SOLID & Design Patterns Interview Question #147

How would you prevent controllers from becoming too large?

Anti-Patterns, Refactoring, DI Lifetimes & Senior Design Scenarios Senior Advanced

Quick Interview Answer

Keep controllers focused on HTTP concerns: receiving input, invoking an application use case, and translating the result into an HTTP or view response. Move business rules to domain/application components and data access to repositories or query services where appropriate.

Detailed Explanation

Model binding, filters, middleware, mediator handlers, and application services can remove unrelated concerns, but avoid creating pass-through layers that add no meaningful boundary.

Code Example

public async Task<IActionResult> Confirm(Guid id)
{
    var result = await _orders.ConfirmAsync(id);

    return result.IsSuccess
        ? RedirectToAction("Details", new { id })
        : BadRequest(result.Error);
}