Adding Result support

Author: ejsmith

samples/ConsoleSample/ConsoleSample.csproj

@@ -23,6 +23,7 @@
     <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="8.0.0" />
     <PackageReference Include="Microsoft.Extensions.Hosting" Version="8.0.0" />
     <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="8.0.0" />
+    <PackageReference Include="MiniValidation" Version="0.8.0" />
   </ItemGroup>
 
 </Project>

samples/ConsoleSample/Handlers/CreateUserCommandHandler.cs

@@ -0,0 +1,30 @@
+using ConsoleSample.Messages;
+using Foundatio.Mediator;
+
+public class CreateUserCommandHandler
+{
+    public async Task<Result<User>> HandleAsync(CreateUserCommand command, CancellationToken cancellationToken = default)
+    {
+        // Simulate some business logic
+        await Task.Delay(100, cancellationToken);
+
+        if (command.Email == "existing@example.com")
+            return Result.Conflict("A user with this email already exists");
+
+        // Create the user
+        var user = new User
+        {
+            Id = Random.Shared.Next(1000, 9999),
+            Name = command.Name,
+            Email = command.Email,
+            Age = command.Age,
+            PhoneNumber = command.PhoneNumber,
+            CreatedAt = DateTime.UtcNow
+        };
+
+        Console.WriteLine($"✅ [CreateUserCommandHandler] Successfully created user with ID: {user.Id}");
+
+        // User implicitly converted to Result<User>
+        return user;
+    }
+}

samples/ConsoleSample/Handlers/ValidationHandlers.cs

@@ -0,0 +1,36 @@
+using System.ComponentModel.DataAnnotations;
+using Foundatio.Mediator;
+
+namespace ConsoleSample.Messages;
+
+public class CreateUserCommand : ICommand
+{
+    [Required(ErrorMessage = "Name is required")]
+    [StringLength(50, MinimumLength = 2, ErrorMessage = "Name must be between 2 and 50 characters")]
+    public string Name { get; set; } = string.Empty;
+
+    [Required(ErrorMessage = "Email is required")]
+    [EmailAddress(ErrorMessage = "Invalid email format")]
+    public string Email { get; set; } = string.Empty;
+
+    [Range(18, 120, ErrorMessage = "Age must be between 18 and 120")]
+    public int Age { get; set; }
+
+    [Phone(ErrorMessage = "Invalid phone number format")]
+    public string? PhoneNumber { get; set; }
+}
+
+public record User
+{
+    public int Id { get; set; }
+    public string Name { get; set; } = string.Empty;
+    public string Email { get; set; } = string.Empty;
+    public int Age { get; set; }
+    public string? PhoneNumber { get; set; }
+    public DateTime CreatedAt { get; set; }
+}
+
+public record UserCreatedEvent(User User) : INotification
+{
+    public string Id => User.Id.ToString();
+}

samples/ConsoleSample/Messages/ValidationMessages.cs

@@ -0,0 +1,31 @@
+using Foundatio.Mediator;
+using MiniValidation;
+
+namespace ConsoleSample.Middleware;
+
+/// <summary>
+/// Validation middleware that uses MiniValidator to validate message models before handler execution.
+/// If validation fails, it short-circuits and returns validation errors as a Result.
+/// </summary>
+public class ValidationMiddleware
+{
+    /// <summary>
+    /// Validates the message before handler execution. If validation fails, returns a short-circuit result.
+    /// </summary>
+    /// <param name="message">The message to validate.</param>
+    /// <returns>A HandlerResult that either continues or short-circuits with validation errors.</returns>
+    public HandlerResult Before(object message)
+    {
+        if (!MiniValidator.TryValidate(message, out var errors))
+        {
+            // Convert MiniValidator errors to Foundatio.Mediator ValidationErrors
+            var validationErrors = errors.SelectMany(kvp =>
+                kvp.Value.Select(errorMessage =>
+                    new ValidationError(kvp.Key, errorMessage))).ToList();
+
+            return HandlerResult.ShortCircuit(Result.Invalid(validationErrors));
+        }
+
+        return HandlerResult.Continue();
+    }
+}

samples/ConsoleSample/Middleware/ValidationMiddleware.cs

@@ -13,6 +13,6 @@
 
 // Get mediator and run samples
 var mediator = host.Services.GetRequiredService<IMediator>();
-var sampleRunner = new SampleRunner(mediator);
+var sampleRunner = new SampleRunner(mediator, host.Services);
 
 await sampleRunner.RunAllSamplesAsync();

samples/ConsoleSample/Program.cs

@@ -1,15 +1,18 @@
 using ConsoleSample.Messages;
 using Foundatio.Mediator;
+using Microsoft.Extensions.DependencyInjection;
 
 namespace ConsoleSample;
 
 public class SampleRunner
 {
     private readonly IMediator _mediator;
+    private readonly IServiceProvider _serviceProvider;
 
