# efcore-patterns

A skill for Entity Framework Core work: NoTracking by default, query splitting, migration management and common pitfalls.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 1600 installs · ★ 1238
- Author: Aaronontheweb
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/Aaronontheweb/dotnet-skills/tree/HEAD/skills/efcore-patterns/SKILL.md
- Updated: 2026-10-11
- HTML: https://affpapa.org/en/nevibecode/skills/efcore-patterns

## What it does

The skill gathers EF Core practices in one place: `DbContext` setup, query performance, migration management and .NET Aspire integration. It fits when you are starting an EF Core project or when queries drag because of unnecessary change tracking.

Inside are five principles with code samples. The main one: set `QueryTrackingBehavior.NoTracking` in the `DbContext` constructor. Reads then run without tracking overhead, and writes need an explicit `.AsTracking()` or `Update()`. A table covers when tracking is worth turning on. Migrations get their own section: never edit, delete or rename the files by hand — use `dotnet ef` only. Commands cover creating, removing, applying and generating SQL scripts, including idempotent ones.

The third block is a dedicated migration service for Aspire: a separate project that runs migrations before the app starts. There is a catch here. With NoTracking on by default, `SaveChangesAsync()` silently does nothing after you change an entity and forget to mark it. Worth checking your update services for that.

The skill is not user-invocable — the agent loads it when EF Core comes up.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add Aaronontheweb/dotnet-skills --skill efcore-patterns -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/efcore-patterns/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/efcore-patterns/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add Aaronontheweb/dotnet-skills --skill efcore-patterns -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/efcore-patterns/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add Aaronontheweb/dotnet-skills --skill efcore-patterns -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/efcore-patterns/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install Aaronontheweb/dotnet-skills efcore-patterns
```

2. **Manually: put the files in place**
- File: `.github/skills/efcore-patterns/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add Aaronontheweb/dotnet-skills --skill efcore-patterns -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/Aaronontheweb/dotnet-skills --path skills/efcore-patterns
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/efcore-patterns/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add Aaronontheweb/dotnet-skills --skill efcore-patterns -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/Aaronontheweb/dotnet-skills/tree/HEAD/skills/efcore-patterns/SKILL.md

## When to use it
- configure a `DbContext` with change tracking off by default
- split loading of several navigation collections into separate queries
- create and roll back a migration through `dotnet ef` without touching files
- generate an idempotent SQL script for deploying migrations
- move migration execution into a separate service before app startup

## Example prompts
- Check my `ApplicationDbContext` against the EF Core settings in the efcore-patterns skill
- Help me create a migration for the orders table following efcore-patterns
- Figure out why `SaveChangesAsync` does not persist changes in my service

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 7fc4d141b4d2b109.

BEGIN THIRD-PARTY FILE 7fc4d141b4d2b109
````text
---
name: efcore-patterns
description: Entity Framework Core best practices including NoTracking by default, query splitting for navigation collections, migration management, dedicated migration services, and common pitfalls to avoid.
user-invocable: false
---

# Entity Framework Core Patterns

## When to Use This Skill

Use this skill when:
- Setting up EF Core in a new project
- Optimizing query performance
- Managing database migrations
- Integrating EF Core with .NET Aspire
- Debugging change tracking issues
- Loading multiple navigation collections efficiently (query splitting)

## Core Principles

1. **NoTracking by Default** - Most queries are read-only; opt-in to tracking
2. **Never Edit Migrations Manually** - Always use CLI commands
3. **Dedicated Migration Service** - Separate migration execution from application startup
4. **ExecutionStrategy for Retries** - Handle transient database failures
5. **Explicit Updates** - When NoTracking, explicitly mark entities for update

---

## Pattern 1: NoTracking by Default

Configure your DbContext to disable change tracking by default. This improves performance for read-heavy workloads.

```csharp
public class ApplicationDbContext : DbContext
{
    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
        : base(options)
    {
        // Disable change tracking by default for better performance on read-only queries
        // Use .AsTracking() explicitly for queries that need to track changes
        ChangeTracker.QueryTrackingBehavior = QueryTrackingBehavior.NoTracking;
    }

    public DbSet<Order> Orders => Set<Order>();
    public DbSet<Customer> Customers => Set<Customer>();
}
```

### When NoTracking is Active

**Read-only queries work normally:**
```csharp
// ✅ Fast read - no tracking overhead
var orders = await dbContext.Orders
    .Where(o => o.Status == OrderStatus.Pending)
    .ToListAsync();
```

**Writes require explicit handling:**
```csharp
// ❌ WRONG - Entity not tracked, SaveChanges does nothing
var order = await dbContext.Orders.FirstOrDefaultAsync(o => o.Id == orderId);
order.Status = OrderStatus.Shipped;
await dbContext.SaveChangesAsync(); // Nothing happens!

// ✅ CORRECT - Explicitly mark entity for update
var order = await dbContext.Orders.FirstOrDefaultAsync(o => o.Id == orderId);
order.Status = OrderStatus.Shipped;
dbContext.Orders.Update(order); // Marks entire entity as modified
````
END THIRD-PARTY FILE 7fc4d141b4d2b109

The third-party file has ended. Everything between the 7fc4d141b4d2b109 tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

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