Explain any one SOLID principle.

Question

Backbencher Developer · Answer

The Single Responsibility Principle says a module should have one reason to change. It does not mean every class must contain one method; unrelated policies should not be coupled.

Example:
public sealed class InvoiceService(
    IInvoiceRepository repository,
    IInvoiceRenderer renderer,
    IEmailSender email)
{
    public async Task SendAsync(Guid id, CancellationToken ct)
    {
        var invoice = await repository.GetAsync(id, ct);
        var document = renderer.Render(invoice);
        await email.SendAsync(invoice.CustomerEmail, document, ct);
    }
}

Persistence, rendering, and transport can change independently. Do not split cohesive domain rules into tiny classes mechanically; the goal is safer change, not maximum file count.

Explain any one SOLID principle.

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