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Migrate from ASP.NET Core in .NET 7 to .NET 8

This article explains how to update an existing ASP.NET Core in .NET 7 project to .NET 8.

Prerequisites

Update the .NET SDK version in global.json

If you rely on a global.json file to target a specific .NET SDK version, update the version property to the .NET 8 SDK version that's installed. For example:

{
  "sdk": {
-    "version": "7.0.100"
+    "version": "8.0.100"
  }
}

Update the target framework

Update the project file's Target Framework Moniker (TFM) to net8.0:

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
-    <TargetFramework>net7.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
  </PropertyGroup>

</Project>

Update package references

In the project file, update each Microsoft.AspNetCore.*, Microsoft.EntityFrameworkCore.*, Microsoft.Extensions.*, and System.Net.Http.Json package reference's Version attribute to 8.0.0 or later. For example:

<ItemGroup>
-   <PackageReference Include="Microsoft.AspNetCore.JsonPatch" Version="7.0.12" />
-   <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="7.0.12" />
-   <PackageReference Include="Microsoft.Extensions.Caching.Abstractions" Version="7.0.0" />
-   <PackageReference Include="System.Net.Http.Json" Version="7.0.1" />
+   <PackageReference Include="Microsoft.AspNetCore.JsonPatch" Version="8.0.0" />
+   <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="8.0.0" />
+   <PackageReference Include="Microsoft.Extensions.Caching.Abstractions" Version="8.0.0" />
+   <PackageReference Include="System.Net.Http.Json" Version="8.0.0" />
</ItemGroup>

Blazor

The following migration scenarios are covered:

For guidance on adding Blazor support to an ASP.NET Core app, see Integrate ASP.NET Core Razor components with MVC or Razor Pages.

Update a Blazor Server app

We recommend using Blazor Web Apps in .NET 8, but Blazor Server is supported. To continue using Blazor Server with .NET 8, follow the guidance in the first three sections of this article:

New Blazor features introduced for Blazor Web Apps aren't available to a Blazor Server app updated to run under .NET 8. If you wish to adopt the new .NET 8 Blazor features, follow the guidance in either of the following sections:

Adopt all Blazor Web App conventions

To optionally adopt all of the new Blazor Web App conventions, we recommend the following process:

  • Create a new app from the Blazor Web App project template. For more information, see Tooling for ASP.NET Core Blazor.
  • Move the your app's components and code to the new Blazor Web App, making modifications to adopt new features.
  • Update the layout and styles of the Blazor Web App.

New .NET 8 features are covered in What's new in ASP.NET Core in .NET 8. When updating an app from .NET 6 or earlier, see the migration and release notes (What's new articles) for intervening releases.

Convert a Blazor Server app into a Blazor Web App

Blazor Server apps are supported in .NET 8 without any code changes. Use the following guidance to convert a Blazor Server app into an equivalent .NET 8 Blazor Web App, which makes all of the new .NET 8 features available.

Important

This section focuses on the minimal changes required to convert a .NET 7 Blazor Server app into a .NET 8 Blazor Web App. To adopt all of the new Blazor Web App conventions, follow the guidance in the Adopt all Blazor Web App conventions section.

  1. Follow the guidance in the first three sections of this article:

  2. Move the contents of the App component (App.razor) to a new Routes component file (Routes.razor) added to the project's root folder. Leave the empty App.razor file in the app in the project's root folder.

  3. Add an entry to the _Imports.razor file to make shorthand render modes available to the app:

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

  4. Move the content in the _Host page (Pages/_Host.cshtml) to the empty App.razor file. Proceed to make the following changes to the App component.

    Note

    In the following example, the project's namespace is BlazorServerApp. Adjust the namespace to match your project.

    Remove the following lines from the top of the file:

    - @page "/"
- @using Microsoft.AspNetCore.Components.Web
- @namespace BlazorServerApp.Pages
- @addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers

    Replace the preceding lines with a line that injects an IHostEnvironment instance:

    @inject IHostEnvironment Env

    Remove the tilde (~) from the href of the <base> tag and replace with the base path for your app:

    - <base href="~/" />
+ <base href="/" />

    Remove the Component Tag Helper for the HeadOutlet component and replace it with the HeadOutlet component.

