From dotnet-skills
Building Blazor apps. Hosting models, render modes, routing, streaming rendering, prerender.
npx claudepluginhub wshaddix/dotnet-skillsThis skill uses the workspace's default tool permissions.
Searches, retrieves, and installs Agent Skills from prompts.chat registry using MCP tools like search_skills and get_skill. Activates for finding skills, browsing catalogs, or extending Claude.
Searches prompts.chat for AI prompt templates by keyword or category, retrieves by ID with variable handling, and improves prompts via AI. Use for discovering or enhancing prompts.
Compares coding agents like Claude Code and Aider on custom YAML-defined codebase tasks using git worktrees, measuring pass rate, cost, time, and consistency.
Blazor hosting models, render modes, project setup, routing, enhanced navigation, streaming rendering, and AOT-safe patterns. Covers all five hosting models (InteractiveServer, InteractiveWebAssembly, InteractiveAuto, Static SSR, Hybrid) with trade-off analysis for each.
Scope boundary: This skill owns Blazor project setup, hosting model selection, render mode configuration, routing, enhanced navigation, streaming rendering, and AOT-safe patterns. Component architecture (lifecycle, state management, JS interop, EditForm) is owned by [skill:dotnet-blazor-components]. Authentication across hosting models is owned by [skill:dotnet-blazor-auth].
Out of scope: bUnit component testing -- see [skill:dotnet-blazor-testing]. Standalone SignalR patterns -- see [skill:dotnet-realtime-communication]. Browser-based E2E testing -- see [skill:dotnet-playwright]. UI framework selection decision tree -- see [skill:dotnet-ui-chooser].
Cross-references: [skill:dotnet-blazor-components] for component architecture, [skill:dotnet-blazor-auth] for authentication, [skill:dotnet-blazor-testing] for bUnit testing, [skill:dotnet-realtime-communication] for standalone SignalR, [skill:dotnet-playwright] for E2E testing, [skill:dotnet-ui-chooser] for framework selection, [skill:dotnet-accessibility] for accessibility patterns (ARIA, keyboard nav, screen readers).
Blazor Web App (.NET 8+) is the default project template, replacing the separate Blazor Server and Blazor WebAssembly templates. Render modes can be set globally, per-page, or per-component.
| Render Mode | Attribute | Interactivity | Connection | Best For |
|---|---|---|---|---|
| Static SSR | (none / default) | None -- server renders HTML, no interactivity | HTTP request only | Content pages, SEO, forms with minimal interactivity |
| InteractiveServer | @rendermode InteractiveServer | Full | SignalR circuit | Low-latency interactivity, full server access, small user base |
| InteractiveWebAssembly | @rendermode InteractiveWebAssembly | Full (after download) | None (runs in browser) | Offline-capable, large user base, reduced server load |
| InteractiveAuto | @rendermode InteractiveAuto | Full | SignalR initially, then WASM | Best of both -- immediate interactivity, eventual client-side |
| Blazor Hybrid | BlazorWebView in MAUI/WPF/WinForms | Full (native) | None (runs in-process) | Desktop/mobile apps with web UI, native API access |
| Concern | Static SSR | InteractiveServer | InteractiveWebAssembly | InteractiveAuto | Hybrid |
|---|---|---|---|---|---|
| First load | Fast | Fast | Slow (WASM download) | Fast (Server first) | Instant (local) |
| Server resources | Minimal | Per-user circuit | None after download | Circuit then none | None |
| Offline support | No | No | Yes | Partial | Yes |
| Full .NET API access | Yes (server) | Yes (server) | Limited (browser sandbox) | Varies by phase | Yes (native) |
| Scalability | High | Limited by circuits | High | High (after WASM) | N/A (local) |
| SEO | Yes | Prerender | Prerender | Prerender | N/A |
Global (App.razor):
<!-- Sets default render mode for all pages -->
<Routes @rendermode="InteractiveServer" />
Per-page:
@page "/dashboard"
@rendermode InteractiveServer
<h1>Dashboard</h1>
Per-component:
<Counter @rendermode="InteractiveWebAssembly" />
Gotcha: Without an explicit render mode boundary, a child component cannot request a more interactive render mode than its parent. However, interactive islands are supported: you can place an @rendermode attribute on a component embedded in a Static SSR page to create a render mode boundary, enabling interactive children under otherwise static content.
