ASP.NET Core Reference & Cheatsheet

DodaTech Updated Jun 6, 2026 3 min read

Learning Path

    flowchart LR
    A["Aspnet Overview"] --> B["Core Concepts"]
    B --> C["Intermediate Topics"]
    C --> D["Advanced Topics"]
    D --> E["Practical Applications"]
    A --> F["You Are Here"]
    style F fill:#f90,color:#fff

A comprehensive reference for ASP.NET Core development — middleware pipeline, DI patterns, Entity Framework Core, controller conventions, and security best practices.

Program.cs Setup

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddControllers();
builder.Services.AddDbContext<AppDbContext>(options =>
    options.UseSqlServer(builder.Configuration.GetConnectionString("Default")));
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();

if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();
app.UseAuthorization();
app.MapControllers();
app.Run();

Controller Example

[ApiController]
[Route("api/[controller]")]
public class ProductsController : ControllerBase
{
    private readonly AppDbContext _db;

    public ProductsController(AppDbContext db)
    {
        _db = db;
    }

    [HttpGet]
    public async Task<ActionResult<List<Product>>> GetAll()
    {
        return await _db.Products.ToListAsync();
    }

    [HttpGet("{id}")]
    public async Task<ActionResult<Product>> GetById(int id)
    {
        var product = await _db.Products.FindAsync(id);
        if (product == null) return NotFound();
        return product;
    }

    [HttpPost]
    public async Task<ActionResult<Product>> Create(Product product)
    {
        _db.Products.Add(product);
        await _db.SaveChangesAsync();
        return CreatedAtAction(nameof(GetById), new { id = product.Id }, product);
    }
}

Entity Framework Core

public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
    public int CategoryId { get; set; }
    public Category Category { get; set; }
}

public class AppDbContext : DbContext
{
    public DbSet<Product> Products { get; set; }
    public DbSet<Category> Categories { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Product>()
            .Property(p => p.Price)
            .HasPrecision(18, 2);
    }
}

Middleware Pipeline Order

Exception handling (UseExceptionHandler)
HTTPS redirection (UseHttpsRedirection)
Static files (UseStaticFiles)
Routing (UseRouting)
CORS (UseCors)
Authentication (UseAuthentication)
Authorization (UseAuthorization)
Endpoints (MapControllers)

Dependency Injection

// Service lifetimes
builder.Services.AddScoped<IProductService, ProductService>();    // Per request
builder.Services.AddSingleton<ICacheService, MemoryCacheService>(); // Single instance
builder.Services.AddTransient<IEmailService, EmailService>();      // New each time

// Constructor injection
public class ProductService : IProductService
{
    private readonly AppDbContext _db;
    private readonly ILogger<ProductService> _logger;

    public ProductService(AppDbContext db, ILogger<ProductService> logger)
    {
        _db = db;
        _logger = logger;
    }
}

Common Configurations

// CORS
builder.Services.AddCors(options =>
{
    options.AddPolicy("AllowFrontend", policy =>
        policy.WithOrigins("https://myapp.com")
              .AllowAnyHeader()
              .AllowAnyMethod());
});

// JWT Authentication
builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
    .AddJwtBearer(options =>
    {
        options.TokenValidationParameters = new TokenValidationParameters
        {
            ValidateIssuer = true,
            ValidateAudience = true,
            ValidateLifetime = true,
            ValidIssuer = builder.Configuration["Jwt:Issuer"],
            ValidAudience = builder.Configuration["Jwt:Audience"],
            IssuerSigningKey = new SymmetricSecurityKey(
                Encoding.UTF8.GetBytes(builder.Configuration["Jwt:Key"]))
        };
    });

Common Mistakes

Assuming all features work identically — always check browser/version compatibility.
Skipping documentation — reference docs exist for a reason; consult them.
Not testing edge cases — your setup may differ from tutorials.
Overlooking security — always validate inputs and follow best practices.
Copy-pasting without understanding — type code yourself to build real knowledge.

What’s Next

Lesson	Description
https://tutorials.dodatech.com/backend/nodejs/express/	Express.js framework
https://tutorials.dodatech.com/backend/ror/reference/	Ruby on Rails reference
C#	C# programming language
.NET	.NET platform overview
Entity Framework	EF Core deep dive

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