Invoker (TextEditor):?

Short answer: The TextEditor class is the invoker that invokes commands. It holds a stack of commands (_commandHistory) and is responsible for executing and undoing commands. When a command is executed, it’s pushed onto the stack. The Undo() method pops the last executed command and undoes its action. public class TextEditor

Example code

{
private readonly Stack<ICommand> _commandHistory = new Stack<ICommand>(); public void ExecuteCommand(ICommand command)
{ command.Execute(); _commandHistory.Push(command); }
public void Undo()
{
if (_commandHistory.Count > 0)
{
var command = _commandHistory.Pop(); command.Undo(); }
}
}

Real-world example (ShopNest)

Use a GoF pattern in ShopNest only when it removes duplication or makes a change safer—explain the problem it solves in the interview.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.