This document details the concrete Aspect-Oriented Programming (AOP) implementations used in the UMS API. These aspects are built on top of the Ums.Shell.Aop library and serve to decouple cross-cutting concerns from the core business logic (Commands and Queries) in the Application layer.
To automatically log the entry, success, failure, and execution duration of Application layer handlers.
Manually injecting ILogger<T> into every MediatR handler adds boilerplate and leads to inconsistent logging formats. By using an aspect, we guarantee that all operations are uniformly traced, making it easier to parse logs in centralized observatories like Datadog or ELK.
Apply the [LoggerAspect] attribute to any command or query handler.
using Ums.Application.Common.Aop;
[LoggerAspect(Type = typeof(IUmsLogger), LogDuration = true, LogException = true, LogArguments = [])]
public class CreateUserAccountCommandHandler : IRequestHandler<CreateUserAccountCommand, Result>
{
public async Task<Result> Handle(CreateUserAccountCommand request, CancellationToken cancellationToken)
{
// Business logic runs here. Logging is handled automatically.
return Result.Success();
}
}
To persist immutable records of critical state mutations to meet enterprise compliance and security standards.
Audit trails must never be bypassed by developers. Handling them via AOP ensures that every mutative operation (e.g., Create, Update, Delete) automatically resolves the affected entities, the actor, and the outcome (Success/Failure) and writes it to the Audit Sink without polluting the domain logic.
The AuditTrailAspect is registered globally in the Infrastructure layer using AddAop(). It automatically intercepts handlers decorated with [AuditTrailAttribute].
using Ums.Application.Common.Aop;
[AuditTrailAttribute(EventType = "UserCreation", WhatChanged = "Created a new user account")]
public class CreateUserAccountCommandHandler : IRequestHandler<CreateUserAccountCommand, Result>
{
public async Task<Result> Handle(CreateUserAccountCommand request, CancellationToken cancellationToken)
{
// Audit record is dispatched transparently upon successful completion
return Result.Success();
}
}
To wrap database operations within a robust Unit of Work / Transaction scope, ensuring atomic commits and automatic rollbacks upon failure.
Database transactions are an infrastructural concern. Forcing the application layer to manually manage IUnitOfWorkScope.BeginAsync(), CommitAsync(), and RollbackAsync() clutters the code and risks dangling transactions if exceptions are not properly caught.
Apply the [TransactionAspect] attribute to command handlers that write to the database.
using Ums.Application.Common.Aop;
[TransactionAspect]
public class UpdateSystemSuiteCommandHandler : IRequestHandler<UpdateSystemSuiteCommand, Result>
{
public async Task<Result> Handle(UpdateSystemSuiteCommand request, CancellationToken cancellationToken)
{
// If this method throws, or if it returns Result.Failure, the transaction rolls back.
// If it succeeds, the transaction is automatically committed.
await _repository.UpdateAsync(suite);
return Result.Success();
}
}
To enforce multi-tenancy boundaries at the outermost edges of the Application layer before domain logic is executed.
Relying solely on SQL Server RLS (Row-Level Security) is insufficient as a primary defense (Rule 7). The application must proactively validate that the incoming payload’s TenantId matches the authenticated session’s TenantId (from IUserContext), blocking malicious cross-tenant data requests instantly.
Apply the [TenantValidationAspect] attribute to handlers processing tenant-scoped data. The aspect intercepts the payload, extracts the TenantId using reflection, and verifies it against IUserContext.
using Ums.Application.Common.Aop;
[TenantValidationAspect]
public class GetUserAccountByIdQueryHandler : IRequestHandler<GetUserAccountByIdQuery, Result<UserAccountDto>>
{
public async Task<Result<UserAccountDto>> Handle(GetUserAccountByIdQuery request, CancellationToken cancellationToken)
{
// Aspect ensures request.TenantId == _userContext.TenantId.
// If they differ, an UnauthorizedAccessException is thrown before reaching here.
var user = await _repository.GetByIdAsync(request.Id);
return Result<UserAccountDto>.Success(user);
}
}