Simple Clean/Vertical Slice Template for .Net 9 Webapi

└───src
    ├───Api
    │   ├───Endpoints
    │   │   └───Quotes
    │   ├───Extensions
    │   ├───Logs
    │   ├───Middleware
    │   └───Properties
 ├───Application
    │   ├───Abstractions
    │   │   ├───Behaviors
    │   │   ├───External
    │   │   └───Messaging
    │   ├───Features
    │   │   └───Quotes
    ├───Domain
    │   └───Quotes
    ├───Infrastructure
    │   ├───Database
    │   ├───External (e.g., HttpClients)
    │   ├───Migrations
    └───SharedCore

Proper syntax for creating a new migration:

From Root of the solution

dotnet ef migrations add Init \
  --project src/Infrastructure \
  --startup-project src/Api

Apply DB Update (From solution root)

dotnet ef database update --project src/Infrastructure/ --startup-project src/Api/

Condensed Feature Command/Query Files

• Delete

  • public sealed record DeleteXXXCommand(id/guid) : IRequest<Resultoptional:TResult>

  • public sealed class DeleteXXXHandler(context) : IRequestHandler<DeleteXXXCommand, Resultoptional:TResult

    • Handle()
      • return Result.Success(), Result.Failure()

  • public class DeleteXXXValidator : AbstractValidator

    • public DeleteXXXValidator() { Rules }

  • internal sealed class DeleteXXXEndpoint : IEndpoint

    • MapEndpoint()
      • app.MapDelete(...) (ISender handler, int/guid id, cancellationtoken ct)
        • var result = await Handler.Send(new DeleteXXXCommand(id), ct)
        • return result.Match(Results.NoContent{-other options exist-}, CustomResults.Problem)

• Create

  • public sealed record CreateXXXCommand(details) : IRequest<Result<id/guid>>
  • public sealed class CreateXXXCommand(context) : IRequestHandler<CreateXXXCommand, Result<int/guid>>
    • Handle()
      • return Result.Success(), Result.Failure
  • public sealed class CreateXXXValidator : AbstractValidator
    • public CreateXXXValidator() { Rules }

---

API Endpoint Response Conventions

Endpoint Type	Possible Response Codes	Code Short Description	Response Headers & Response Body
GET /collection (e.g., GET /api/users)	200 OK	Success. The request was successful, and the collection of resources is in the body.	Headers: Content-Type: application/json Body: A JSON array of the resources. This should be an empty array [] if no items are found, not a 404.
	400 Bad Request	The request included invalid parameters (e.g., an invalid filter or sort key).	Headers: Content-Type: application/problem+json Body: A JSON object detailing the error.
GET /collection/{id} (e.g., GET /api/users/123)	200 OK	Success. The specific resource was found and is in the body.	Headers: Content-Type: application/json Body: A single JSON object representing the resource.
	404 Not Found	Resource not found. The server could not find a resource matching the provided ID.	Headers: - Body: Typically empty, or a standard error object.
POST /collection (e.g., POST /api/users)	201 Created	Success (Best Practice). The resource was successfully created.	Headers: Location: /api/users/124 (URL to the new resource). Body: (Optional but recommended) A JSON representation of the newly created resource, including its server-generated ID.
	400 Bad Request	Validation failed. The request body contained invalid or missing data. [ApiController] does this automatically.	Headers: Content-Type: application/problem+json Body: A JSON object detailing the model validation errors.
	409 Conflict	The resource could not be created because it would create a conflict (e.g., a user with that email already exists).	Headers: - Body: A JSON object explaining the nature of the conflict.
PUT /collection/{id} (e.g., PUT /api/users/123)	204 No Content	Success (Best Practice). The resource was fully updated. No body is returned as the client already has the new state.	Headers: - Body: Empty.
	200 OK	Success (Alternative). The resource was updated, and the server is returning the updated representation.	Headers: Content-Type: application/json Body: The full, updated JSON object.
	404 Not Found	The resource to be updated could not be found.	Headers: - Body: Typically empty.
	400 Bad Request	The request body for the update was invalid.	Headers: Content-Type: application/problem+json Body: A JSON object detailing the validation errors.
DELETE /collection/{id} (e.g., DELETE /api/users/123)	204 No Content	Success. The resource was successfully deleted.	Headers: - Body: Empty.
	404 Not Found	The resource to be deleted could not be found.	Headers: - Body: Typically empty.

---

Common/General Response Codes

These codes can be returned by almost any endpoint.

Response Code	Code Short Description	When It's Used
401 Unauthorized	The client has not authenticated.	The request requires authentication, but no valid token (e.g., JWT Bearer token) was provided. The client should log in first.
403 Forbidden	The client is not allowed to perform this action.	The client is authenticated (logged in), but their role or permissions do not grant them access to this specific resource or action.
500 Internal Server Error	A generic, unhandled exception occurred on the server.	This indicates a bug in your API code. The response body should not expose sensitive details like stack traces in a production environment.

How to Implement This in .NET

• Ok(object) -> 200 OK with a body.
• CreatedAtAction("ActionName", routeValues, object) -> 201 Created with a Location header and a body.
• NoContent() -> 204 No Content.
• BadRequest(object) -> 400 Bad Request with a body detailing errors.
• NotFound() -> 404 Not Found.
• Conflict(object) -> 409 Conflict with a body.
• Forbid() -> 403 Forbidden.
• Unauthorized() -> 401 Unauthorized.