ASP.NET Core Blazor project structure

This article describes the files and folders that make up a Blazor app generated from a Blazor project template.

Blazor Server

Blazor Server project templates: blazorserver, blazorserver-empty

The Blazor Server templates create the initial files and directory structure for a Blazor Server app:

• If the blazorserver template is used, the app is populated with the following:
  • Demonstration code for a FetchData component that loads data from a weather forecast service (WeatherForecastService) and user interaction with a Counter component.
  • Bootstrap frontend toolkit.
• If the blazorserver-empty template is used, the app is created without demonstration code and Bootstrap.

Project structure:

• Data folder: Contains the WeatherForecast class and implementation of the WeatherForecastService that provides example weather data to the app's FetchData component.

• Pages folder: Contains the routable components/pages (.razor) that make up the Blazor app and the root Razor page of a Blazor Server app. The route for each page is specified using the @page directive. The template includes the following:

  • _Host.cshtml: The root page of the app implemented as a Razor Page:
    • When any page of the app is initially requested, this page is rendered and returned in the response.
    • The Host page specifies where the root App component (App.razor) is rendered.
  • Counter component (Counter.razor): Implements the Counter page.
  • Error component (Error.razor): Rendered when an unhandled exception occurs in the app.
  • FetchData component (FetchData.razor): Implements the Fetch data page.
  • Index component (Index.razor): Implements the Home page.

• Properties/launchSettings.json: Holds development environment configuration.

• Shared folder: Contains the following shared components and stylesheets:

  • MainLayout component (MainLayout.razor): The app's layout component.
  • MainLayout.razor.css: Stylesheet for the app's main layout.
  • NavMenu component (NavMenu.razor): Implements sidebar navigation. Includes the NavLink component (NavLink), which renders navigation links to other Razor components. The NavLink component automatically indicates a selected state when its component is loaded, which helps the user understand which component is currently displayed.
  • NavMenu.razor.css: Stylesheet for the app's navigation menu.
  • SurveyPrompt component (SurveyPrompt.razor): Blazor survey component.

• wwwroot: The Web Root folder for the app containing the app's public static assets.

• _Imports.razor: Includes common Razor directives to include in the app's components (.razor), such as @using directives for namespaces.

• App.razor: The root component of the app that sets up client-side routing using the Router component. The Router component intercepts browser navigation and renders the page that matches the requested address.

• appsettings.json and environmental app settings files: Provide configuration settings for the app.

• Program.cs: The app's entry point that sets up the ASP.NET Core host and contains the app's startup logic, including service registrations and request processing pipeline configuration:

  • Specifies the app's dependency injection (DI) services. Services are added by calling AddServerSideBlazor, and the WeatherForecastService is added to the service container for use by the example FetchData component.
  • Configures the app's request handling pipeline:
    • MapBlazorHub is called to set up an endpoint for the real-time connection with the browser. The connection is created with SignalR, which is a framework for adding real-time web functionality to apps.
    • MapFallbackToPage("/_Host") is called to set up the root page of the app (Pages/_Host.cshtml) and enable navigation.

Additional files and folders may appear in an app produced from a Blazor Server project template when additional options are configured. For example, generating an app with ASP.NET Core Identity includes additional assets for authentication and authorization features.

Blazor WebAssembly

Blazor WebAssembly project templates: blazorwasm, blazorwasm-empty

The Blazor WebAssembly templates create the initial files and directory structure for a Blazor WebAssembly app:

• If the blazorwasm template is used, the app is populated with the following:
  • Demonstration code for a FetchData component that loads data from a static asset (weather.json) and user interaction with a Counter component.
  • Bootstrap frontend toolkit.
• If the blazorwasm-empty template is used, the app is created without demonstration code and Bootstrap.

