Can you give an example when a rollback or undo of a previous action was performed in a program or system?

An example of undo action in a C# program is the use of the "Command" pattern with undo support. For example, in a text editor:

public interface ICommand
{
    void Execute();
    void Undo();
}

public class InsertTextCommand : ICommand
{
    private StringBuilder _text;
    private string _insertedText;
    private int _position;

    public InsertTextCommand(StringBuilder text, string insertedText, int position)
    {
        _text = text;
        _insertedText = insertedText;
        _position = position;
    }

    public void Execute()
    {
        _text.Insert(_position, _insertedText);
    }

    public void Undo()
    {
        _text.Remove(_position, _insertedText.Length);
    }
}

Here, the Undo method cancels the text insertion action, restoring the state before the command was executed. This approach is often used to implement undo operations in applications and systems.