---

name: "moai-lang-csharp" description: "C# 12 / .NET 8 development specialist covering ASP.NET Core, Entity Framework, Blazor, and modern C# patterns. Use when developing .NET APIs, web applications, or enterprise solutions." version: 2.0.0 category: "language" modularized: true allowed-tools: "Read, Grep, Glob, mcp__context7__resolve-library-id, mcp__context7__get-library-docs" context7-libraries: ['/dotnet/aspnetcore', '/dotnet/efcore', '/dotnet/runtime'] updated: 2026-01-06 status: "active"

C# 12 / .NET 8 Development Specialist

Modern C# development with ASP.NET Core, Entity Framework Core, Blazor, and enterprise patterns.

Quick Reference

Auto-Triggers: .cs, .csproj, .sln files, C# projects, .NET solutions, ASP.NET Core applications

Core Stack:

• C# 12: Primary constructors, collection expressions, alias any type, default lambda parameters
• .NET 8: Minimal APIs, Native AOT, improved performance, WebSockets
• ASP.NET Core 8: Controllers, Endpoints, Middleware, Authentication
• Entity Framework Core 8: DbContext, migrations, LINQ, query optimization
• Blazor: Server/WASM components, InteractiveServer, InteractiveWebAssembly
• Testing: xUnit, NUnit, FluentAssertions, Moq

Quick Commands:

# Create .NET 8 Web API project
dotnet new webapi -n MyApi --framework net8.0

# Create Blazor Web App
dotnet new blazor -n MyBlazor --interactivity Auto

# Add Entity Framework Core
dotnet add package Microsoft.EntityFrameworkCore.SqlServer
dotnet add package Microsoft.EntityFrameworkCore.Design

# Add FluentValidation and MediatR
dotnet add package FluentValidation.AspNetCore
dotnet add package MediatR

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Module Index

This skill uses progressive disclosure with specialized modules for deep coverage:

Language Features

• C# 12 Features - Primary constructors, collection expressions, type aliases, default lambdas

Web Development

• ASP.NET Core 8 - Minimal API, Controllers, Middleware, Authentication
• Blazor Components - Server, WASM, InteractiveServer, Components

Data Access

• Entity Framework Core 8 - DbContext, Repository pattern, Migrations, Query optimization

Architecture Patterns

• CQRS and Validation - MediatR CQRS, FluentValidation, Handler patterns

Reference Materials

• API Reference - Complete API reference, Context7 library mappings
• Code Examples - Production-ready examples, testing templates

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Implementation Quick Start

Project Structure (Clean Architecture)

src/
├── MyApp.Api/              # ASP.NET Core Web API
│   ├── Controllers/        # API Controllers
│   ├── Endpoints/          # Minimal API endpoints
│   └── Program.cs          # Application entry
├── MyApp.Application/      # Business logic layer
│   ├── Commands/           # CQRS Commands
│   ├── Queries/            # CQRS Queries
│   └── Validators/         # FluentValidation
├── MyApp.Domain/           # Domain entities
│   ├── Entities/           # Domain models
│   └── Interfaces/         # Repository interfaces
└── MyApp.Infrastructure/   # Data access layer
    ├── Data/               # DbContext
    └── Repositories/       # Repository implementations

Essential Patterns

Primary Constructor with DI:

public class UserService(IUserRepository repository, ILogger<UserService> logger)
{
    public async Task<User?> GetByIdAsync(Guid id)
    {
        logger.LogInformation("Fetching user {UserId}", id);
        return await repository.FindByIdAsync(id);
    }
}

Minimal API Endpoint:

app.MapGet("/api/users/{id:guid}", async (Guid id, IUserService service) =>
{
    var user = await service.GetByIdAsync(id);
    return user is not null ? Results.Ok(user) : Results.NotFound();
})
.WithName("GetUser")
.WithOpenApi();

Entity Configuration:

public class UserConfiguration : IEntityTypeConfiguration<User>
{
    public void Configure(EntityTypeBuilder<User> builder)
    {
        builder.HasKey(u => u.Id);
        builder.Property(u => u.Email).HasMaxLength(256).IsRequired();
        builder.HasIndex(u => u.Email).IsUnique();
    }
}

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Context7 Integration

For latest documentation, use Context7 MCP tools:

# ASP.NET Core documentation
mcp__context7__resolve-library-id("aspnetcore")
mcp__context7__get-library-docs("/dotnet/aspnetcore", "minimal-apis middleware")

# Entity Framework Core documentation
mcp__context7__resolve-library-id("efcore")
mcp__context7__get-library-docs("/dotnet/efcore", "dbcontext migrations")

# .NET Runtime documentation
mcp__context7__resolve-library-id("dotnet runtime")
mcp__context7__get-library-docs("/dotnet/runtime", "collections threading")

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Quick Troubleshooting

Build and Runtime:

dotnet build --verbosity detailed    # Detailed build output
dotnet run --launch-profile https    # Run with HTTPS profile
dotnet ef database update            # Apply EF migrations
dotnet ef migrations add Initial     # Create new migration

Common Patterns:

// Null reference handling
var user = await context.Users.FindAsync(id);
ArgumentNullException.ThrowIfNull(user, nameof(user));

// Async enumerable for streaming
public async IAsyncEnumerable<User> StreamUsersAsync(
    [EnumeratorCancellation] CancellationToken ct = default)
{
    await foreach (var user in context.Users.AsAsyncEnumerable().WithCancellation(ct))
    {
        yield return user;
    }
}

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Works Well With

• moai-domain-backend - API design, database integration patterns
• moai-platform-deploy - Azure, Docker, Kubernetes deployment
• moai-workflow-testing - Testing strategies and patterns
• moai-foundation-quality - Code quality standards
• moai-essentials-debug - Debugging .NET applications