    Remove the following line:

    - <component type="typeof(HeadOutlet)" render-mode="ServerPrerendered" />

    Replace the preceding line with the following:

    <HeadOutlet @rendermode="InteractiveServer" />

    Remove the Component Tag Helper for the App component and replace it with the Routes component.

    Remove the following line:

    - <component type="typeof(App)" render-mode="ServerPrerendered" />

    Replace the preceding line with the following:

    <Routes @rendermode="InteractiveServer" />

    Note

    The preceding configuration assumes that the app's components adopt interactive server rendering. For more information, including how to adopt static server-side rendering (SSR), see ASP.NET Core Blazor render modes.

    Remove the Environment Tag Helpers for error UI and replace them with the following Razor markup.

    Remove the following lines:

    - <environment include="Staging,Production">
-     An error has occurred. This application may no longer respond until reloaded.
- </environment>
- <environment include="Development">
-     An unhandled exception has occurred. See browser dev tools for details.
- </environment>

    Replace the preceding lines with the following:

    @if (Env.IsDevelopment())
{
    <text>
        An unhandled exception has occurred. See browser dev tools for details.
    </text>
}
else
{
    <text>
        An error has occurred. This app may no longer respond until reloaded.
    </text>
}

    Change the Blazor script from blazor.server.js to blazor.web.js:

    - <script src="_framework/blazor.server.js"></script>
+ <script src="_framework/blazor.web.js"></script>

  5. Delete the Pages/_Host.cshtml file.

  6. Update Program.cs:

    Note

    In the following example, the project's namespace is BlazorServerApp. Adjust the namespace to match your project.

    Add a using statement to the top of the file for the project's namespace:

    using BlazorServerApp;

    Replace AddServerSideBlazor with AddRazorComponents and a chained call to AddInteractiveServerComponents.

    Remove the following line:

    - builder.Services.AddServerSideBlazor();

    Replace the preceding line with Razor component and interactive server component services. Calling AddRazorComponents adds antiforgery services (AddAntiforgery) by default.

    builder.Services.AddRazorComponents()
    .AddInteractiveServerComponents();

    Remove the following line:

    - app.MapBlazorHub();

    Replace the preceding line with a call to MapRazorComponents, supplying the App component as the root component type, and add a chained call to AddInteractiveServerRenderMode:

    app.MapRazorComponents<App>()
    .AddInteractiveServerRenderMode();

    Remove the following line:

    - app.MapFallbackToPage("/_Host");

    Remove Routing Middleware:

    - app.UseRouting();

    Add Antiforgery Middleware to the request processing pipeline after the line that adds HTTPS Redirection Middleware (app.UseHttpsRedirection):

    app.UseAntiforgery();

    The preceding call to app.UseAntiforgery must be placed after calls, if present, to app.UseAuthentication and app.UseAuthorization. There's no need to explicitly add antiforgery services (builder.Services.AddAntiforgery), as they're added automatically by AddRazorComponents, which was covered earlier.

  7. If the Blazor Server app was configured to disable prerendering, you can continue to disable prerendering for the updated app. In the App component, change the value assigned to the @rendermode Razor directive attributes for the HeadOutlet and Routes components.

    Change the value of the @rendermode directive attribute for both the HeadOutlet and Routes components to disable prerendering:

    - @rendermode="InteractiveServer"
+ @rendermode="new InteractiveServerRenderMode(prerender: false)"

    For more information, see ASP.NET Core Blazor render modes.

Update a Blazor WebAssembly app

Follow the guidance in the first three sections of this article:

For apps that adopt lazy assembly loading, change the file extension from .dll to .wasm in the app's implementation to reflect Blazor WebAssembly's adoption of Webcil assembly packaging.

