feat: refactor validation behavior to use ErrorOr

Directory.Packages.props

@@ -13,7 +13,7 @@
         <PackageVersion Include="Microsoft.Extensions.Diagnostics.HealthChecks.EntityFrameworkCore" Version="8.0.1" />
         <!-- Open source packages -->
         <PackageVersion Include="CsvHelper" Version="15.0.10" />
-        <PackageVersion Include="ErrorOr" Version="1.6.0" />
+        <PackageVersion Include="ErrorOr" Version="1.10.0" />
         <PackageVersion Include="FluentValidation" Version="11.9.0" />
         <PackageVersion Include="FluentValidation.AspNetCore" Version="11.3.0" />
         <PackageVersion Include="MediatR" Version="12.2.0" />

requests/TodoItems/DeleteTodoItem.http

@@ -0,0 +1,9 @@
+@host = https://localhost:7098
+
+
+### Delete Todo itemId = 10 with wrong itemId. Check for 404 Not Found
+DELETE {{host}}/api/todo-items/10
+
+
+### Delete Todo itemId = 1, should return 204 No Content
+DELETE {{host}}/api/todo-items/1

requests/TodoItems/UpdateTodoItemDetails.http

@@ -0,0 +1,14 @@
+@host = https://localhost:7098
+@itemId = 4
+@listId = 1
+
+### Update Todo itemId = 1 with PriorityLevel = 1 and Note = "Updated Todo Item 1"
+PUT {{host}}/api/todo-items/UpdateItemDetails?id={{itemId}}
+Content-Type: application/json
+
+{
+    "id": {{itemId}},
+    "listId": {{listId}},
+    "priorityLevel": 1,
+    "note": "Updated Todo Item 1"
+}

requests/TodoLists/CreateTodoList.http

@@ -5,5 +5,21 @@ POST {{host}}/api/todo-lists
 Content-Type: application/json
 
 {
-  "title": "List 2"
+  "title": "List 1"
+}
+
+### Create Todo List item, validate that it handles empty title
+POST {{host}}/api/todo-lists
+Content-Type: application/json
+
+{
+  "title": ""
+}
+
+### Create Todo List item, validate that it duplicate title
+POST {{host}}/api/todo-lists
+Content-Type: application/json
+
+{
+  "title": "List 1"
 }

requests/TodoLists/DeleteTodoList.http

@@ -0,0 +1,9 @@
+@host = https://localhost:7098
+
+
+### Delete Todo itemId = 10 with wrong itemId. Check for 404 Not Found
+DELETE {{host}}/api/todo-lists/10
+
+
+### Delete Todo itemId = 1, should return 204 No Content
+DELETE {{host}}/api/todo-lists/1

src/Application/Common/ApiControllerBase.cs

@@ -1,6 +1,10 @@
+using ErrorOr;
+
 using MediatR;
 
+using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.ModelBinding;
 using Microsoft.Extensions.DependencyInjection;
 
 namespace VerticalSliceArchitecture.Application.Common;
@@ -12,4 +16,42 @@ public abstract class ApiControllerBase : ControllerBase
     private ISender? _mediator;
 
     protected ISender Mediator => _mediator ??= HttpContext.RequestServices.GetService<ISender>()!;
+
+    protected ActionResult Problem(List<Error> errors)
+    {
+        if (errors.Count is 0)
+        {
+            return Problem();
+        }
+
+        if (errors.All(error => error.Type == ErrorType.Validation))
+        {
+            return ValidationProblem(errors);
+        }
+
+        return Problem(errors[0]);
+    }
+
+    private ObjectResult Problem(Error error)
+    {
+        var statusCode = error.Type switch
+        {
+            ErrorType.Conflict => StatusCodes.Status409Conflict,
+            ErrorType.Validation => StatusCodes.Status400BadRequest,
+            ErrorType.NotFound => StatusCodes.Status404NotFound,
+            ErrorType.Unauthorized => StatusCodes.Status403Forbidden,
+            _ => StatusCodes.Status500InternalServerError,
+        };
+
+        return Problem(statusCode: statusCode, title: error.Description);
+    }
+
+    private ActionResult ValidationProblem(List<Error> errors)
+    {
+        var modelStateDictionary = new ModelStateDictionary();
+
+        errors.ForEach(error => modelStateDictionary.AddModelError(error.Code, error.Description));
+
+        return ValidationProblem(modelStateDictionary);
+    }
 }

src/Application/Common/Behaviours/ValidationBehaviour.cs

@@ -1,36 +1,40 @@
-using FluentValidation;
+using ErrorOr;
 
