ADO.NET Basics

ADO.NET is the core .NET library for talking to databases. First, add the NuGet package:

Install-Package Microsoft.Data.SqlClient

The core objects

• SqlConnection — represents the connection to the database.
• SqlCommand — represents a SQL statement or stored procedure call.
• SqlParameter — a safely-typed value passed into a command (prevents SQL injection).
• SqlDataReader — reads results row-by-row, forward-only.

A minimal read example

using Microsoft.Data.SqlClient;

string connectionString = "Server=localhost\\SQLEXPRESS;Database=SchoolDB;Trusted_Connection=True;TrustServerCertificate=True;";

using var connection = new SqlConnection(connectionString);
connection.Open();

using var command = new SqlCommand("SELECT StudentId, FirstName, LastName FROM Students", connection);
using var reader = command.ExecuteReader();

while (reader.Read())
{
    int id = reader.GetInt32(0);
    string firstName = reader.GetString(1);
    string lastName = reader.GetString(2);
    Console.WriteLine($"{id}: {firstName} {lastName}");
}

Why "using"?

SqlConnection, SqlCommand, and SqlDataReader all hold unmanaged resources. The using keyword guarantees they're closed and disposed even if an exception occurs.