ZenBlog Server

A RESTful blog API built with ASP.NET Core (.NET 10) following Clean Architecture principles. Features CQRS via MediatR, ASP.NET Core Identity, Entity Framework Core with PostgreSQL, a generic repository pattern, audit interceptors, and a FluentValidation pipeline.

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Table of Contents

• Architecture Overview
• Project Structure
• Tech Stack
• Domain Entities
• Features & Endpoints
• Authentication (JWT)
• Key Design Decisions
• Getting Started
• Configuration
• Running Migrations

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Architecture Overview

ZenBlog follows Clean Architecture with four layers that depend strictly inward:

┌─────────────────────────────────────────────┐
│            Presentation                     │
│            ZenBlog.API                      │  ← Minimal API endpoints, middleware
├─────────────────────────────────────────────┤
│            Infrastructure                  │
│            ZenBlog.Persistence             │  ← EF Core, Repositories, Migrations
│            ZenBlog.Infrastructure          │  ← JWT auth, current-user service
├─────────────────────────────────────────────┤
│            Core                             │
│            ZenBlog.Application             │  ← CQRS, Handlers, Validators, DTOs, Identity contracts
│            ZenBlog.Domain                  │  ← Entities, no dependencies
└─────────────────────────────────────────────┘

• Domain has zero dependencies — pure C# entities.
• Application depends only on Domain — no EF Core, no HTTP, no JWT library. It defines ports (IJwtTokenGenerator, ICurrentUserService) that outer layers implement.
• Persistence implements the persistence contracts — EF Core and PostgreSQL live here only.
• Infrastructure implements the identity/auth contracts — JWT creation and validation, current-user resolution.
• API wires everything together — minimal endpoints, middleware, no business logic.

