Clean API Template

ASP.NET Core API using MediatR and FluentValidation to separate concerns with middleware for ValidationException error handling. Project contains template and sample ASP.NET Core application which is refactored classic ASP.NET Core API template (Weather Forecast App).

Important notes

• Core subfolder should be moved into separate Core.csproj class library
• Infrastructure subfolder should be moved into Infrastructure.csproj More info about Clean Architecture: https://jasontaylor.dev/clean-architecture-getting-started/

New project setup

1. Add NuGet packages

   dotnet add package MediatR
   dotnet add package MediatR.Extensions.Microsoft.DependencyInjection
   dotnet add package FluentValidation
   dotnet add package FluentValidation.DependencyInjectionExtensions
   

2. Copy/Create unit:

   • ValidationErrorHandlingMiddleware.cs - link
   • Recommendations:
     • extract ValidationPipelineBehavior class into the separate unit
     • move it into Core/Behaviors directory

3. Update Startup.cs:

   // Register method:
   services.AddTransient(typeof(IPipelineBehavior<,>), typeof(ValidationPipelineBehavior<,>));
   var assembly = typeof(Startup).Assembly;
   services.AddMediatR(assembly);
   services.AddValidatorsFromAssembly(assembly);
   // Configure method:
   app.UseMiddleware<ValidationErrorHandlingMiddleware>();

4. Add Mediator Request and Handler (rename Forecast to your domain subject)

   public class GetForecastQuery : IRequest<Forecast> { ... }
   public class GetForecastQueryHandler : IRequestHandler<GetForecastQuery, Forecast> { ... }

5. Add Fluent Validator

   public class GetForecastQueryValidator : AbstractValidator<GetForecastQuery> { ... }