Prior to the release of .NET 8, guidance in Deployment layout for ASP.NET Core hosted Blazor WebAssembly apps addresses environments that block clients from downloading and executing DLLs with a multipart bundling approach. In .NET 8 or later, Blazor uses the Webcil file format to address this problem. Multipart bundling using the experimental NuGet package described by the WebAssembly deployment layout article isn't supported for Blazor apps in .NET 8 or later. If you desire to continue using the multipart bundle package in .NET 8 or later apps, you can use the guidance in the article to create your own multipart bundling NuGet package, but it won't be supported by Microsoft.

Convert a hosted Blazor WebAssembly app into a Blazor Web App

Blazor WebAssembly apps are supported in .NET 8 without any code changes. Use the following guidance to convert an ASP.NET Core hosted Blazor WebAssembly app into an equivalent .NET 8 Blazor Web App, which makes all of the new .NET 8 features available.

Important

This section focuses on the minimal changes required to convert a .NET 7 ASP.NET Core hosted Blazor WebAssembly app into a .NET 8 Blazor Web App. To adopt all of the new Blazor Web App conventions, follow the guidance in the Adopt all Blazor Web App conventions section.

  1. Follow the guidance in the first three sections of this article:

    Important

    Using the preceding guidance, update the .Client, .Server, and .Shared projects of the solution.

  2. In the .Client project file (.csproj), add the following MSBuild properties:

    <NoDefaultLaunchSettingsFile>true</NoDefaultLaunchSettingsFile>
<StaticWebAssetProjectMode>Default</StaticWebAssetProjectMode>

    Also in the .Client project file, remove the Microsoft.AspNetCore.Components.WebAssembly.DevServer package reference:

    - <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly.DevServer"... />

  3. Move the file content from the .Client/wwwroot/index.html file to a new App component file (App.razor) created at the root of the .Server project. After you move the file's contents, delete the index.html file.

    Rename App.razor in the .Client project to Routes.razor.

    In Routes.razor, update the value of the AppAssembly attribute to typeof(Program).Assembly.

  4. In the .Client project, add an entry to the _Imports.razor file to make shorthand render modes available to the app:

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

    Make a copy of the .Client project's _Imports.razor file and add it to the .Server project.

  5. Make the following changes to the App.razor file:

    Replace the website's default website title (<title>...</title>) with a HeadOutlet component. Note the website title for use later and remove the title tags and title:

    - <title>...</title>

    Where you removed the title, place a HeadOutlet component assigning the Interactive WebAssembly render mode (prerendering disabled):

    <HeadOutlet @rendermode="new InteractiveWebAssemblyRenderMode(prerender: false)" />

    Change the CSS style bundle:

    - <link href="{CLIENT PROJECT ASSEMBLY NAME}.styles.css" rel="stylesheet">
+ <link href="{SERVER PROJECT ASSEMBLY NAME}.styles.css" rel="stylesheet">

    Placeholders in the preceding code:

    • {CLIENT PROJECT ASSEMBLY NAME}: Client project assembly name. Example: BlazorSample.Client
    • {SERVER PROJECT ASSEMBLY NAME}: Server project assembly name. Example: BlazorSample.Server

    Locate following <div>...</div> HTML markup:

    - <div id="app">
-     ...
- </div>

    Replace the preceding <div>...</div> HTML markup with the Routes component using the Interactive WebAssembly render mode (prerendering disabled):

    <Routes @rendermode="new InteractiveWebAssemblyRenderMode(prerender: false)" />

    Update the blazor.webassembly.js script to blazor.web.js:

    - <script src="_framework/blazor.webassembly.js"></script>
+ <script src="_framework/blazor.web.js"></script>

  6. Open the .Client project's layout file (.Client/Shared/MainLayout.razor) and add a PageTitle component with the website's default title ({TITLE} placeholder):

    <PageTitle>{TITLE}</PageTitle>

    Note

    Other layout files should also receive a PageTitle component with the default website title.

    For more information, see Control head content in ASP.NET Core Blazor apps.

