mediator.cs

public interface Button {
	void Click();
}

public interface Label {
	void setText(string text);
	string getText();
}

// TRADITIONAL

public class MyWindow {
	private HelloButton hello;
	private WorldButton world;
	private MyLabel label;
	
	public MyWindow() {
		label = new MyLabel();
		hello = new HelloButton(label);
		world = new WorldButton(world);
	}
}

public class HelloButton : Button {
	private MyLabel label;
	
	public HelloButton(MyLabel label) {
		this.label = label;
	}
	
	public void Click() {
		label.setText("Hello");
	}
}

public class WorldButton : Button {
	private MyLabel label;
	
	public WorldButton(MyLabel label) {
		this.label = label;
	}
	
	public void Click() {
		label.setText("World");
	}
}

public class MyLabel {
	private String text = "";
	
	public void setText(string text) {
		this.text = text;
	}
}

// MEDIATOR

public class MyWindow {//The mediator
	void onClickHello() {
		label.setText("Hello");
	}
	
	void onClickWorld() {
		label.setText("World");
	}
}

public class HelloButton : Button {
	MyWindow med;
	
	public void Click() {
		med.onClickHello();
	}
}

public class WorldButton : Button {
	MyWindow med;
	
	public void Click() {
		med.onClickWorld();
	}
}

// EVOLUTION: add checkbox for all capitals label

public interface Checkbox {
	public void Check(){}
	public void Uncheck(){}
}

public class CapitalsCheckbox : Checkbox {
	private MyWindow med;
	
	public void Check() {
		med.onCapitalsChecked();
	}
	public void Uncheck() {
		med.onCapitalsUnchecked();
	}
}

public class MyWindow {//The mediator
	private bool allCaps;
	private string originalLabelText;
	
	void onClickHello() {
		originalLabelText = "Hello";
		label.setText(allCaps ? "HELLO" : "Hello");
	}
	
	void onClickWorld() {
		originalLabelText = "World";
		label.setText(allCaps ? "WORLD" : "World");
	}
	void onCapitalsChecked() {
		allCaps = true;
		label.setText(originalLabelText.toUpperCase());
	}
	void onCapitalsUnchecked() {
		allCaps = false;
		label.setText(originalLabelText);
	}
}
// The mediator became a lot more complex, this will keep going on the more UI we add