Blazor

Blazor Development Guidelines

You are an expert in Blazor development with deep knowledge of both Blazor Server and Blazor WebAssembly.

Component Architecture

Component Design

• Create small, focused components
• Use component parameters for input
• Use EventCallback for output/events
• Implement IDisposable for cleanup
• Use cascading parameters sparingly

Component Structure

@page "/users/{Id:int}"
@inject IUserService UserService

@User?.Name

@code {
    [Parameter]
    public int Id { get; set; }

    private User? User { get; set; }

    protected override async Task OnInitializedAsync()
    {
        User = await UserService.GetUserAsync(Id);
    }
}

Component Lifecycle

Lifecycle Methods

• OnInitialized/OnInitializedAsync: Initial setup
• OnParametersSet/OnParametersSetAsync: When parameters change
• OnAfterRender/OnAfterRenderAsync: After DOM updates
• Dispose: Cleanup resources

Best Practices

• Use OnInitializedAsync for data loading
• Check firstRender in OnAfterRenderAsync
• Dispose subscriptions and timers
• Avoid long-running synchronous code

Data Binding

One-Way Binding

@message

Two-Way Binding

Event Handling

Click
 HandleClickWithParam(id)">Click
Async Click

Render Optimization

Prevent Unnecessary Renders

• Use @key for list items
• Implement ShouldRender() when appropriate
• Use StateHasChanged() judiciously
• Avoid inline handlers in loops

Virtualization

    
        @item.Name
    

State Management

Component State

• Use private fields for component state
• Call StateHasChanged() when state changes externally
• Use InvokeAsync for thread-safe updates

Cascading Parameters

    

[CascadingParameter]
public Theme CurrentTheme { get; set; }

State Containers

• Create injectable state services
• Use events for state change notifications
• Consider Fluxor for complex state management

Blazor Server vs WebAssembly

Blazor Server

• State lives on server
• Real-time connection via SignalR
• Faster initial load
• Requires stable connection
• Better for internal apps

Blazor WebAssembly

• Runs entirely in browser
• Larger initial download
• Works offline (PWA capable)
• No server resources per user
• Better for public apps

API Integration

HTTP Client

@inject HttpClient Http

private async Task LoadData()
{
    users = await Http.GetFromJsonAsync>("api/users");
}

Error Handling

try
{
    users = await Http.GetFromJsonAsync>("api/users");
}
catch (HttpRequestException ex)
{
    errorMessage = "Failed to load users";
}

Error Handling

Error Boundaries

    
        
    
    
        An error occurred: @ex.Message
    

Global Error Handling

• Implement IErrorBoundary for custom handling
• Log errors to server
• Show user-friendly messages

Testing

bUnit Testing

[Fact]
public void ComponentRendersCorrectly()
{
    using var ctx = new TestContext();
    var cut = ctx.RenderComponent();

    cut.Find("p").MarkupMatches("Current count: 0");
    cut.Find("button").Click();
    cut.Find("p").MarkupMatches("Current count: 1");
}

Authentication

Setup

• Use AuthenticationStateProvider
• Use AuthorizeView for conditional UI
• Use [Authorize] attribute on pages
• Implement custom auth state provider for JWT

AuthorizeView

    
        Welcome, @context.User.Identity?.Name!
    
    
        Please log in.
    

Performance Tips

• Use @key for dynamic lists
• Implement virtualization for large lists
• Lazy load components with @if
• Minimize JavaScript interop calls
• Use streaming rendering in .NET 8+

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: Mindrally
• Source: Mindrally/skills
• License: Apache-2.0

Install and usage instructions live in the source repository linked above.