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Project Structure

ZenBlogServer/
├── .github/
│   └── workflows/
├── Core/
│   ├── ZenBlog.Application/
│   │   ├── Base/
│   │   │   ├── BaseDto.cs
│   │   │   └── BaseResult.cs
│   │   ├── Behaviors/
│   │   │   └── ValidationBehavior.cs
│   │   ├── Contracts/
│   │   │   ├── Identity/
│   │   │   │   ├── ICurrentUserService.cs
│   │   │   │   └── IJwtTokenGenerator.cs
│   │   │   └── Persistence/
│   │   │       ├── IRepository.cs
│   │   │       └── IUnitOfWork.cs
│   │   ├── DTOs/
│   │   │   ├── BlogDto.cs
│   │   │   ├── CategoryDto.cs
│   │   │   └── UserDto.cs
│   │   ├── Extensions/
│   │   │   └── ServiceRegistration.cs
│   │   ├── Models/
│   │   │   └── JwtSettings.cs
│   │   └── Features/
│   │       ├── Auth/
│   │       │   ├── Commands/
│   │       │   │   └── LoginCommand.cs
│   │       │   ├── Handlers/
│   │       │   │   └── LoginCommandHandler.cs
│   │       │   ├── Results/
│   │       │   │   └── LoginResult.cs
│   │       │   └── Validators/
│   │       │       └── LoginValidator.cs
│   │       ├── Blogs/
│   │       │   ├── Commands/
│   │       │   │   ├── CreateBlogCommand.cs
│   │       │   │   ├── RemoveBlogCommand.cs
│   │       │   │   └── UpdateBlogCommand.cs
│   │       │   ├── Handlers/
│   │       │   │   ├── CreateBlogCommandHandler.cs
│   │       │   │   ├── GetBlogByIdQueryHandler.cs
│   │       │   │   ├── GetBlogsByCategoryIdQueryHandler.cs
│   │       │   │   ├── GetBlogsQueryHandler.cs
│   │       │   │   ├── RemoveBlogCommandHandler.cs
│   │       │   │   └── UpdateBlogCommandHandler.cs
│   │       │   ├── Mapping/
│   │       │   │   └── BlogMappingProfile.cs
│   │       │   ├── Queries/
│   │       │   │   ├── GetBlogByIdQuery.cs
│   │       │   │   ├── GetBlogsByCategoryIdQuery.cs
│   │       │   │   └── GetBlogsQuery.cs
│   │       │   ├── Results/
│   │       │   │   ├── CreateBlogResult.cs
│   │       │   │   └── GetBlogsQueryResult.cs
│   │       │   └── Validators/
│   │       │       ├── CreateBlogValidator.cs
│   │       │       └── UpdateBlogValidator.cs
│   │       ├── Categories/
│   │       │   ├── Commands/
│   │       │   │   ├── CreateCategoryCommand.cs
│   │       │   │   ├── RemoveCategoryCommand.cs
│   │       │   │   └── UpdateCategoryCommand.cs
│   │       │   ├── Handlers/
│   │       │   │   ├── CreateCategoryCommandHandler.cs
│   │       │   │   ├── GetCategoryByIdQueryHandler.cs
│   │       │   │   ├── GetCategoryQueryHandler.cs
│   │       │   │   ├── RemoveCategoryCommandHandler.cs
│   │       │   │   └── UpdateCategoryCommandHandler.cs
│   │       │   ├── Mapping/
│   │       │   │   └── CategoryMappingProfile.cs
│   │       │   ├── Queries/
│   │       │   │   ├── GetCategoryByIdQuery.cs
│   │       │   │   └── GetCategoryQuery.cs
│   │       │   ├── Results/
│   │       │   │   └── GetCategoryQueryResult.cs
│   │       │   └── Validators/
│   │       │       ├── CreateCategoryValidator.cs
│   │       │       └── UpdateCategoryValidator.cs
│   │       ├── Comments/
│   │       │   ├── Commands/
│   │       │   │   ├── CreateCommentCommand.cs
│   │       │   │   ├── RemoveCommentCommand.cs
│   │       │   │   └── UpdateCommentCommand.cs
│   │       │   ├── Handlers/
│   │       │   │   ├── CreateCommentCommandHandler.cs
│   │       │   │   ├── DeleteCommentCommandHandler.cs
│   │       │   │   ├── GetCommentByIdQueryHandler.cs
│   │       │   │   ├── GetCommentsByBlogIdQueryHandler.cs
│   │       │   │   └── UpdateCommentCommandHandler.cs
│   │       │   ├── Mapping/
│   │       │   │   └── CommentMappingProfile.cs
│   │       │   ├── Queries/
│   │       │   │   ├── GetCommentByIdQuery.cs
│   │       │   │   └── GetCommentsByBlogIdQuery.cs
│   │       │   ├── Results/
│   │       │   │   ├── CommentResult.cs
│   │       │   │   └── CreateCommentResult.cs
│   │       │   └── Validators/
│   │       │       ├── CreateCommentCommandValidation.cs
│   │       │       └── UpdateCommentCommandValidator.cs
│   │       └── Users/
│   │           ├── Commands/
│   │           │   └── CreateUserCommand.cs
│   │           ├── Handlers/
│   │           │   ├── CreateUserCommandHandler.cs
│   │           │   └── GetAllUsersQueryHandler.cs
│   │           ├── Mappings/
│   │           │   └── UserMappingProfile.cs
│   │           ├── Queries/
│   │           │   └── GetAllUsersQuery.cs
│   │           ├── Results/
│   │           │   ├── CreateUserResult.cs
│   │           │   └── GetAllUsersQueryResult.cs
│   │           └── Validators/
│   │               └── CreateUserCommandValidator.cs
│   └── ZenBlog.Domain/
│       ├── Entities/
│       │   ├── Common/
│       │   │   └── BaseEntity.cs
│       │   ├── AppRole.cs
│       │   ├── AppUser.cs
│       │   ├── Blog.cs
│       │   ├── Category.cs
│       │   ├── Comment.cs
│       │   ├── ContactInfo.cs
│       │   ├── Message.cs
│       │   └── SocialMedia.cs
│       └── ZenBlog.Domain.csproj
├── Infrastructure/
│   ├── ZenBlog.Infrastructure/
│   │   ├── Extensions/
│   │   │   └── ServiceRegistration.cs
│   │   ├── Identity/
│   │   │   ├── CurrentUserService.cs
│   │   │   └── JwtTokenGenerator.cs
│   │   └── ZenBlog.Infrastructure.csproj
│   └── ZenBlog.Persistence/
│       ├── Concrete/
│       │   ├── GenericRepository.cs
│       │   └── UnitOfWork.cs
│       ├── Context/
│       │   └── AppDbContext.cs
│       ├── Extentions/
│       │   └── ServiceRegistration.cs
│       ├── Intercepters/
│       │   └── AuditDbContextInterceptor.cs
│       ├── Migrations/
│       │   └── ...
│       └── ZenBlog.Persistence.csproj
└── Presentation/
    └── ZenBlog.API/
        ├── CustomMiddlewares/
        │   └── CustomExceptionHandlingMiddleware.cs
        ├── Endpoints/
        │   ├── AuthEndpoints.cs
        │   ├── BlogEndpoints.cs
        │   ├── CategoryEndpoints.cs
        │   ├── CommentEndpoints.cs
        │   ├── UserEndpoints.cs
        │   └── Registrations/
        │       └── EndpointRegistration.cs
        ├── Program.cs
        ├── appsettings.json
        ├── appsettings.Development.json
        └── ZenBlog.API.csproj

