• Razor Pages authorization conventions