CODESAMPLE

Command - C#

Command C_sharp

The Command pattern encapsulates a request as an object, allowing parameterization of clients with different requests, queuing or logging of requests, and support for undoable operations. This implementation defines a base Command class with an Execute method. Concrete commands like FileSaveCommand and FileOpenCommand implement this interface, holding the necessary data to perform the action. An Invoker class stores and executes commands. This is idiomatic C# due to the use of interfaces for abstraction, delegates (implicitly used within the command’s execution) and clear separation of concerns, fitting well into the language’s object-oriented structure.

// Command Pattern in C#

// Receiver - The object that knows how to perform the action
public class FileSystemReceiver
{
    public string FilePath { get; set; }

    public void OpenFile(string filePath)
    {
        FilePath = filePath;
        Console.WriteLine($"Opening file: {filePath}");
    }

    public void SaveFile(string filePath)
    {
        FilePath = filePath;
        Console.WriteLine($"Saving file to: {filePath}");
    }
}

// Command Interface
public interface ICommand
{
    void Execute();
}

// Concrete Commands
public class FileOpenCommand : ICommand
{
    private readonly FileSystemReceiver _receiver;
    private readonly string _filePath;

    public FileOpenCommand(FileSystemReceiver receiver, string filePath)
    {
        _receiver = receiver;
        _filePath = filePath;
    }

    public void Execute()
    {
        _receiver.OpenFile(_filePath);
    }
}

public class FileSaveCommand : ICommand
{
    private readonly FileSystemReceiver _receiver;
    private readonly string _filePath;

    public FileSaveCommand(FileSystemReceiver receiver, string filePath)
    {
        _receiver = receiver;
        _filePath = filePath;
    }

    public void Execute()
    {
        _receiver.SaveFile(_filePath);
    }
}

// Invoker - Stores and executes commands
public class Menu
{
    private readonly List<ICommand> _commands = new List<ICommand>();

    public void AddCommand(ICommand command)
    {
        _commands.Add(command);
    }

    public void ExecuteCommand(int index)
    {
        if (index >= 0 && index < _commands.Count)
        {
            _commands[index].Execute();
        }
        else
        {
            Console.WriteLine("Invalid command index.");
        }
    }
}

// Client
public class Program
{
    public static void Main(string[] args)
    {
        FileSystemReceiver fileSystem = new FileSystemReceiver();
        Menu menu = new Menu();

        menu.AddCommand(new FileOpenCommand(fileSystem, "document.txt"));
        menu.AddCommand(new FileSaveCommand(fileSystem, "document.txt"));

        menu.ExecuteCommand(0); // Open file
        menu.ExecuteCommand(1); // Save file
    }
}