C# Online Compiler | .NET Fiddle

using System;

public interface ICommand
{
	void Execute();
}

public class Button
{
	ICommand command;
	
	public Button(ICommand command)
	{
		this.command = command;
	}
	
	public void Click()
	{
		command.Execute();
	}
}

public class CustomerService
{
	public void AddCustomer() 
	{
		Console.WriteLine("Add Customer");
	}
}

public class AddCustomerCommand: ICommand
{
	private CustomerService service;
	
	public AddCustomerCommand(CustomerService service) 
	{
		this.service = service;
	}

	public void Execute() {
		service.AddCustomer();
	}
}


public class Program
{
	public static void Main()
	{
		var service = new CustomerService();
		var command = new AddCustomerCommand(service);
		var button = new Button(command);
		button.Click();
	}
}
Cached Result
result: 0.428571428571429