congiuluc/repository-efcore

Repository Pattern — Entity Framework Core

When to Use

• Creating or modifying IRepository<T> interface or EF Core implementations
• Adding new entity types that need persistence via EF Core
• Configuring EF Core database providers (SQLite, SQL Server, PostgreSQL, Cosmos DB EF provider)
• Writing database migrations
• Registering EF Core repositories in DI
• Need LINQ support, change tracking, or complex relational queries

When to Use Dapper Instead

• Performance-critical read queries (reporting, dashboards)
• Scenarios requiring raw SQL or stored procedures
• Lightweight read models that don't need change tracking
• Use the repository-dapper skill for those cases

Official Documentation

• EF Core — Getting Started
• EF Core SQLite Provider
• EF Core SQL Server Provider
• EF Core PostgreSQL Provider (Npgsql)
• EF Core Cosmos DB Provider
• Azure Cosmos DB .NET SDK
• Repository Pattern
• EF Core Migrations
• EF Core Performance

Procedure

1. Define entity in Core with string Id property — see domain models
2. If new interface methods needed, extend IRepository<T> in Core
3. Create EF Core implementation: EF Core implementation
4. For Cosmos DB direct SDK access: Cosmos DB implementation
5. Register via DI configuration switching
6. Review sample repository for complete pattern
7. Write tests for the implementation
8. Run EF Core migrations for schema changes

Key Principles

• Use AsNoTracking() for read-only queries — avoids change tracking overhead
• Use ConfigureAwait(false) in all async repository methods
• Always accept CancellationToken in repository methods
• Use IReadOnlyList<T> for collection returns — prevent mutation by callers
• Keep DbContext scoped per request; CosmosClient as singleton
• Generate IDs in the repository layer (GUID) if not provided by the caller
• Never expose DbContext outside Infrastructure layer