# Creates a Blazor Web App with InteractiveServer render mode
dotnet new blazor -n MyApp
# With specific interactivity options
dotnet new blazor -n MyApp --interactivity Auto # InteractiveAuto
dotnet new blazor -n MyApp --interactivity WebAssembly # InteractiveWebAssembly
dotnet new blazor -n MyApp --interactivity Server # InteractiveServer (default)
dotnet new blazor -n MyApp --interactivity None # Static SSR only
MyApp/
MyApp/ # Server project
Program.cs # Host builder, services, middleware
Components/
App.razor # Root component (sets global render mode)
Routes.razor # Router component
Layout/
MainLayout.razor # Main layout
Pages/
Home.razor # Static SSR by default
Counter.razor # Can set per-page render mode
MyApp.Client/ # Client project (only if WASM or Auto)
Pages/
Counter.razor # Components that run in browser
Program.cs # WASM entry point
When using InteractiveAuto or InteractiveWebAssembly, components that must run in the browser go in the .Client project. Components in the server project run on the server only.
<!-- .csproj for MAUI Blazor Hybrid -->
<Project Sdk="Microsoft.NET.Sdk.Razor">
<PropertyGroup>
<TargetFrameworks>net10.0-android;net10.0-ios;net10.0-maccatalyst</TargetFrameworks>
<OutputType>Exe</OutputType>
<UseMaui>true</UseMaui>
</PropertyGroup>
</Project>
// MainPage.xaml.cs hosts BlazorWebView
public partial class MainPage : ContentPage
{
public MainPage()
{
InitializeComponent();
}
}
<!-- MainPage.xaml -->
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
xmlns:b="clr-namespace:Microsoft.AspNetCore.Components.WebView.Maui;assembly=Microsoft.AspNetCore.Components.WebView.Maui">
<b:BlazorWebView HostPage="wwwroot/index.html">
<b:BlazorWebView.RootComponents>
<b:RootComponent Selector="#app" ComponentType="{x:Type local:Routes}" />
</b:BlazorWebView.RootComponents>
</b:BlazorWebView>
</ContentPage>
@page "/products"
@page "/products/{Category}"
<h1>Products</h1>
@if (!string.IsNullOrEmpty(Category))
{
<p>Category: @Category</p>
}
@code {
[Parameter]
public string? Category { get; set; }
}
@page "/products/{Id:int}"
@page "/orders/{Date:datetime}"
@page "/search/{Query:minlength(3)}"
@code {
[Parameter] public int Id { get; set; }
[Parameter] public DateTime Date { get; set; }
[Parameter] public string Query { get; set; } = "";
}
@page "/search"
@code {
[SupplyParameterFromQuery]
public string? Term { get; set; }
[SupplyParameterFromQuery(Name = "page")]
public int CurrentPage { get; set; } = 1;
}
@inject NavigationManager Navigation
// Programmatic navigation
Navigation.NavigateTo("/products/electronics");
// With query string
Navigation.NavigateTo("/search?term=keyboard&page=2");
// Force full page reload (bypasses enhanced navigation)
Navigation.NavigateTo("/external-page", forceLoad: true);
Enhanced navigation intercepts link clicks and form submissions to update only the changed DOM content, preserving page state and avoiding full page reloads. This applies to Static SSR and prerendered pages.
<!-- Disable enhanced navigation for a specific link -->
<a href="/legacy-page" data-enhance-nav="false">Legacy Page</a>
<!-- Disable enhanced form handling for a specific form -->
<form method="post" data-enhance="false">
...
</form>
Gotcha: Enhanced navigation may interfere with third-party JavaScript libraries that expect full page loads. Use data-enhance-nav="false" on links that navigate to pages with JS that initializes on DOMContentLoaded.
Streaming rendering sends initial HTML immediately (with placeholder content), then streams updates as async operations complete. Useful for pages with slow data sources.
@page "/dashboard"
@attribute [StreamRendering]
<h1>Dashboard</h1>
@if (orders is null)
{
<p>Loading orders...</p>
}
else
{
<table>
@foreach (var order in orders)
{
<tr><td>@order.Id</td><td>@order.Total</td></tr>
}
</table>
}
@code {
private List<OrderDto>? orders;
protected override async Task OnInitializedAsync()
{
// Initial HTML sent immediately with "Loading orders..."
// Updated HTML streamed when this completes
orders = await OrderService.GetRecentOrdersAsync();
}
}
Behavior per render mode:
[StreamRendering] attribute primarily benefits the prerender phase.When targeting Blazor WebAssembly with Native AOT (ahead-of-time compilation) or IL trimming, avoid patterns that rely on runtime reflection.
