.NET 10 Vertical Slice Architecture

Organize code by feature, not by layer. Each feature is self-contained with its endpoint, request/response, validation, and handler in a single file.

Project Structure

src/ ├── Features/ │ ├── Products/ │ │ ├── GetProduct.cs │ │ ├── CreateProduct.cs │ │ └── ProductMapper.cs │ └── Orders/ │ └── ... ├── Shared/ │ ├── Results/ │ │ ├── Result.cs │ │ └── Error.cs │ └── Validation/ │ └── ValidationResult.cs ├── Entities/ └── Program.cs

Feature Slice Pattern

One file per operation containing everything needed:

// Features/Products/CreateProduct.cs public static class CreateProduct { public sealed record Request(string Name, decimal Price); public sealed record Response(int Id, string Name, decimal Price);

public static async Task<Result<Response>> HandleAsync(
    Request request, AppDbContext db, CancellationToken ct)
{
    var validation = Validate(request);
    if (!validation.IsValid)
        return validation.ToResult<Response>(null!);

    var product = new Product { Name = request.Name, Price = request.Price };
    db.Products.Add(product);
    await db.SaveChangesAsync(ct);

    return new Response(product.Id, product.Name, product.Price);
}

private static ValidationResult Validate(Request request) =>
    ValidationExtensions.Validate()
        .NotEmpty(request.Name, "Name")
        .GreaterThan(request.Price, 0, "Price");

public static void MapEndpoint(IEndpointRouteBuilder app) => app
    .MapPost("/api/products", async (Request request, AppDbContext db, CancellationToken ct) =>
        (await HandleAsync(request, db, ct)).ToCreatedResponse(r => $"/api/products/{r.Id}"))
    .WithName("CreateProduct")
    .WithTags("Products");

}

Core Principles

• Result pattern only - Never throw exceptions, return Result<T> or Result

• Static handlers - Use public static async Task<Result<T>> HandleAsync(...)

• Inline validation - Validate at handler start, return early on failure

• Manual mapping - Use extension methods in *Mapper.cs files

• Projections - Use .Select() for queries, avoid loading full entities

References

See detailed implementations in the references/ folder:

• Result Pattern - Error types, Result class, HTTP mapping

• Validation - ValidationResult, fluent extensions

• Feature Examples - CRUD, filtering, pagination

Guidelines

• One feature = one file (endpoint + request/response + validation + handler)

• Name files by operation: CreateProduct.cs , GetProducts.cs

• Keep entities in shared folder (only cross-cutting concern)

• Use [AsParameters] for query parameters

• Group endpoints with .WithTags() for OpenAPI