umbrella-dotnet-scaffold-service

name	umbrella-dotnet-scaffold-service
description	Scaffold a logic service (interface, implementation, models) in the Core.Logic project, following the Umbrella ServiceBase pattern with Lazy<T> repo injection.

Scaffold Service

Purpose

Add a new service to the Core.<AppName>.Core.Logic project for domain logic that goes beyond simple data access -- for example, AI integrations, external API calls, file processing orchestration, or complex calculations. Controllers call repositories directly for CRUD; this Logic project is for work that is genuinely more complex than that.

Do not create per-entity wrapper services that only delegate to a repository — that logic belongs in the controller (or its lifecycle hooks / controller service for Pattern 2). This rule overrides anything the Discovery step suggests: if the target project contains existing thin wrapper services, they are a legacy deviation, not a pattern to replicate.

Layer boundary rule

Core.Logic must never reference Web-layer projects.

Service interfaces and implementations in Core.Logic must not import types from any *.Web.Models, *.Web.Shared.Models, or other Web-layer namespace. If a method needs custom input/output shapes, define them as plain record types in Services\<Domain>\Models\ (Step 1). If the types you need currently live in a Web.Models project, that is a signal to create dedicated Core.Logic models — not to import from Web.

Discovery (read these before writing anything)

1. Read 1-2 existing service implementations in Core\<AppName>.Core.Logic\Services\ to understand the subfolder structure, constructor patterns, and method conventions.
2. Read the corresponding interfaces in their Abstractions\ subfolder.
3. Read Core\<AppName>.Core.Logic\IServiceCollectionExtensions.cs to understand the DI registration structure.
4. Identify the layer-specific exception type (e.g., <AppName>CoreLogicException in Core\<AppName>.Core.Logic\Exceptions\).

---

Folder structure

Services are grouped by domain under Core\<AppName>.Core.Logic\Services\:

Services\
  <Domain>\
    Abstractions\
      I<ServiceName>.cs
    Models\
      <ModelName>.cs        (only if the service has its own result/request models)
    <ServiceName>.cs

Examples: Services\Careers\, Services\Industries\. Use the entity or feature name as the domain folder.

---

Step 1 -- Create result/request models (if needed)

Create model files in Services\<Domain>\Models\ only if the service returns or accepts types that do not already exist in the domain or shared projects. Simple services that return existing entity types or primitives do not need model files.

Models are plain record or class types with no base class:

namespace <AppName>.Core.Logic.Services.<Domain>.Models;

public sealed record <ModelName>(string Title, string Description);

---

Step 2 -- Create the interface

File location: Core\<AppName>.Core.Logic\Services\<Domain>\Abstractions\I<ServiceName>.cs

using <AppName>.Core.Logic.Services.<Domain>.Models;  // only if custom models are used

namespace <AppName>.Core.Logic.Services.<Domain>.Abstractions;

public interface I<ServiceName>
{
    Task<<ModelName>?> GetSomethingAsync(string input, CancellationToken cancellationToken = default);
    Task<IReadOnlyCollection<<ModelName>>> FindAllAsync(CancellationToken cancellationToken = default);
}

Rules:

• The interface is public (no base interface)
• Add explicit using directives for any model or enum types used in method signatures that are not covered by the project's global usings -- check existing interface files to see what is required
• using directives must not reference any namespace containing .Web. -- method signatures must only use types from Core.Logic, Core.Domain, Core.Common, or the BCL
• Every method is async with CancellationToken cancellationToken = default as the last parameter
• Return types follow the same conventions as repository interfaces: Task<T?> for single-or-null, Task<IReadOnlyCollection<T>> for lists