-    public SampleRunner(IMediator mediator)
+    public SampleRunner(IMediator mediator, IServiceProvider serviceProvider)
     {
         _mediator = mediator;
+        _serviceProvider = serviceProvider;
     }
 
     public async Task RunAllSamplesAsync()
@@ -22,6 +25,7 @@ public async Task RunAllSamplesAsync()
         await RunPublishSamples();
         await RunSingleHandlerInvokeSamples();
         await RunMixedSyncAsyncSamples();
+        await RunValidationSamplesAsync();
 
         Console.WriteLine("🎉 All samples completed successfully!");
     }
@@ -94,4 +98,56 @@ private async Task RunMixedSyncAsyncSamples()
 
         Console.WriteLine("✅ Mixed sync/async test completed!\n");
     }
+
+    public async Task RunValidationSamplesAsync()
+    {
+        Console.WriteLine("\n🔍 === Validation Middleware Demonstration ===");
+        Console.WriteLine("This sample shows how validation middleware integrates with Result types");
+        Console.WriteLine("The middleware validates input before handlers run, returning validation errors as Results\n");
+
+        var createUserCommand = new CreateUserCommand
+        {
+            Name = "Sample User",
+            Email = "missing@example.com",
+            Age = 35,
+            PhoneNumber = "123-456-7890"
+        };
+
+        var userResult = await _mediator.InvokeAsync<Result<User>>(createUserCommand);
+        Console.WriteLine($"✅ User created successfully: {userResult.Value.Name}");
+
+        // asking for user will cause any errors to throw since the result type can't be implicitly converted to User
+        var user = await _mediator.InvokeAsync<User>(createUserCommand);
+        Console.WriteLine($"✅ User created successfully: {userResult.Value.Name}");
+
+        createUserCommand.Email = "existing@example.com";
+
+        userResult = await _mediator.InvokeAsync<Result<User>>(createUserCommand);
+        Console.WriteLine($"❌ User creation failed: {userResult.Errors}");
+
+        // asking for user will cause any errors to throw since the result type can't be implicitly converted to User
+        try
+        {
+            user = await _mediator.InvokeAsync<User>(createUserCommand);
+        }
+        catch (Exception ex)
+        {
+            Console.WriteLine($"❌ Error creating user: {ex.Message}");
+        }
+
+        createUserCommand.Email = String.Empty;
+
+        userResult = await _mediator.InvokeAsync<Result<User>>(createUserCommand);
+        Console.WriteLine($"❌ User creation failed: {userResult.Errors}");
+
+        // asking for user will cause any errors to throw since the result type can't be implicitly converted to User
+        try
+        {
+            user = await _mediator.InvokeAsync<User>(createUserCommand);
+        }
+        catch (Exception ex)
+        {
+            Console.WriteLine($"❌ Error creating user: {ex.Message}");
+        }
+    }
 }

samples/ConsoleSample/SampleRunner.cs

@@ -22,15 +22,6 @@ public static IServiceCollection ConfigureServices(this IServiceCollection servi
         // Register mediator and handlers
         services.AddMediator();
 
-        // Register middleware (no longer needed - middleware will be auto-created)
-        // services.AddScoped<ConsoleSample.Middleware.ProcessOrderMiddleware>();
-        // services.AddScoped<ConsoleSample.Middleware.GlobalMiddleware>();
-        // services.AddScoped<ConsoleSample.Middleware.CommandMiddleware>();
-        // services.AddScoped<ConsoleSample.Middleware.AnotherGlobalMiddleware>();
-        // services.AddScoped<ConsoleSample.Middleware.FirstOrderedMiddleware>();
-        // services.AddScoped<ConsoleSample.Middleware.LastOrderedMiddleware>();
-        // services.AddScoped<ConsoleSample.Middleware.SyncMiddleware>();
-
         return services;
     }
 }

samples/ConsoleSample/ServiceConfiguration.cs

@@ -0,0 +1,28 @@
+namespace Foundatio.Mediator;
+
+/// <summary>
+/// Defines the common interface for all Result types.
+/// </summary>
+public interface IResult
+{
+    /// <summary>
+    /// Gets the status of the result.
+    /// </summary>
+    ResultStatus Status { get; }
+
+    /// <summary>
+    /// Gets a value indicating whether the result represents a successful operation.
+    /// </summary>
+    bool IsSuccess { get; }
+
+    /// <summary>
+    /// Gets the type of the result value.
+    /// </summary>
+    Type ValueType { get; }
+
+    /// <summary>
+    /// Gets the result value as an object.
+    /// </summary>
+    /// <returns>The result value.</returns>
+    object? GetValue();
+}