dck-modern-csharp

name	dck-modern-csharp
description	Use when writing or reviewing AHKFlowApp C# for .NET 10, C# 14, primary constructors, records, patterns, or collections.

Modern C#

AHKFlowApp Defaults

• Use primary constructors for dependency injection.
• Use records for DTOs, commands, queries, and value objects.
• Use collection expressions ([]) instead of verbose collection initialization.
• Use sealed unless a class is designed for inheritance.
• Use TimeProvider instead of DateTime.Now or DateTime.UtcNow.
• Use file-scoped namespaces and Allman braces.
• Use var when the type is apparent.

Patterns

Feature	Use
Primary constructors	DI services, controllers, handlers
Records	DTOs, commands, queries, value objects
Collection expressions	Empty collections and small literals
Pattern matching	Result/state branching where it improves clarity
Raw string literals	JSON, SQL snippets, expected text blocks
required	Configuration options and input objects that must be initialized
field keyword	Property validation without manual backing fields when supported

Examples

public sealed record CreateHotstringCommand(CreateHotstringDto Input);

internal sealed class ListHotstringsHandler(AppDbContext db)
    : IUseCaseHandler<ListHotstringsQuery, Result<PagedList<HotstringDto>>>
{
    public async Task<Result<PagedList<HotstringDto>>> ExecuteAsync(
        ListHotstringsQuery request,
        CancellationToken cancellationToken)
    {
        var items = await db.Hotstrings
            .AsNoTracking()
            .OrderBy(x => x.Trigger)
            .ToListAsync(cancellationToken);

        return Result.Success(Map(items));
    }
}

string[] allowedExtensions = [".ahk", ".txt"];
List<Guid> selectedProfileIds = [defaultProfileId, .. request.ProfileIds];

Use With Restraint

Modern syntax is a tool, not a goal. Avoid deeply nested property/list patterns when simple local variables are clearer. Do not replace clear domain methods with clever expressions.

Anti-Patterns

• Traditional constructor plus _field = field ceremony for simple DI.
• Tuple types where a named record communicates intent.
• new List<T>() for simple empty or literal collections.
• Pattern matching that hides business rules.
• Nullable suppression without a clear invariant.
• Public setters on domain entity state.

Decision Guide

Scenario	Use
API request/response	sealed record
Handler/controller DI	Primary constructor
Domain state	private setters plus factory/domain methods
Small immutable value	readonly record struct when appropriate
Multi-line expected JSON	Raw string literal
Current time	TimeProvider.GetUtcNow()