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Tech Stack

Concern	Library	Version
Framework	ASP.NET Core Minimal APIs	.NET 10
ORM	Entity Framework Core	10.0.8
Database	PostgreSQL via Npgsql	10.0.1
Identity	ASP.NET Core Identity + EF Core	10.0.8
Authentication	JWT Bearer (Microsoft.AspNetCore.Authentication.JwtBearer)	10.0.8
Token handling	System.IdentityModel.Tokens.Jwt	8.15.1
Lazy Loading	EF Core Proxies	10.0.8
CQRS / Mediator	MediatR	—
Object Mapping	AutoMapper	—
Validation	FluentValidation	—

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Domain Entities

AppUser

Extends IdentityUser<string> with FirstName, LastName, and ImageUrl. Owns blogs and comments.

AppRole

Extends IdentityRole<string> for role-based authorization.

Blog

Core content entity. Belongs to a Category and an AppUser. Has many Comments.

public class Blog : BaseEntity
{
    public string Title { get; set; }
    public string Description { get; set; }
    public string? CoverImageUrl { get; set; }
    public string? BlogImageUrl { get; set; }
    public Guid CategoryId { get; set; }
    public string UserId { get; set; }
    public virtual IList<Comment> Comments { get; set; }
}

Category

Groups blogs. One category has many blogs.

Comment

Self-referencing entity supporting threaded replies.

public class Comment : BaseEntity
{
    public string Body { get; set; }
    public Guid BlogId { get; set; }
    public string UserId { get; set; }
    public Guid? ParentCommentId { get; set; }  // null = top-level, set = reply
    public virtual IList<Comment> Replies { get; set; }
}

Other Entities

ContactInfo, Message, and SocialMedia support site management features.

BaseEntity

All domain entities inherit from BaseEntity which provides Id (Guid), CreatedAt, and UpdatedAt — automatically populated by AuditDbContextInterceptor on every save.

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Features & Endpoints

Auth

Method	Route	Description	Auth required
POST	/auth/login	Authenticate with email + password, returns a JWT	No

Users

Method	Route	Description	Auth required
POST	/users/register	Register a new user	No
GET	/users	Get all users	🔒 Yes

Blogs

Method	Route	Description	Auth required
GET	/blogs	Get all blogs with category	No
GET	/blogs/{id}	Get blog by ID	No
GET	/blogs/category/{categoryId}	Get blogs filtered by category	No
POST	/blogs	Create a blog	🔒 Yes
PUT	/blogs/{id}	Update a blog	🔒 Yes
DELETE	/blogs/{id}	Remove a blog	🔒 Yes