Project structure:

• Pages folder: Contains the routable components/pages (.razor) that make up the Blazor app. The route for each page is specified using the @page directive. The template includes the following components:

  • Counter component (Counter.razor): Implements the Counter page.
  • FetchData component (FetchData.razor): Implements the Fetch data page.
  • Index component (Index.razor): Implements the Home page.

• Properties/launchSettings.json: Holds development environment configuration.

• Shared folder: Contains the following shared components and stylesheets:

  • MainLayout component (MainLayout.razor): The app's layout component.
  • MainLayout.razor.css: Stylesheet for the app's main layout.
  • NavMenu component (NavMenu.razor): Implements sidebar navigation. Includes the NavLink component (NavLink), which renders navigation links to other Razor components. The NavLink component automatically indicates a selected state when its component is loaded, which helps the user understand which component is currently displayed.
  • NavMenu.razor.css: Stylesheet for the app's navigation menu.
  • SurveyPrompt component (SurveyPrompt.razor): Blazor survey component.

• wwwroot: The Web Root folder for the app containing the app's public static assets, including appsettings.json and environmental app settings files for configuration settings. The index.html webpage is the root page of the app implemented as an HTML page:

  • When any page of the app is initially requested, this page is rendered and returned in the response.
  • The page specifies where the root App component is rendered. The component is rendered at the location of the div DOM element with an id of app (<div id="app">Loading...</div>).

• _Imports.razor: Includes common Razor directives to include in the app's components (.razor), such as @using directives for namespaces.

• App.razor: The root component of the app that sets up client-side routing using the Router component. The Router component intercepts browser navigation and renders the page that matches the requested address.

• Program.cs: The app's entry point that sets up the WebAssembly host:

  • The App component is the root component of the app. The App component is specified as the div DOM element with an id of app (<div id="app">Loading...</div> in wwwroot/index.html) to the root component collection (builder.RootComponents.Add<App>("#app")).
  • Services are added and configured (for example, builder.Services.AddSingleton<IMyDependency, MyDependency>()).

Additional files and folders may appear in an app produced from a Blazor WebAssembly project template when additional options are configured. For example, generating an app with ASP.NET Core Identity includes additional assets for authentication and authorization features.

A hosted Blazor WebAssembly solution includes the following ASP.NET Core projects:

• "Client": The Blazor WebAssembly app.
• "Server": An app that serves the Blazor WebAssembly app and weather data to clients.
• "Shared": A project that maintains common classes, methods, and resources.

The solution is generated from the Blazor WebAssembly project template in Visual Studio with the ASP.NET Core Hosted checkbox selected or with the -ho|--hosted option using the .NET CLI's dotnet new blazorwasm command. For more information, see Tooling for ASP.NET Core Blazor.

The project structure of the client-side app in a hosted Blazor Webassembly solution ("Client" project) is the same as the project structure for a standalone Blazor WebAssembly app. Additional files in a hosted Blazor WebAssembly solution:

• The "Server" project includes a weather forecast controller at Controllers/WeatherForecastController.cs that returns weather data to the "Client" project's FetchData component.
• The "Shared" project includes a weather forecast class at WeatherForecast.cs that represents weather data for the "Client" and "Server" projects.

Location of <head> content

In Blazor Server apps, <head> content is located in the Pages/_Host.cshtml file.

In Blazor WebAssembly apps, <head> content is located in the wwwroot/index.html file.

Dual Blazor Server/Blazor WebAssembly app

To create an app that can run as either a Blazor Server app or a Blazor WebAssembly app, one approach is to place all of the app logic and components into a Razor class library (RCL) and reference the RCL from separate Blazor Server and Blazor WebAssembly projects. For common services whose implementations differ based on the hosting model, define the service interfaces in the RCL and implement the services in the Blazor Server and Blazor WebAssembly projects.

Additional resources

• Tooling for ASP.NET Core Blazor
• ASP.NET Core Blazor hosting models
• Minimal APIs quick reference
• Blazor samples GitHub repository (dotnet/blazor-samples)