.NET 8 Coding Standards & Code Reviewer Checklist for Enterprise-Grade Web API Development

In the fast-paced world of enterprise software development, maintaining high-quality, scalable, and secure Web APIs is paramount. With the release of .NET 8, developers have access to powerful new features and enhancements that can elevate their APIs to enterprise-grade standards. This comprehensive guide dives deep into coding standards, best practices, and a practical code review checklist to ensure your .NET 8 Web APIs are robust, performant, and maintainable.

Whether you're building microservices, integrating with legacy systems, or exposing data to mobile and web clients, following these standards will help you avoid common pitfalls and deliver APIs that stand up to production demands. We'll explore everything from language conventions to observability, with real-world code samples and opinionated guidance on why each practice matters.

Language & Coding Standards

Establishing consistent coding standards from the outset prevents technical debt and improves team collaboration. In .NET 8, leverage built-in analyzers and configuration files to enforce these standards automatically.

Roslyn Analyzers and .editorconfig

Roslyn analyzers provide compile-time code analysis to catch issues early. Enable the full set of .NET analyzers in your project file:

<PropertyGroup>
  <EnableNETAnalyzers>true</EnableNETAnalyzers>
  <AnalysisLevel>latest</AnalysisLevel>
</PropertyGroup>

Use a comprehensive .editorconfig file to enforce style rules across your team:

root = true

[*]
charset = utf-8
end_of_line = lf
insert_final_newline = true
trim_trailing_whitespace = true

[*.cs]
dotnet_style_qualification_for_field = false:suggestion
dotnet_style_qualification_for_property = false:suggestion
dotnet_style_qualification_for_method = false:suggestion
dotnet_style_qualification_for_event = false:suggestion

csharp_style_var_for_built_in_types = true:suggestion
csharp_style_var_when_type_is_apparent = true:suggestion
csharp_style_var_elsewhere = false:suggestion

dotnet_style_readonly_field = true:suggestion

Why this matters: Consistent formatting reduces cognitive load during code reviews and prevents style-related conflicts in version control.

Async/Await Best Practices

Always use async/await for I/O-bound operations. Avoid blocking calls like .Result or .Wait():

// Good: Async all the way
public async Task<IActionResult> GetUserAsync(int id)
{
    var user = await _userService.GetUserAsync(id);
    return Ok(user);
}

// Bad: Blocking call
public IActionResult GetUser(int id)
{
    var user = _userService.GetUserAsync(id).Result; // Blocks thread
    return Ok(user);
}

Configure async method naming conventions in .editorconfig:

csharp_style_async_method_placement = all_on_same_line:suggestion
dotnet_naming_rule.async_methods_end_with_async.symbols = async_methods
dotnet_naming_rule.async_methods_end_with_async.style = end_with_async

Why this matters: Proper async usage prevents thread pool starvation and improves scalability under load.

API Design Best Practices

Well-designed APIs are intuitive, versioned, and self-documenting. Focus on RESTful principles while embracing modern standards.

RESTful Design and Versioning

Use URL-based versioning for clarity and backward compatibility:

[ApiController]
[Route("api/v{version:apiVersion}/[controller]")]
[ApiVersion("1.0")]
[ApiVersion("2.0")]
public class UsersController : ControllerBase
{
    [HttpGet("{id}")]
    [MapToApiVersion("1.0")]
    public async Task<IActionResult> GetUserV1(int id)
    {
        // Implementation
    }

    [HttpGet("{id}")]
    [MapToApiVersion("2.0")]
    public async Task<IActionResult> GetUserV2(int id)
    {
        // Enhanced implementation
    }
}

Register versioning in Program.cs:

builder.Services.AddApiVersioning(options =>
{
    options.DefaultApiVersion = new ApiVersion(1, 0);
    options.AssumeDefaultVersionWhenUnspecified = true;
    options.ReportApiVersions = true;
});

Why this matters: Proper versioning allows evolution without breaking existing clients.

Problem Details and OpenAPI/Swagger

Implement RFC 7807 Problem Details for consistent error responses:

public class ProblemDetailsExceptionHandler : IExceptionHandler
{
    public async ValueTask<bool> TryHandleAsync(
        HttpContext httpContext,
        Exception exception,
        CancellationToken cancellationToken)
    {
        var problemDetails = new ProblemDetails
        {
            Type = "https://tools.ietf.org/html/rfc7231#section-6.5.1",
            Title = "Internal Server Error",
            Detail = exception.Message,
            Status = StatusCodes.Status500InternalServerError,
            Instance = httpContext.Request.Path
        };

        httpContext.Response.StatusCode = problemDetails.Status.Value;
        await httpContext.Response.WriteAsJsonAsync(problemDetails, cancellationToken);

        return true;
    }
}

Register in Program.cs:

builder.Services.AddExceptionHandler<ProblemDetailsExceptionHandler>();
builder.Services.AddProblemDetails();

Add OpenAPI documentation:

builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen(options =>
{
    options.SwaggerDoc("v1", new OpenApiInfo { Title = "My API", Version = "v1" });
});

Why this matters: Standardized error responses improve client integration and debugging.