  7. Remove the following lines from .Client/Program.cs:

    - builder.RootComponents.Add<App>("#app");
- builder.RootComponents.Add<HeadOutlet>("head::after");

  8. Update .Server/Program.cs:

    Add Razor component and interactive WebAssembly component services to the project. Call AddRazorComponents with a chained call to AddInteractiveWebAssemblyComponents. Calling AddRazorComponents adds antiforgery services (AddAntiforgery) by default.

    builder.Services.AddRazorComponents()
    .AddInteractiveWebAssemblyComponents();

    Add Antiforgery Middleware to the request processing pipeline.

    Place the following line after the call to app.UseHttpsRedirection. The call to app.UseAntiforgery must be placed after calls, if present, to app.UseAuthentication and app.UseAuthorization. There's no need to explicitly add antiforgery services (builder.Services.AddAntiforgery), as they're added automatically by AddRazorComponents, which was covered earlier.

    app.UseAntiforgery();

    Remove the following line:

    - app.UseBlazorFrameworkFiles();

    Remove the following line:

    - app.MapFallbackToFile("index.html");

    Replace the preceding line with a call to MapRazorComponents, supplying the App component as the root component type, and add chained calls to AddInteractiveWebAssemblyRenderMode and AddAdditionalAssemblies:

    app.MapRazorComponents<App>()
    .AddInteractiveWebAssemblyRenderMode()
    .AddAdditionalAssemblies(typeof({CLIENT APP NAMESPACE}._Imports).Assembly);

    In the preceding example, the {CLIENT APP NAMESPACE} placeholder is the namespace of the .Client project (for example, HostedBlazorApp.Client).

  9. Run the solution from the .Server project:

    For Visual Studio, confirm that the .Server project is selected in Solution Explorer when running the app.

    If using the .NET CLI, run the project from the .Server project's folder.

Update service and endpoint option configuration

With the release of Blazor Web Apps in .NET 8, Blazor service and endpoint option configuration is updated with the introduction of new API for interactive component services and component endpoint configuration.

Updated configuration guidance appears in the following locations:

Drop Blazor Server with Yarp routing workaround

If you previously followed the guidance in Enable ASP.NET Core Blazor Server support with Yarp in incremental migration for migrating a Blazor Server app with Yarp to .NET 6 or .NET 7, you can reverse the workaround steps that you took when following the article's guidance. Routing and deep linking for Blazor Server with Yarp work correctly in .NET 8.

Migrate CascadingValue components in layout components

Cascading parameters don't pass data across render mode boundaries, and layouts are statically rendered in otherwise interactive apps. Therefore, apps that seek to use cascading parameters in interactively rendered components won't be able to cascade the values from a layout.

The two approaches for migration are:

For more information, see Cascading values/parameters and render mode boundaries.

Migrate the BlazorEnableCompression MSBuild property

For Blazor WebAssembly apps that disable compression and target .NET 7 or earlier but are built with the .NET 8 SDK, the BlazorEnableCompression MSBuild property has changed to CompressionEnabled:

<PropertyGroup>
-   <BlazorEnableCompression>false</BlazorEnableCompression>
+   <CompressionEnabled>false</CompressionEnabled>
</PropertyGroup>

When using the .NET CLI publish command, use the new property:

dotnet publish -p:CompressionEnabled=false

For more information, see the following resources:

Migrate the <CascadingAuthenticationState> component to cascading authentication state services

In .NET 7 or earlier, the CascadingAuthenticationState component is wrapped around some part of the UI tree, for example around the Blazor router, to provide cascading authentication state:

<CascadingAuthenticationState>
    <Router ...>
        ...
    </Router>
</CascadingAuthenticationState>

In .NET 8, don't use the CascadingAuthenticationState component:

- <CascadingAuthenticationState>
      <Router ...>
          ...
      </Router>
- </CascadingAuthenticationState>

Instead, add cascading authentication state services to the service collection by calling AddCascadingAuthenticationState in the Program file:

builder.Services.AddCascadingAuthenticationState();

For more information, see the following resources:

New article on HTTP caching issues

We've added a new article that discusses some of the common HTTP caching issues that can occur when upgrading Blazor apps across major versions and how to address HTTP caching issues.

