C#

private void panel1_MouseWheel(object sender, MouseEventArgs e)<br />
{<br />
 MessageBox.Show("MouseWheel event now activated", "MouseWheel", MessageBoxButtons.OK, MessageBoxIcon.Information);<br />
}

<br />
// File: SetInterface.cs<br />
// Set ADT Specification<br />
using System;<br />
namespace SetInterface<br />
{<br />
	// invariant: Cardinality >= 0<br />
	public interface ISet<br />
	{<br />
		// Pre: true<br />
		// Post: return the cardinality of the set<br />
		int Cardinality {get;}<br />
<br />
		// Pre: true<br />
		// Post: Object element is contained in the set and the <br />
//	   cardinality increases by 1<br />
		void Add(Object element);<br />
<br />
		// Pre: Object element is contained in the set<br />
		// Post: Object element is not contained in the set and the <br />
//	   cardinality decreases by 1<br />
		void Remove(Object element);<br />
<br />
		// Pre: true<br />
		// Post: return true if Object element is contained in the set; <br />
//	   otherwise, return false.<br />
		bool IsMember(Object element);<br />
<br />
		// Pre: true<br />
		// Post: return true if Cardinality = 0; otherwise, return false.<br />
		bool IsEmpty();<br />
 <br />
		// Pre: true<br />
		// Post: return true if all elements in the set are contained in <br />
//	   set anotherSet; otherwise return false.<br />
		bool IsSubsetOf(ISet anotherSet);<br />
<br />
		// Pre: true<br />
		// Post: return true if all elements in this set are contained in <br />
//	   set anotherSet and all elements in set anotherSet are <br />
//	   also contained in this set; otherwise, return false.<br />
		bool IsEqual(ISet anotherSet);<br />
<br />
		// Pre: true<br />
		// Post: return a set that contains all elements in set <br />
//	   anotherSet and all elements in this set<br />
		ISet Union(ISet anotherSet);<br />
<br />
		// Pre: true<br />
		// Post: return a set that contains elements in both set <br />
// 	   anotherSet and this set<br />
		ISet Intersection(ISet anotherSet);<br />
<br />
		// Pre: true<br />
		// Post: return a set that contains elements that are contained <br />
//	   in this set, but are not contained in set anotherSet<br />
		ISet Difference(ISet anotherSet);<br />
	}<br />
}