Tutorials ADO.NET Core Tutorial
Repository Pattern — Complete Guide
Repository Pattern — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of ADO.NET Core Tutorial on Toolliyo Academy.
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ADO.NET Core Tutorial · Lesson 53 of 100
Repository Pattern
Foundations ✓ → SQL & safety ✓ → Production → Projects
Production · 3 — ASP.NET & enterprise · ~10 min · Module 6: ASP.NET Core Integration
What is this?
IOrderRepository hides SqlConnection details; OrderRepository implements with ADO.NET.
Why should you care?
ShopNest tests mock the interface; production uses SQL.
See it live — copy this example
Use a .NET console or API project with SQL Server LocalDB. Run dotnet run after pasting.
public interface IOrderRepository
{
Task<IReadOnlyList<OrderDto>> GetPendingAsync(CancellationToken ct);
}
public sealed class OrderRepository(IConfiguration config) : IOrderRepository
{
private readonly string _cs = config.GetConnectionString("ShopNestDb")!;
public async Task<IReadOnlyList<OrderDto>> GetPendingAsync(CancellationToken ct) { /* SqlClient */ return []; }
}What happened?
- Interface in application layer; impl in infrastructure.
- Scoped DI.
Practice next
- Extract SQL into repo.
- AddScoped registration.
- Unit test with fake.
- Add GetByIdAsync.
- Throw if cs missing.
Remember
Interface + ADO.NET impl. Scoped lifetime. Testable.
ShopNest OrderRepository
All order SQL behind interface.
Outcome: Controllers stay thin.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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