Tutorials ADO.NET Core Tutorial
SqlConnection — Complete Guide
SqlConnection — 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 6 of 100
SqlConnection
Foundations → SQL & safety → Production → Projects
Foundations · 1 — Connections & CRUD · ~6 min · Module 1: ADO.NET Fundamentals
What is this?
SqlConnection is one logical connection to SQL Server. OpenAsync borrows from the pool; dispose returns it.
Why should you care?
Leaked connections make ShopNest throw timeout expired under load.
See it live — copy this example
Use a .NET console or API project with SQL Server LocalDB. Run dotnet run after pasting.
await using var conn = new SqlConnection(cs);
await conn.OpenAsync(ct);
Console.WriteLine(conn.State); // Open
// commands here…
// dispose → back to poolWhat happened?
- await using always disposes.
- Prefer short lifetimes.
- Default Max Pool Size is 100.
Practice next
- Log State before/after Open.
- Wrap in await using.
- Pass CancellationToken.
- Force close with CloseAsync.
- Read ServerVersion.
Remember
Open → use → dispose. Pooling needs dispose. Pass ct.
ShopNest pool health
Repos open/dispose per call.
Outcome: Pool stays stable at sale traffic.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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