-using MediatR;
+using FluentValidation;
 
-using ValidationException = VerticalSliceArchitecture.Application.Common.Exceptions.ValidationException;
+using MediatR;
 
 namespace VerticalSliceArchitecture.Application.Common.Behaviours;
 
-public class ValidationBehaviour<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
-    where TRequest : IRequest<TResponse>
+public class ValidationBehavior<TRequest, TResponse>(IValidator<TRequest>? validator = null)
+    : IPipelineBehavior<TRequest, TResponse>
+        where TRequest : IRequest<TResponse>
+        where TResponse : IErrorOr
 {
-    private readonly IEnumerable<IValidator<TRequest>> _validators;
-
-    public ValidationBehaviour(IEnumerable<IValidator<TRequest>> validators)
-    {
-        _validators = validators;
-    }
+    private readonly IValidator<TRequest>? _validator = validator;
 
-    public async Task<TResponse> Handle(TRequest request, RequestHandlerDelegate<TResponse> next, CancellationToken cancellationToken)
+    public async Task<TResponse> Handle(
+        TRequest request,
+        RequestHandlerDelegate<TResponse> next,
+        CancellationToken cancellationToken)
     {
-        if (_validators.Any())
+        if (_validator is null)
         {
-            var context = new ValidationContext<TRequest>(request);
+            return await next();
+        }
 
-            var validationResults = await Task.WhenAll(_validators.Select(v => v.ValidateAsync(context, cancellationToken)));
-            var failures = validationResults.SelectMany(r => r.Errors).Where(f => f != null).ToList();
+        var validationResult = await _validator.ValidateAsync(request, cancellationToken);
 
-            if (failures.Count != 0)
-            {
-                throw new ValidationException(failures);
-            }
+        if (validationResult.IsValid)
+        {
+            return await next();
         }
 
-        return await next();
+        var errors = validationResult.Errors
+            .ConvertAll(error => Error.Validation(
+                code: error.PropertyName,
+                description: error.ErrorMessage));
+
+        return (dynamic)errors;
     }
 }

src/Application/ConfigureServices.cs

@@ -16,18 +16,17 @@ public static class DependencyInjection
 {
     public static IServiceCollection AddApplication(this IServiceCollection services)
     {
-        services.AddValidatorsFromAssembly(typeof(DependencyInjection).Assembly);
-
         services.AddMediatR(options =>
         {
             options.RegisterServicesFromAssembly(typeof(DependencyInjection).Assembly);
 
             options.AddOpenBehavior(typeof(AuthorizationBehaviour<,>));
-            options.AddOpenBehavior(typeof(ValidationBehaviour<,>));
             options.AddOpenBehavior(typeof(PerformanceBehaviour<,>));
-            options.AddOpenBehavior(typeof(UnhandledExceptionBehaviour<,>));
+            options.AddOpenBehavior(typeof(ValidationBehavior<,>));
         });
 
+        services.AddValidatorsFromAssembly(typeof(DependencyInjection).Assembly, includeInternalTypes: true);
+
         return services;
     }
 

src/Application/Features/TodoItems/CreateTodoItem.cs

@@ -1,4 +1,6 @@
-using FluentValidation;
+using ErrorOr;
+
+using FluentValidation;
 
 using MediatR;
 
