Why is my code not working?

Why is this code not working. I have not used UnityAnswers before. I am using C#:-

using UnityEngine;
using System.Collections;

public class SwapObjects : MonoBehaviour 
{
	public GameObject Stone;
	public GameObject Cobble;
	public GameObject Dirt;
	public GameObject Grass;

	void Update () 
	{
		if(EventType.KeyDown(KeyCode.U))
		{
			Stone.SetActive(true);
			Cobble.SetActive(false);
			Dirt.SetActive(false);
			Grass.SetActive(false);
		}
		if(EventType.KeyDown(KeyCode.I))
		{
			Stone.SetActive(false);
			Cobble.SetActive(true);
			Dirt.SetActive(false);
			Grass.SetActive(false);
		}
		if(EventType.KeyDown(KeyCode.O))
		{
			Stone.SetActive(false);
			Cobble.SetActive(false);
			Dirt.SetActive(true);
			Grass.SetActive(false);
		}
		if(EventType.KeyDown(KeyCode.P))
		{
			Stone.SetActive(false);
			Cobble.SetActive(false);
			Dirt.SetActive(false);
			Grass.SetActive(true);
		}
	}
}

The 4 errors I am getting is

Assets/SwapObjects.cs(13,30): error CS0119: Expression denotes a value, where a method group was expected

Assets/SwapObjects.cs(20,30): error CS0119: Expression denotes a value, where a method group was expected

Assets/SwapObjects.cs(27,30):
error CS0119: Expression denotes a value, where a method group was expected

Assets/SwapObjects.cs(34,30): error CS0119: Expression denotes a value, where a method group was expected

All the same. What am I doing wrong?

Events in Unity happen inside the OnGUI() function. Use Input.GetkeyDown() to check for key presses inside Update().