public async Task<int> InsertUserAsync(User user) { using var connection = new SqlConnection(_connectionString); var sql = "INSERT INTO Users (Username, Email) VALUES (@Username, @Email); SELECT CAST(SCOPE_IDENTITY() as int)"; return await connection.QuerySingleAsync<int>(sql, user); }
public static void CreateDatabase(string databaseName) { string createDbQuery = $@" CREATE DATABASE [{databaseName}] ON PRIMARY (NAME = N'{databaseName}', FILENAME = N'{Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)}\\{databaseName}.mdf') LOG ON (NAME = N'{databaseName}_log', FILENAME = N'{Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)}\\{databaseName}_log.ldf')"; using (var connection = new SqlConnection(ConnectionString)) { connection.Open(); using (var command = new SqlCommand(createDbQuery, connection)) { command.ExecuteNonQuery(); Console.WriteLine($"Database '{databaseName}' created successfully!"); } } } localdb mssqllocaldb
// DbContext class public class ApplicationDbContext : DbContext { public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options) : base(options) { } Check if Windows Firewall is blocking the connection");
public class User { public int Id { get; set; } public string Username { get; set; } public string Email { get; set; } public DateTime CreatedAt { get; set; } } // Check if LocalDB is running and accessible public static bool TestLocalDBConnection() { try { using var connection = new SqlConnection(@"Server=(localdb)\MSSQLLocalDB;Trusted_Connection=true;"); connection.Open(); Console.WriteLine("✓ LocalDB is accessible"); using var command = new SqlCommand("SELECT @@VERSION", connection); string version = command.ExecuteScalar().ToString(); Console.WriteLine($"✓ SQL Server Version: {version.Substring(0, Math.Min(50, version.Length))}..."); return true; } catch (Exception ex) { Console.WriteLine($"✗ Error connecting to LocalDB: {ex.Message}"); Console.WriteLine("\nTroubleshooting steps:"); Console.WriteLine("1. Run 'sqllocaldb start MSSQLLocalDB' in command prompt"); Console.WriteLine("2. Ensure SQL Server LocalDB is installed"); Console.WriteLine("3. Check if Windows Firewall is blocking the connection"); return false; } } Quick Start Summary # 1. Create and start LocalDB sqllocaldb create "MyApp" sqllocaldb start "MyApp" 2. Get connection string sqllocaldb info "MyApp" 3. Use in C# code "Server=(localdb)\MyApp;Database=MyDatabase;Trusted_Connection=true;" 4. Stop when done sqllocaldb stop "MyApp" Use in C# code "Server=(localdb)\MyApp
public async Task<IEnumerable<User>> GetUsersAsync() { using var connection = new SqlConnection(_connectionString); return await connection.QueryAsync<User>("SELECT * FROM Users"); }
// Attach a specific MDF file "Server=(localdb)\MSSQLLocalDB;AttachDbFileName=C:\Data\MyDatabase.mdf;Database=MyDatabase;Trusted_Connection=true;" # Check if LocalDB is installed sqllocaldb info Create a new LocalDB instance sqllocaldb create "MyInstance" Start the LocalDB instance sqllocaldb start "MyInstance" Get connection string for the instance sqllocaldb info "MyInstance" Stop the instance sqllocaldb stop "MyInstance" Delete the instance sqllocaldb delete "MyInstance" List all instances sqllocaldb i 3. C# - Create Database Programmatically using System.Data.SqlClient; public class LocalDBSetup { private const string ConnectionString = @"Server=(localdb)\MSSQLLocalDB;Trusted_Connection=true;";