ASP.NET Core Project Anatomy: Program.cs and Middleware

Since .NET 6, ASP.NET Core uses a streamlined, minimal hosting model consolidated in Program.cs. Understanding the two phases—Service Registration and Middleware Pipeline Configuration—is critical.

1. The Anatomy of Program.cs

var builder = WebApplication.CreateBuilder(args);

// -------------------------------------------------------------
// 1. Configure Services (Dependency Injection Container)
// -------------------------------------------------------------
builder.Services.AddControllers();
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

// Add Database Context
builder.Services.AddDbContext<ApplicationDbContext>(options =>
    options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection")));

// Add CORS Policy for Angular client
builder.Services.AddCors(options =>
{
    options.AddPolicy("AngularDev", policy =>
    {
        policy.WithOrigins("http://localhost:4200")
              .AllowAnyHeader()
              .AllowAnyMethod()
              .AllowCredentials();
    });
});

var app = builder.Build();

// -------------------------------------------------------------
// 2. Configure HTTP Request Pipeline (Middleware Order Matters!)
// -------------------------------------------------------------
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();
app.UseRouting();

app.UseCors("AngularDev");

app.UseAuthentication();
app.UseAuthorization();

app.MapControllers();

app.Run();

2. The Critical Middleware Order

Middleware executes in the exact order it is registered: 1. UseExceptionHandler (Must catch all downstream errors) 2. UseHttpsRedirection 3. UseRouting 4. UseCors (Must precede Authentication/Authorization) 5. UseAuthentication 6. UseAuthorization 7. MapControllers