---

Step 3 -- Create the implementation

File location: Core\<AppName>.Core.Logic\Services\<Domain>\<ServiceName>.cs

using <AppName>.Core.Data.Repositories.Abstractions;
using <AppName>.Core.Logic.Exceptions;
using <AppName>.Core.Logic.Services.Abstractions;
using <AppName>.Core.Logic.Services.<Domain>.Abstractions;
using <AppName>.Core.Logic.Services.<Domain>.Models;

namespace <AppName>.Core.Logic.Services.<Domain>;

internal sealed class <ServiceName> : ServiceBase, I<ServiceName>
{
    private readonly Lazy<I<Entity>Repository> _<entity>Repository;
    private readonly IExternalService _externalService;

    public <ServiceName>(
        ILogger<<ServiceName>> logger,
        Lazy<I<Entity>Repository> <entity>Repository,
        IExternalService externalService)
        : base(logger)
    {
        _<entity>Repository = <entity>Repository;
        _externalService = externalService;
    }

    public async Task<<ModelName>?> GetSomethingAsync(string input, CancellationToken cancellationToken = default)
    {
        cancellationToken.ThrowIfCancellationRequested();
        Guard.IsNotNullOrEmpty(input);

        try
        {
            // access repo via .Value
            var entity = await _<entity>Repository.Value.FindByXxxAsync(input, cancellationToken: cancellationToken);

            if (entity is null)
                return null;

            return new <ModelName>(entity.Title, entity.Description);
        }
        catch (Exception exc) when (Logger.WriteError(exc, new { input }))
        {
            throw new <AppName>CoreLogicException("There was a problem getting the <thing> with the specified input.", exc);
        }
    }
}

Rules:

• Always internal sealed class inheriting ServiceBase and the interface
• Constructor: ILogger<T> is the first parameter (passed to : base(logger)); remaining params are stored as private readonly fields
• Repositories are injected as Lazy<IRepository> and accessed via .Value inside methods
• Direct (non-repository) services are injected normally, not wrapped in Lazy<T>
• Add using directives for all namespaces that are not covered by the project's implicit or global usings -- follow the pattern of existing service files in the same project

---

Step 4 -- Write service methods

Every method follows this structure:

public async Task<T> DoWorkAsync(string input, CancellationToken cancellationToken = default)
{
    cancellationToken.ThrowIfCancellationRequested();
    Guard.IsNotNullOrEmpty(input);  // Guard.IsNotNull for non-string reference types; omit for value types

    try
    {
        // logic here -- call repos via .Value, call external services, build results
        return result;
    }
    catch (Exception exc) when (Logger.WriteError(exc, new { input }))
    {
        throw new <AppName>CoreLogicException("There was a problem doing the work.", exc);
    }
}

Rules:

• First line always: cancellationToken.ThrowIfCancellationRequested();
• Validate string inputs with Guard.IsNotNullOrEmpty(param) (Logic project uses IsNotNullOrEmpty, not IsNotNullOrWhiteSpace as in Data)
• The anonymous object in Logger.WriteError should contain the method's significant input parameters (omit cancellationToken)
• Re-throw as <AppName>CoreLogicException
• If integrating with an external API or service that may fail transiently, consider wrapping the call in a retry policy if one exists in the project (e.g., AiPolicyHelper.RetryPolicy.ExecuteAsync(...))

---

Step 5 -- Register in DI

File: Core\<AppName>.Core.Logic\IServiceCollectionExtensions.cs

Add one line in the // Services section, in alphabetical order:

_ = services.AddScoped<I<ServiceName>, <ServiceName>>();

Services are always AddScoped. File handlers are AddSingleton -- but those are covered by a separate skill.

---

Verification

1. Confirm the interface is public, has no base interface, and every method ends with CancellationToken cancellationToken = default.
2. Confirm the implementation is internal sealed, inherits ServiceBase and the interface, and ILogger<T> is the first constructor parameter passed to : base(logger).
3. Confirm repositories are Lazy<IRepository> and accessed via .Value inside methods.
4. Confirm every method calls cancellationToken.ThrowIfCancellationRequested() first, validates string inputs with Guard, and re-throws as <AppName>CoreLogicException.
5. Confirm AddScoped<I<ServiceName>, <ServiceName>>() is present in IServiceCollectionExtensions.cs.