Backend · Cursor
.NET 10 & C# 14 Cursor Rules (.mdc)
Generate .NET 10 and C# 14 Cursor rules enforcing Minimal APIs, primary constructors, file-scoped namespaces, and EF Core 10 query optimizations.
- Path
- .cursor/rules/csharp-dotnet-10.mdc
- Loads
- Glob pattern match
- Format
- Frontmatter MDC (.mdc)
- Used by
- Cursor
What this file tells the agent
.NET 10 is the current LTS. With C# 14 (the field keyword, extension members, null-conditional assignment) on top of primary constructors and collection expressions, idiomatic code looks very different from 2018. Models trained on older code still write nested namespaces, Startup.cs classes and unindexed EF Core queries.
- Use current C# features: primary constructors, collection expressions, file-scoped namespaces, C# 14's field keyword, and nullable reference types (#nullable enable).
- Structure lightweight microservices with ASP.NET Core Minimal APIs using typed route groups and TypedResults return values.
- Enforce AsNoTracking() on read-only EF Core queries to eliminate memory overhead from change trackers.
- Validate request payloads using FluentValidation or MiniValidation before executing business logic.
- Use IHttpClientFactory with typed resilience pipelines (Polly) for outbound HTTP calls.
Code to avoid, and what to write instead
The rule steers the agent away from the left and toward the right.
// Discouraged: Nested namespaces, missing AsNoTracking, untyped object returns
namespace App.Controllers
{
public class UsersController : Controller
{
[HttpGet]
public IActionResult GetUser(Guid id)
{
var user = _context.Users.Find(id); // Untracked query tracking all state!
return Ok(user);
}
}
}namespace App.Features.Users;
using Microsoft.AspNetCore.Http.HttpResults;
using Microsoft.EntityFrameworkCore;
public record CreateUserRequest(string Email, string FullName);
public record UserDto(Guid Id, string Email, string FullName);
public static class UserEndpoints
{
public static RouteGroupBuilder MapUserEndpoints(this RouteGroupBuilder group)
{
group.MapGet("/{id:guid}", async Task<Results<Ok<UserDto>, NotFound>> (Guid id, AppDbContext db) =>
{
var user = await db.Users
.AsNoTracking()
.Where(u => u.Id == id)
.Select(u => new UserDto(u.Id, u.Email, u.FullName))
.FirstOrDefaultAsync();
return user is not null ? TypedResults.Ok(user) : TypedResults.NotFound();
});
return group;
}
}Install it in one command
- 01
Go to your project root
The file goes at .cursor/rules/csharp-dotnet-10.mdc, relative to the root.
- 02
Download the file
Run the command on the right. It downloads this preset and writes the file.
- 03
Make sure it gets used
Cursor picks up rules in .cursor/rules/ automatically. This one attaches when files matching its globs are in the request, or when you @-mention it.
$ mkdir -p ".cursor/rules" && curl -fsSL "https://www.devscratchpad.tech/api/raw/cursor-rules/csharp-dotnet-10" -o ".cursor/rules/csharp-dotnet-10.mdc"
writes .cursor/rules/csharp-dotnet-10.mdc
.cursor/rules/csharp-dotnet-10.mdc
To write the file from your own code instead, use Read your code or Convert Legacy Rules in the editor above.
More for .NET 10 & C# 14 Minimal APIs
Questions
- Does this rulebook support both Minimal APIs and traditional Controllers?
- Yes, though it prioritizes .NET 10 Minimal APIs with typed results for reduced overhead and cleaner unit testing.
- Why is AsNoTracking required for EF Core reads?
- AsNoTracking prevents EF Core from allocating memory for entity snapshot tracking on queries that do not modify state.