.NET 8 Middleware to Use

Leverage built-in middleware for caching, rate limiting, and cross-origin requests to enhance performance and security.

Output Caching and Rate Limiting

Implement output caching to reduce database load:

builder.Services.AddOutputCache(options =>
{
    options.AddBasePolicy(builder => builder.Expire(TimeSpan.FromMinutes(5)));
    options.AddPolicy("NoCache", builder => builder.NoCache());
});

app.UseOutputCache();

[HttpGet("users")]
[OutputCache(Duration = 300)]
public async Task<IActionResult> GetUsers()
{
    // Implementation
}

Add rate limiting to prevent abuse:

builder.Services.AddRateLimiter(options =>
{
    options.AddFixedWindowLimiter("fixed", opt =>
    {
        opt.Window = TimeSpan.FromSeconds(10);
        opt.PermitLimit = 5;
    });
});

app.UseRateLimiter();

Why this matters: Caching and rate limiting are essential for handling high-traffic scenarios and protecting against DoS attacks.

CORS Configuration

Configure CORS policies for secure cross-origin requests:

builder.Services.AddCors(options =>
{
    options.AddPolicy("AllowSpecificOrigins", builder =>
    {
        builder.WithOrigins("https://trusteddomain.com")
               .AllowAnyMethod()
               .AllowAnyHeader()
               .AllowCredentials();
    });
});

app.UseCors("AllowSpecificOrigins");

Why this matters: Proper CORS setup prevents unauthorized cross-origin requests while enabling legitimate ones.

Dependency Injection Patterns

Effective DI promotes loose coupling and testability. .NET 8 introduces keyed services for advanced scenarios.

Keyed Services in .NET 8

Use keyed services for multiple implementations of the same interface:

builder.Services.AddKeyedSingleton<ICacheService, RedisCacheService>("redis");
builder.Services.AddKeyedSingleton<ICacheService, InMemoryCacheService>("memory");

public class CacheController : ControllerBase
{
    public CacheController([FromKeyedServices("redis")] ICacheService cache)
    {
        // Use Redis cache
    }
}

Why this matters: Keyed services enable flexible configuration without complex factory patterns.

Security

Implement comprehensive security measures to protect your APIs and data.

JWT Bearer Authentication and OIDC

Configure JWT authentication:

builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
    .AddJwtBearer(options =>
    {
        options.Authority = "https://your-identity-provider.com";
        options.Audience = "your-api-audience";
        options.TokenValidationParameters = new TokenValidationParameters
        {
            ValidateIssuer = true,
            ValidateAudience = true,
            ValidateLifetime = true,
            ValidateIssuerSigningKey = true
        };
    });

builder.Services.AddAuthorization();

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

Why this matters: JWT and OIDC provide secure, scalable authentication for distributed systems.

HTTPS and Advanced CORS Rules

Enforce HTTPS in production:

if (!app.Environment.IsDevelopment())
{
    app.UseHsts();
}

app.UseHttpsRedirection();

Implement granular CORS policies:

builder.Services.AddCors(options =>
{
    options.AddPolicy("ApiCorsPolicy", builder =>
    {
        builder.WithOrigins("https://yourapp.com")
               .WithMethods("GET", "POST", "PUT", "DELETE")
               .WithHeaders("Authorization", "Content-Type")
               .SetPreflightMaxAge(TimeSpan.FromMinutes(10));
    });
});

Why this matters: HTTPS ensures encrypted communication, while precise CORS rules minimize attack surfaces.

EF Core 8 Modeling & Performance

Optimize data access with EF Core 8's advanced features.

Complex Types and Async Queries

Use complex types for value objects:

public class Address
{
    public string Street { get; set; }
    public string City { get; set; }
    public string ZipCode { get; set; }
}

public class User
{
    public int Id { get; set; }
    public string Name { get; set; }
    public Address HomeAddress { get; set; } // Complex type
}

Configure in DbContext:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<User>()
        .ComplexProperty(u => u.HomeAddress);
}

Implement efficient async queries with pagination:

public async Task<PagedResult<User>> GetUsersAsync(int page, int pageSize)
{
    var query = _context.Users.AsNoTracking();
    var totalCount = await query.CountAsync();
    
    var users = await query
        .OrderBy(u => u.Name)
        .Skip((page - 1) * pageSize)
        .Take(pageSize)
        .ToListAsync();
    
    return new PagedResult<User>(users, totalCount, page, pageSize);
}

Why this matters: Complex types reduce table proliferation, while async queries and pagination ensure scalability.

Resilience Patterns using Microsoft.Extensions.Http.Resilience

Build fault-tolerant HTTP clients with the new resilience pipeline.

