blazor.md

title	author	description	monikerRange	ms.author	ms.custom	ms.date	uid
Enable ASP.NET Core Blazor Server support with Yarp in incremental migration	twsouthwick	Learn how to enable ASP.NET Core Blazor Server support with Yarp in incremental migration.	>= aspnetcore-6.0 < aspnetcore-8.0	tasou	mvc	03/01/2023	migration/inc/blazor

Enable ASP.NET Core Blazor Server support with Yarp in incremental migration

When adding Yarp to a Blazor Server app, both attempt to act as fallback routes for the app's request routing. Either Blazor or Yarp handles routing arbitrarily, which means that scenarios such as deep linking in Blazor may fail. This will be fixed in the .NET 8 release later this year. For migration to ASP.NET Core 6.0 and 7.0, map Blazor's endpoints to achieve correct request routing by following the guidance in this article.

Add the following route builder extensions class to the project.

BlazorEndpointRouteBuilderExtensions.cs:

[!code-csharp]

In the preceding code:

• xref:Microsoft.AspNetCore.Builder.EndpointBuilder.DisplayName?displayProperty=nameWithType defaults to Fallback {route}. The line that changes it to Blazor {route} (b.DisplayName = $"Blazor {route}";) identifies the Blazor route as explicitly registered.
• For the line that sets the route order (((RouteEndpointBuilder)b).Order = -1;), {page} has a route order of 0 by default. Setting the Blazor route order to -1 ensures the order is changed to give the Blazor route precedence.

Update the app registration for using Blazor in Program.cs:

- app.MapFallbackToPage("/_Host");
+ app.MapBlazorPages("/_Host");

At this point, the app should route requests correctly for Blazor and Yarp, including deep linking to pages.