Categories

Method	Route	Description	Auth required
GET	/categories	Get all categories with blogs	No
GET	/categories/{id}	Get category by ID	No
POST	/categories	Create a category	🔒 Yes
PUT	/categories/{id}	Update a category	🔒 Yes
DELETE	/categories/{id}	Remove a category	🔒 Yes

Comments

Method	Route	Description	Auth required
GET	/comments/blog/{blogId}	Get top-level comments for a blog	No
GET	/comments/{id}	Get comment with its replies	No
POST	/comments	Create a comment or reply	🔒 Yes
PUT	/comments/{id}	Update comment body	🔒 Yes
DELETE	/comments/{id}	Remove a comment	🔒 Yes

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Authentication (JWT)

ZenBlog uses JWT Bearer authentication, implemented while preserving the Clean Architecture dependency rule: Application only knows about ports (interfaces); Infrastructure provides the actual implementation.

How the pieces fit together

Application (ports, no JWT library dependency)
  Contracts/Identity/IJwtTokenGenerator.cs   — "give me a token for this user"
  Contracts/Identity/ICurrentUserService.cs  — "who is calling right now"
  Models/JwtSettings.cs                      — plain POCO bound from configuration
  Features/Auth/                             — LoginCommand → LoginCommandHandler → LoginResult

Infrastructure (implements the ports)
  Identity/JwtTokenGenerator.cs   — builds the signed JWT (System.IdentityModel.Tokens.Jwt)
  Identity/CurrentUserService.cs — reads claims off HttpContext.User
  Extensions/ServiceRegistration.cs
      → binds JwtSettings
      → registers IJwtTokenGenerator / ICurrentUserService
      → configures the JwtBearer authentication scheme (validates incoming tokens)

Presentation
  Endpoints/AuthEndpoints.cs → POST /auth/login
  Program.cs → app.UseAuthentication() before app.UseAuthorization()
  .RequireAuthorization() on every mutating (POST/PUT/DELETE) endpoint

JwtTokenGenerator (creates tokens at login) and the AddJwtBearer(...) scheme configured in ServiceRegistration (validates tokens on every request) are two separate responsibilities that happen to share the same secret/issuer/audience.

Login flow

POST /auth/login  { "email": "...", "password": "..." }
        │
        ▼
LoginCommand → ValidationBehavior (email/password not empty)
        │
        ▼
LoginCommandHandler
   ├─ userManager.FindByEmailAsync(email)
   ├─ userManager.CheckPasswordAsync(user, password)
   ├─ userManager.GetRolesAsync(user)
   └─ tokenGenerator.GenerateToken(user, roles) → (token, expiresAtUtc)
        │
        ▼
200 OK { "userId": "...", "email": "...", "token": "eyJhbGciOi...", "expiresAtUtc": "..." }

A wrong email and a wrong password both return the same "Invalid email or password." message — this avoids leaking which one was incorrect (user-enumeration protection).

Trusting the token, not the request body

Handlers that create owned resources (CreateBlogCommandHandler, CreateCommentCommandHandler) inject ICurrentUserService and overwrite the entity's UserId with the authenticated caller's id, ignoring any UserId sent in the request body:

var blog = mapper.Map<Blog>(request);
blog.UserId = currentUser.UserId!;   // never trust a client-supplied UserId
await repository.CreateAsync(blog);

Setting the JWT secret (required before running)

The signing secret is never committed — it's stored in .NET User Secrets, the same way the database connection string is handled:

dotnet user-secrets set "JwtSettings:Secret" "<a random string, at least 32 characters>" --project Presentation/ZenBlog.API

Generate a proper random value rather than typing one by hand:

openssl rand -base64 32

Issuer, Audience, and ExpiryMinutes are non-secret and live in appsettings.json under JwtSettings (see Configuration).

Calling a protected endpoint

POST /auth/login              → copy "token" from the response
POST /blogs
  Header: Authorization: Bearer <token>

Requests to protected routes without a valid, non-expired token receive 401 Unauthorized.

