classlib/ExpenseTracker.Application/DependencyInjection.cs

using System.Reflection;
using FluentValidation;
using MediatR;
using MediatR.Behaviors.Authorization.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection;
using ExpenseTracker.Application.Common.Authorization;
using ExpenseTracker.Application.Common.Behaviours;

namespace ExpenseTracker.Application;

public static class DependencyInjection
{
    public static IServiceCollection AddApplication(this IServiceCollection services)
    {
        services
            .AddFluentValidation()
            .AddAutoMapper()
            .AddMediatR();

        return services;
    }

    private static IServiceCollection AddFluentValidation(this IServiceCollection services)
    {
        services.AddValidatorsFromAssembly(Assembly.GetExecutingAssembly());
        return services;
    }

    private static IServiceCollection AddAutoMapper(this IServiceCollection services)
    {
        services.AddAutoMapper(Assembly.GetExecutingAssembly());
        return services;
    }

    private static IServiceCollection AddMediatR(this IServiceCollection services)
    {
        // Adds the transient pipeline behavior and additionally registers all `IAuthorizationHandlers` for a given assembly
        services.AddMediatorAuthorization(
                Assembly.GetExecutingAssembly(),
                options => options.UseUnauthorizedResultHandlerStrategy(new CustomUnauthorizedResultHandler())
            );
        // Register all `IAuthorizer` implementations for a given assembly
        services.AddAuthorizersFromAssembly(Assembly.GetExecutingAssembly());

        services.AddMediatR(configuration =>
        {
            configuration.RegisterServicesFromAssembly(Assembly.GetExecutingAssembly());
            configuration.AddBehavior(typeof(IPipelineBehavior<,>), typeof(LoggingBehaviour<,>));
            configuration.AddBehavior(typeof(IPipelineBehavior<,>), typeof(ValidationBehaviour<,>));
        });

        return services;
    }
}