// CORRECT: Source-generated JSON serialization (AOT-compatible)
[JsonSerializable(typeof(ProductDto))]
[JsonSerializable(typeof(List<ProductDto>))]
[JsonSourceGenerationOptions(PropertyNamingPolicy = JsonKnownNamingPolicy.CamelCase)]
public partial class AppJsonContext : JsonSerializerContext { }
// Register in Program.cs
builder.Services.ConfigureHttpJsonOptions(options =>
{
options.SerializerOptions.TypeInfoResolverChain.Insert(0, AppJsonContext.Default);
});
// Usage in HttpClient calls
var products = await Http.GetFromJsonAsync<List<ProductDto>>(
"/api/products",
AppJsonContext.Default.ListProductDto);
// WRONG: Reflection-based serialization (fails under AOT/trimming)
var products = await Http.GetFromJsonAsync<List<ProductDto>>("/api/products");
// CORRECT: Use IJSRuntime with explicit method names (no dynamic dispatch)
await JSRuntime.InvokeVoidAsync("localStorage.setItem", "key", "value");
var value = await JSRuntime.InvokeAsync<string>("localStorage.getItem", "key");
// CORRECT: Use IJSObjectReference for module imports (.NET 8+)
var module = await JSRuntime.InvokeAsync<IJSObjectReference>(
"import", "./js/chart.js");
await module.InvokeVoidAsync("initChart", elementRef, data);
await module.DisposeAsync();
// WRONG: Dynamic dispatch via reflection (trimmed away)
// var method = typeof(JSRuntime).GetMethod("InvokeAsync");
// method.MakeGenericMethod(returnType).Invoke(...)
<!-- Preserve types used dynamically in components -->
<ItemGroup>
<TrimmerRootAssembly Include="MyApp.Client" />
</ItemGroup>
For types that must be preserved from trimming:
// Mark types that are accessed via reflection
[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.All)]
public class DynamicFormModel
{
// Properties discovered at runtime for form generation
public string Name { get; set; } = "";
public int Age { get; set; }
}
Activator.CreateInstance or Type.GetType to resolve services. Use the built-in DI container with explicit registrations.Assembly.Load or Assembly.GetTypes() at runtime. Register all types at startup.System.Reflection.Emit or System.Linq.Expressions.Expression.Compile(). Use source generators instead.JsonSerializer.Deserialize<T>(json) without a JsonSerializerContext. Always provide a source-generated context.Prerendering generates HTML on the server before the interactive runtime loads. This improves perceived performance and SEO.
<!-- Component prerenders on server, then becomes interactive -->
<Counter @rendermode="InteractiveServer" />
By default, interactive components prerender. To disable:
@rendermode @(new InteractiveServerRenderMode(prerender: false))
State computed during prerendering is lost when the component reinitializes interactively. Use PersistentComponentState to preserve it:
@inject PersistentComponentState ApplicationState
@implements IDisposable
@code {
private List<ProductDto>? products;
private PersistingComponentStateSubscription _subscription;
protected override async Task OnInitializedAsync()
{
_subscription = ApplicationState.RegisterOnPersisting(PersistState);
if (!ApplicationState.TryTakeFromJson<List<ProductDto>>(
"products", out var restored))
{
products = await ProductService.GetProductsAsync();
}
else
{
products = restored;
}
}
private Task PersistState()
{
ApplicationState.PersistAsJson("products", products);
return Task.CompletedTask;
}
public void Dispose() => _subscription.Dispose();
}
These features are available when net10.0 TFM is detected. They are stable and require no preview opt-in.
.NET 10 adds blazor.web.js preloading of WebAssembly assemblies during the Server phase of InteractiveAuto. When the user first loads a page, the WASM runtime and app assemblies download in the background while the Server circuit handles interactivity. Subsequent navigations switch to WASM faster because assemblies are already cached.
<!-- No code changes needed -- preloading is automatic in .NET 10 -->
<!-- Verify in browser DevTools Network tab: assemblies download during Server phase -->
.NET 10 extends EditForm validation with improved error message formatting and support for IValidatableObject in Static SSR forms. Validation messages render correctly with enhanced form handling (Enhance attribute) without requiring a full page reload.
// IValidatableObject works in Static SSR enhanced forms in .NET 10
public sealed class OrderModel : IValidatableObject
{
[Required]
public string ProductId { get; set; } = "";
[Range(1, 100)]
public int Quantity { get; set; }
public IEnumerable<ValidationResult> Validate(ValidationContext context)
{
if (ProductId == "DISCONTINUED" && Quantity > 0)
{
yield return new ValidationResult(
"Cannot order discontinued products",
[nameof(ProductId), nameof(Quantity)]);
}
}
}
.NET 10 adds MapBlazorDiagnostics middleware for inspecting Blazor circuit and component state in development:
// Program.cs -- available in .NET 10
if (app.Environment.IsDevelopment())
{
app.MapBlazorDiagnostics(); // Exposes /_blazor/diagnostics endpoint
}
The diagnostics endpoint shows active circuits, component tree, render mode assignments, and timing data. Use it to debug render mode boundaries and component lifecycle issues during development.
.Client project.PersistentComponentState when prerendering. Without it, data fetched during prerender is discarded and re-fetched when the component becomes interactive, causing a visible flicker.JsonSerializerContext with source-generated serializers for AOT compatibility and trimming safety.NavigateTo("/page", forceLoad: true) bypasses enhanced navigation and causes a full page reload.dotnet workload install maui)