---

Generic Repository with Include Support

IRepository<TEntity> exposes GetQuery() for flexible querying, plus two include-capable methods that keep EF Core out of the Application layer:

// All matching a filter with navigation properties loaded
Task<List<TEntity>> GetAllWithIncludesAsync(
    Expression<Func<TEntity, bool>> filter,
    CancellationToken ct,
    params Expression<Func<TEntity, object>>[] includes);

// Single entity with navigation properties loaded
Task<TEntity?> GetSingleWithIncludesAsync(
    Expression<Func<TEntity, bool>> filter,
    CancellationToken ct,
    params Expression<Func<TEntity, object>>[] includes);

Identity Users via UserManager

AppUser inherits from IdentityUser<string> — it cannot use IRepository<AppUser> due to the where TEntity : BaseEntity constraint. All user operations go through UserManager<AppUser>, which is Identity's own repository abstraction.

Flat DTOs to Prevent Circular References

Navigation properties in result DTOs use flat summary types (CategoryDto, BlogDto, UserDto) that never reference back to their parent — preventing infinite JSON serialization cycles:

Blog → GetBlogsQueryResult
         └── Category → CategoryDto  ✅ stops here, no Blogs list inside

Audit Interceptor

AuditDbContextInterceptor automatically sets CreatedAt and UpdatedAt on every SaveChanges call — handlers never set these manually.

CQRS with MediatR

Every operation is a Command (mutates state) or Query (reads state). Commands return minimal result records (CreateBlogResult, CreateCommentResult); queries return full result DTOs (GetBlogsQueryResult, CommentResult).

Validation Pipeline

FluentValidation validators run as a MediatR ValidationBehavior before any handler executes:

mediator.Send(command)
    → ValidationBehavior  ← short-circuits with errors if invalid
        → CommandHandler  ← only runs if validation passes

Global Exception Handling

CustomExceptionHandlingMiddleware catches all unhandled exceptions and returns a structured BaseResult error response — no handler needs a try/catch for unexpected errors.

BaseResult Envelope

All responses use a consistent envelope shape:

{
  "data": { "id": "...", "title": "..." },
  "errors": []
}

{
  "data": null,
  "errors": [{ "propertyName": "Email", "errorMessage": "Email is already in use." }]
}

---

Getting Started

Prerequisites

• .NET 10 SDK
• PostgreSQL server (local or remote)

Clone & Restore

git clone https://github.com/RoaaAlsham/ZenBlog.git
cd ZenBlog
dotnet restore

Update the connection string in appsettings.json (see Configuration), then:

dotnet ef database update \
  --project Infrastructure/ZenBlog.Persistence \
  --startup-project Presentation/ZenBlog.API

dotnet run --project Presentation/ZenBlog.API

The API will be available at https://localhost:7117.

---

Configuration

Presentation/ZenBlog.API/appsettings.json:

{
  "ConnectionStrings": {
    "DefaultConnection": "Host=localhost;Port=5432;Database=ZenBlogDb;Username=postgres;Password=yourpassword"
  },
  "JwtSettings": {
    "Issuer": "ZenBlogAPI",
    "Audience": "ZenBlogClient",
    "ExpiryMinutes": 60
  }
}

JwtSettings:Secret is not set here — like the connection string, it's kept out of source control via User Secrets:

dotnet user-secrets set "JwtSettings:Secret" "<a random string, at least 32 characters>" --project Presentation/ZenBlog.API

Without this, the app throws ArgumentNullException at startup when building the signing key.

---

Running Migrations

# Add a new migration
dotnet ef migrations add <MigrationName> \
  --project Infrastructure/ZenBlog.Persistence \
  --startup-project Presentation/ZenBlog.API

# Apply all pending migrations
dotnet ef database update \
  --project Infrastructure/ZenBlog.Persistence \
  --startup-project Presentation/ZenBlog.API

# Revert last migration
dotnet ef migrations remove \
  --project Infrastructure/ZenBlog.Persistence \
  --startup-project Presentation/ZenBlog.API