HttpClient with Standard Resilience Handler

Configure resilient HttpClient:

builder.Services.AddHttpClient("ResilientClient")
    .AddStandardResilienceHandler(options =>
    {
        options.Retry.MaxRetryAttempts = 3;
        options.Retry.BackoffType = DelayBackoffType.Exponential;
        options.CircuitBreaker.FailureRatio = 0.5;
        options.CircuitBreaker.MinimumThroughput = 10;
    });

public class ExternalApiService
{
    private readonly HttpClient _httpClient;

    public ExternalApiService(IHttpClientFactory httpClientFactory)
    {
        _httpClient = httpClientFactory.CreateClient("ResilientClient");
    }

    public async Task<string> GetDataAsync()
    {
        var response = await _httpClient.GetAsync("https://api.example.com/data");
        return await response.Content.ReadAsStringAsync();
    }
}

Why this matters: Resilience patterns prevent cascading failures in distributed systems.

System.Text.Json in .NET 8

Leverage source generation and advanced serialization features.

Source Generation and Naming Policies

Use source-generated serializers for performance:

[JsonSerializable(typeof(User))]
[JsonSerializable(typeof(List<User>))]
public partial class UserJsonContext : JsonSerializerContext
{
}

builder.Services.ConfigureHttpJsonOptions(options =>
{
    options.SerializerOptions.TypeInfoResolverChain.Insert(0, UserJsonContext.Default);
});

Configure naming policies:

builder.Services.ConfigureHttpJsonOptions(options =>
{
    options.SerializerOptions.PropertyNamingPolicy = JsonNamingPolicy.CamelCase;
    options.SerializerOptions.DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull;
});

Why this matters: Source generation eliminates runtime reflection overhead, improving serialization performance.

Observability

Implement comprehensive monitoring for production troubleshooting.

OpenTelemetry Setup

Configure OpenTelemetry for traces, metrics, and logs:

builder.Services.AddOpenTelemetry()
    .WithTracing(tracerProviderBuilder =>
        tracerProviderBuilder
            .AddAspNetCoreInstrumentation()
            .AddHttpClientInstrumentation()
            .AddOtlpExporter())
    .WithMetrics(metricsProviderBuilder =>
        metricsProviderBuilder
            .AddAspNetCoreInstrumentation()
            .AddHttpClientInstrumentation()
            .AddOtlpExporter())
    .WithLogging(loggingBuilder =>
        loggingBuilder.AddOtlpExporter());

Why this matters: Observability enables proactive issue detection and performance optimization.

Health Checks

Implement health checks for monitoring application status.

builder.Services.AddHealthChecks()
    .AddDbContextCheck<ApplicationDbContext>()
    .AddUrlGroup(new Uri("https://api.example.com/health"), "External API");

app.MapHealthChecks("/health");

Why this matters: Health checks enable automated monitoring and quick failure detection.

Performance Tips

1. Use Response Caching: Cache frequently accessed data to reduce database load.
2. Implement Pagination: Never return large datasets without pagination.
3. Optimize EF Queries: Use AsNoTracking() for read-only operations and select only needed columns.
4. Leverage Async I/O: Ensure all I/O operations are truly asynchronous.
5. Use Connection Pooling: Configure database connection pooling appropriately.
6. Implement Compression: Enable response compression for text-based responses.
7. Profile Memory Usage: Monitor for memory leaks and optimize object allocations.
8. Use Background Services: Offload heavy computations to background tasks.

15-Minute Code Review Checklist

Use this checklist during code reviews to ensure enterprise-grade quality:

Architecture & Design

• [ ] API follows RESTful conventions
• [ ] Proper separation of concerns (controllers, services, repositories)
• [ ] Dependency injection used correctly
• [ ] No tight coupling between layers

Security

• [ ] Input validation implemented (data annotations, FluentValidation)
• [ ] Authentication and authorization properly configured
• [ ] Sensitive data not logged or exposed
• [ ] HTTPS enforced in production
• [ ] CORS policies configured appropriately

Performance

• [ ] Async/await used for all I/O operations
• [ ] EF queries optimized (AsNoTracking, Select, pagination)
• [ ] No N+1 query problems
• [ ] Caching implemented where appropriate
• [ ] Response compression enabled

Error Handling

• [ ] Global exception handling with ProblemDetails
• [ ] Appropriate HTTP status codes returned
• [ ] Sensitive error details not exposed to clients
• [ ] Logging includes sufficient context for debugging

Code Quality

• [ ] Naming conventions followed (.editorconfig compliance)
• [ ] Code formatting consistent
• [ ] No magic numbers or hardcoded strings
• [ ] Unit tests cover business logic
• [ ] Comments explain complex business rules

API Design

• [ ] OpenAPI/Swagger documentation complete
• [ ] API versioning implemented
• [ ] Request/response models properly defined
• [ ] Content negotiation handled correctly

Resilience & Observability

• [ ] HttpClient configured with resilience policies
• [ ] Health checks implemented
• [ ] Logging and telemetry configured
• [ ] Circuit breakers and retries implemented

.NET 8 Features

• [ ] Keyed services used where appropriate
• [ ] Output caching and rate limiting configured
• [ ] System.Text.Json source generation utilized
• [ ] Minimal APIs used for simple endpoints

By following these standards and using this checklist, your team can deliver .NET 8 Web APIs that are secure, performant, and maintainable. Remember, quality is not an accident—it's the result of intentional design and rigorous review processes. Start implementing these practices today to elevate your enterprise API development game.