"The type or namespace name could not be found. Are you missing assembly reference ?" Error in Unity

Question

I am trying to show a GUI Label when mouse overs over an object and the label hides when mouse cursor is removed from object.

Can anyone please let me know why am i getting the error ?

using UnityEngine;
using System.Collections;

public class label_diet : MonoBehaviour {
    public showGUI boolean = false;
    void OnMouseOver()
    {
        showGUI = true;
    }

    void OnMouseExit()
    {
        showGUI = false;
    }

    void OnGUI()
    {
        if (showGUI)
        {
            GUI.Label(new Rect(10, 10, 100, 20), "You are selecting Diet coke");
        }
    }
}

Answer 1

Change the line that reads

public showGUI boolean = false;

To

public bool showGUI = false; //for C#
public var showGUI = false; //for JS, but you're using C#

That should work fine; if not, check that the script is attached either to a UI Object or an object with a collider component.