AspNetCore.Docs/aspnetcore/razor-components/routing.md

title	author	description	monikerRange	ms.author	ms.custom	ms.date	uid
Razor Components routing	guardrex	Learn how to route requests in apps and about the NavLink component.	>= aspnetcore-3.0	riande	mvc	02/01/2019	razor-components/routing

Razor Components routing

By Luke Latham

Learn how to route requests in apps and about the NavLink component.

View or download sample code (how to download). See the Get started topic for prerequisites.

Route templates

The <Router> component enables routing, and a route template is provided to each accessible component. The <Router> component appears in the App.cshtml file:

<Router AppAssembly=typeof(Program).Assembly />

When a *.cshtml file with an @page directive is compiled, the generated class is given a RouteAttribute specifying the route template. At runtime, the router looks for component classes with a RouteAttribute and renders whichever component has a route template that matches the requested URL.

Multiple route templates can be applied to a component. In the sample app, the following component responds to requests for /BlazorRoute and /DifferentBlazorRoute.

Pages/BlazorRoute.cshtml:

[!code-cshtml]

<Router> supports setting a fallback component for rendering when a requested route isn't resolved. Enable this opt-in scenario by setting the FallbackComponent parameter to the type of the fallback component class.

The following example sets a component defined in Pages/MyFallbackRazorComponent.cshtml as the fallback component for a <Router>:

<Router ... FallbackComponent="typeof(Pages.MyFallbackRazorComponent)" />

[!IMPORTANT] To generate routes properly, the app must include a <base> tag in its wwwroot/index.html file with the app base path specified in the href attribute (<base href="/" />). For more information, see Host and deploy: App base path.

Route parameters

The router uses route parameters to populate the corresponding component parameters with the same name (case insensitive).

Pages/RouteParameter.cshtml:

[!code-cshtml]

Optional parameters aren't supported yet, so two @page directives are applied in the example above. The first permits navigation to the component without a parameter. The second @page directive takes the {text} route parameter and assigns the value to the Text property.

Route constraints

A route constraint enforces type matching on a route segment to a component.

In the following example, the route to the Users component only matches if:

• An Id route segment is present on the request URL.
• The Id segment is an integer (int).

@page "/Users/{Id:int}"

<h1>The user Id is @Id!</h1>

@functions {
    [Parameter]
    private int Id { get; set; }
}

The route constraints shown in the following table are available for use. For the route constraints that match with the invariant culture, see the warning below the table for more information.

Constraint	Example	Example Matches	Invariant culture matching
bool	{active:bool}	true, FALSE	No
datetime	{dob:datetime}	2016-12-31, 2016-12-31 7:32pm	Yes
decimal	{price:decimal}	49.99, -1,000.01	Yes
double	{weight:double}	1.234, -1,001.01e8	Yes
float	{weight:float}	1.234, -1,001.01e8	Yes
guid	{id:guid}	CD2C1638-1638-72D5-1638-DEADBEEF1638, {CD2C1638-1638-72D5-1638-DEADBEEF1638}	No
int	{id:int}	123456789, -123456789	Yes
long	{ticks:long}	123456789, -123456789	Yes

[!WARNING] Route constraints that verify the URL and are converted to a CLR type (such as int or DateTime) always use the invariant culture. These constraints assume that the URL is non-localizable.

NavLink component

Use a NavLink component in place of HTML <a> elements when creating navigation links. A NavLink component behaves like an <a> element, except it toggles an active CSS class based on whether its href matches the current URL. The active class helps a user understand which page is the active page among the navigation links displayed.

The NavMenu component in the sample app creates a Bootstrap nav bar that demonstrates how to use NavLink components. The following markup shows the first two NavLinks in the Shared/NavMenu.cshtml file.

[!code-cshtml]

There are two NavLinkMatch options:

• NavLinkMatch.All – Specifies that the NavLink should be active when it matches the entire current URL.
• NavLinkMatch.Prefix – Specifies that the NavLink should be active when it matches any prefix of the current URL.

In the preceding example, the Home NavLink (href="") matches all URLs and always receives the active CSS class. The second NavLink only receives the active class when the user visits the BlazorRoute component (href="BlazorRoute").