@@ -13,13 +15,17 @@ namespace VerticalSliceArchitecture.Application.Features.TodoItems;
 public class CreateTodoItemController : ApiControllerBase
 {
     [HttpPost("/api/todo-items")]
-    public async Task<ActionResult<int>> Create(CreateTodoItemCommand command)
+    public async Task<IActionResult> Create(CreateTodoItemCommand command)
     {
-        return await Mediator.Send(command);
+        var result = await Mediator.Send(command);
+
+        return result.Match(
+            id => Ok(id),
+            Problem);
     }
 }
 
-public record CreateTodoItemCommand(int ListId, string? Title) : IRequest<int>;
+public record CreateTodoItemCommand(int ListId, string? Title) : IRequest<ErrorOr<int>>;
 
 internal sealed class CreateTodoItemCommandValidator : AbstractValidator<CreateTodoItemCommand>
 {
@@ -31,11 +37,11 @@ public CreateTodoItemCommandValidator()
     }
 }
 
-internal sealed class CreateTodoItemCommandHandler(ApplicationDbContext context) : IRequestHandler<CreateTodoItemCommand, int>
+internal sealed class CreateTodoItemCommandHandler(ApplicationDbContext context) : IRequestHandler<CreateTodoItemCommand, ErrorOr<int>>
 {
     private readonly ApplicationDbContext _context = context;
 
-    public async Task<int> Handle(CreateTodoItemCommand request, CancellationToken cancellationToken)
+    public async Task<ErrorOr<int>> Handle(CreateTodoItemCommand request, CancellationToken cancellationToken)
     {
         var entity = new TodoItem
         {

src/Application/Features/TodoItems/DeleteTodoItem.cs

@@ -1,9 +1,10 @@
-using MediatR;
+using ErrorOr;
+
+using MediatR;
 
 using Microsoft.AspNetCore.Mvc;
 
 using VerticalSliceArchitecture.Application.Common;
-using VerticalSliceArchitecture.Application.Common.Exceptions;
 using VerticalSliceArchitecture.Application.Domain.Todos;
 using VerticalSliceArchitecture.Application.Infrastructure.Persistence;
 
@@ -12,28 +13,38 @@ namespace VerticalSliceArchitecture.Application.Features.TodoItems;
 public class DeleteTodoItemController : ApiControllerBase
 {
     [HttpDelete("/api/todo-items/{id}")]
-    public async Task<ActionResult> Delete(int id)
+    public async Task<IActionResult> Delete(int id)
     {
-        await Mediator.Send(new DeleteTodoItemCommand(id));
+        var result = await Mediator.Send(new DeleteTodoItemCommand(id));
 
-        return NoContent();
+        return result.Match(
+            _ => NoContent(),
+            Problem);
     }
 }
 
-public record DeleteTodoItemCommand(int Id) : IRequest;
+public record DeleteTodoItemCommand(int Id) : IRequest<ErrorOr<Success>>;
 
-internal sealed class DeleteTodoItemCommandHandler(ApplicationDbContext context) : IRequestHandler<DeleteTodoItemCommand>
+internal sealed class DeleteTodoItemCommandHandler(ApplicationDbContext context) : IRequestHandler<DeleteTodoItemCommand, ErrorOr<Success>>
 {
     private readonly ApplicationDbContext _context = context;
 
-    public async Task Handle(DeleteTodoItemCommand request, CancellationToken cancellationToken)
+    public async Task<ErrorOr<Success>> Handle(DeleteTodoItemCommand request, CancellationToken cancellationToken)
     {
-        var entity = await _context.TodoItems
-            .FindAsync(new object[] { request.Id }, cancellationToken) ?? throw new NotFoundException(nameof(TodoItem), request.Id);
-        _context.TodoItems.Remove(entity);
+        var todoItem = await _context.TodoItems
+            .FindAsync([request.Id], cancellationToken);
+
+        if (todoItem is null)
+        {
+            return Error.NotFound(description: "Todo item not found.");
+        }
 
-        entity.DomainEvents.Add(new TodoItemDeletedEvent(entity));
+        _context.TodoItems.Remove(todoItem);
+
+        todoItem.DomainEvents.Add(new TodoItemDeletedEvent(todoItem));
 
         await _context.SaveChangesAsync(cancellationToken);
+
+        return Result.Success;
     }
 }