Over the last few days, I sepent time refining architectural patterns in a modular .NET backend centered around payroll processing, approvals, and workflow-driven operations.

One area I focused on heavily was aggregate design and state protection. Instead of exposing mutable collections directly from entities, aggregates internally manage their own state exposing read-only access externally.

private readonly List _monthlyAllowance = new();

public IReadOnlyCollection

MonthlyAllowances => _monthlyAllowance ;

This prevents external code from bypassing aggregate rules;

employee.MonthlyAllowances.Add(...)

while still allowing controlled state transitions through aggregate methods:

public void AddMonthlyAllowance(MonthlyAllowance allowance)

{

if(_monthlyAllowances.Any(x => x.PayrollMonth == allowance.PayrollMonth && x.SalaryItemId == allowance.SalaryItemId))

{

throw new DuplicateMonthlyAllowanceException();

}

_monthlyAllowances.Add(allowance);

}

Another major refinement was moving workflow…