For more information, see Avoid HTTP caching issues when upgrading ASP.NET Core Blazor apps.

New article on class libraries with static server-side rendering (static SSR)

We've added a new article that discusses component library authorship in Razor class libraries (RCLs) with static server-side rendering (static SSR).

For more information, see ASP.NET Core Razor class libraries (RCLs) with static server-side rendering (static SSR).

Discover components from additional assemblies

When migrating from a Blazor Server app to a Blazor Web App, access the guidance in ASP.NET Core Blazor routing and navigation if the app uses routable components from additional assemblies, such as component class libraries.

Drop [Parameter] attribute when the parameter is supplied from a query string

The [Parameter] attribute is no longer required when supplying a parameter from the query string:

- [Parameter]
  [SupplyParameterFromQuery]

Blazor Server script fallback policy authorization

In .NET 7, the Blazor Server script (blazor.server.js) is served by Static File Middleware. Placing the call for Static File Middleware (UseStaticFiles) in the request processing pipeline before the call to Authorization Middleware (UseAuthorization) is sufficient in .NET 7 apps to serve the Blazor script to anonymous users.

In .NET 8, the Blazor Server script is served by its own endpoint, using endpoint routing. This change is introduced by Fixed bug - Passing options to UseStaticFiles breaks Blazor Server (dotnet/aspnetcore #45897).

Consider a multi-tenant scenario where:

  • Both the default and fallback policies are set identically.
  • The tenant is resolved using the first segment in the request path (for example, tld.com/tenant-name/...).
  • The requests to tenant endpoints are authenticated by an additional authentication scheme, which adds an additional identity to the request principal.
  • The fallback authorization policy has requirements that check claims via the additional identity.

Requests for the Blazor script file (blazor.server.js) are served at /_framework/blazor.server.js, which is hardcoded in the framework. Requests for the file aren't authenticated by the additional authentication scheme for tenants but are still challenged by the fallback policy, which results in returning an unauthorized result.

This problem is under evaluation for a new framework feature in MapRazorComponents broken with FallbackPolicy RequireAuthenticatedUser (dotnet/aspnetcore 51836), which is currently scheduled for .NET 9's release in November, 2024. Until then, you can work around this problem using any of the following three approaches:

  • Don't use a fallback policy. Apply the [Authorize] attribute in the _Imports.razor file to apply it to all of the components of the app. For non-blazor endpoints, explicitly use [Authorize] or RequireAuthorization.

  • Add [AllowAnonymous] to the /_framework/blazor.server.js endpoint in the Program file:

    app.MapBlazorHub().Add(endpointBuilder =>
{
    if (endpointBuilder is 
        RouteEndpointBuilder
        { 
            RoutePattern: { RawText: "/_framework/blazor.server.js" }
        })
    {
        endpointBuilder.Metadata.Add(new AllowAnonymousAttribute());
    }
});

  • Register a custom AuthorizationHandler that checks the HttpContext to allow the /_framework/blazor.server.js file through.

Docker

Update Docker images

For apps using Docker, update the Dockerfile FROM statements and scripts. Use a base image that includes the .NET 8 runtime. Consider the following docker pull command difference between ASP.NET Core in .NET 7 and .NET 8:

- docker pull mcr.microsoft.com/dotnet/aspnet:7.0
+ docker pull mcr.microsoft.com/dotnet/aspnet:8.0

Update Docker port

The default ASP.NET Core port configured in .NET container images has been updated from port 80 to 8080.

The new ASPNETCORE_HTTP_PORTS environment variable was added as a simpler alternative to ASPNETCORE_URLS.

For more information, see:

Breaking changes

Use the articles in Breaking changes in .NET to find breaking changes that might apply when upgrading an app to a newer version of .NET.