dotnet-backend

( options => options . UseNpgsql ( builder . Configuration . GetConnectionString ( "DefaultConnection" ) ) ) ; builder . Services . AddAuthentication ( ) . AddJwtBearer ( ) ; builder . Services . AddAuthorization ( ) ; var app = builder . Build ( ) ; // Create user endpoint app . MapPost ( "/api/users" , async ( CreateUserRequest request , AppDbContext db ) => { // Validate if ( string . IsNullOrEmpty ( request . Email ) ) return Results . BadRequest ( "Email is required" ) ; // Hash password var hashedPassword = BCrypt . Net . BCrypt . HashPassword ( request . Password ) ; // Create user var user = new User { Email = request . Email , PasswordHash = hashedPassword , Name = request . Name } ; db . Users . Add ( user ) ; await db . SaveChangesAsync ( ) ; return Results . Created ( $"/api/users/ { user . Id } " , new UserResponse ( user ) ) ; } ) . WithName ( "CreateUser" ) . WithOpenApi ( ) ; app . Run ( ) ; record CreateUserRequest ( string Email , string Password , string Name ) ; record UserResponse ( int Id , string Email , string Name ) ; Controller-based API [ ApiController ] [ Route ( "api/[controller]" ) ] public class UsersController : ControllerBase { private readonly AppDbContext _db ; private readonly ILogger < UsersController

_logger ; public UsersController ( AppDbContext db , ILogger < UsersController

logger ) { _db = db ; _logger = logger ; } [ HttpGet ] public async Task < ActionResult < List < UserDto

GetUsers ( ) { var users = await _db . Users . AsNoTracking ( ) . Select ( u => new UserDto ( u . Id , u . Email , u . Name ) ) . ToListAsync ( ) ; return Ok ( users ) ; } [ HttpPost ] public async Task < ActionResult < UserDto

CreateUser ( CreateUserDto dto ) { var user = new User { Email = dto . Email , PasswordHash = BCrypt . Net . BCrypt . HashPassword ( dto . Password ) , Name = dto . Name } ; _db . Users . Add ( user ) ; await _db . SaveChangesAsync ( ) ; return CreatedAtAction ( nameof ( GetUser ) , new { id = user . Id } , new UserDto ( user ) ) ; } } JWT Authentication using Microsoft . IdentityModel . Tokens ; using System . IdentityModel . Tokens . Jwt ; using System . Security . Claims ; using System . Text ; public class TokenService { private readonly IConfiguration _config ; public TokenService ( IConfiguration config ) => _config = config ; public string GenerateToken ( User user ) { var key = new SymmetricSecurityKey ( Encoding . UTF8 . GetBytes ( _config [ "Jwt:Key" ] ! ) ) ; var credentials = new SigningCredentials ( key , SecurityAlgorithms . HmacSha256 ) ; var claims = new [ ] { new Claim ( ClaimTypes . NameIdentifier , user . Id . ToString ( ) ) , new Claim ( ClaimTypes . Email , user . Email ) , new Claim ( ClaimTypes . Name , user . Name ) } ; var token = new JwtSecurityToken ( issuer : _config [ "Jwt:Issuer" ] , audience : _config [ "Jwt:Audience" ] , claims : claims , expires : DateTime . UtcNow . AddHours ( 1 ) , signingCredentials : credentials ) ; return new JwtSecurityTokenHandler ( ) . WriteToken ( token ) ; } } Background Service public class EmailSenderService : BackgroundService { private readonly ILogger < EmailSenderService

_logger ; private readonly IServiceProvider _services ; public EmailSenderService ( ILogger < EmailSenderService

logger , IServiceProvider services ) { _logger = logger ; _services = services ; } protected override async Task ExecuteAsync ( CancellationToken stoppingToken ) { while ( ! stoppingToken . IsCancellationRequested ) { using var scope = _services . CreateScope ( ) ; var db = scope . ServiceProvider . GetRequiredService < AppDbContext

( ) ; var pendingEmails = await db . PendingEmails . Where ( e => ! e . Sent ) . Take ( 10 ) . ToListAsync ( stoppingToken ) ; foreach ( var email in pendingEmails ) { await SendEmailAsync ( email ) ; email . Sent = true ; } await db . SaveChangesAsync ( stoppingToken ) ; await Task . Delay ( TimeSpan . FromMinutes ( 1 ) , stoppingToken ) ; } } private async Task SendEmailAsync ( PendingEmail email ) { // Send email logic _logger . LogInformation ( "Sending email to {Email}" , email . To ) ; } } Best Practices You Follow ✅ Async/await for all I/O operations ✅ Dependency Injection for all services ✅ appsettings.json for configuration ✅ User Secrets for local development ✅ Entity Framework migrations (Add-Migration, Update-Database) ✅ Global exception handling middleware ✅ FluentValidation for complex validation ✅ Serilog for structured logging ✅ Health checks (AddHealthChecks) ✅ API versioning ✅ Swagger/OpenAPI documentation ✅ AutoMapper for DTO mapping ✅ CQRS with MediatR (for complex domains) Limitations Assumes modern .NET (ASP.NET Core 8+); older .NET Framework projects may require different patterns. Does not cover client-side/frontend implementations. Cloud-provider-specific deployment details (Azure/AWS/GCP) are out of scope unless explicitly requested.