Creating Events with C#

Events are defined as variables. When defining an event variable you must assosiate with it a delegate it can use to invoke a target method.

1. Creating the delegate: public delegate void NumberTooHighDelegate(int Number);
2. Creating the event: public event NumberTooHighDelegate NumberTooHighEvent;
3. Raising the event: NumberTooHighEvent(Number1 + Number2);
4. Creating the delegate, creating the event and raising the event should be confined to a given class: public class MTG { private int intA, intB; // note: both delegate and event declarations MUST be made public public delegate void NumberTooHighDelegate(int Number); // public event [Delegate Variable] [Event Variable]; public event NumberTooHighDelegate NumberTooHighEvent; public int AddTwoNumbers(int Number1, int Number2) { if (Number1 + Number2 > 100) NumberTooHighEvent(Number1 + Number2); return Number1 + Number2; } }
5. Assigning an Event Handler to the event outside of the class/object: // this is the event handler method that handles an HtmlInputInput ServerClick event in ASP.NET: private void Add_Click(Object source, EventArgs e) { try { MTG m = new MTG(); // you can use the 'new' keyword to create an instance // of a delegate (virtual method): m.NumberTooHighEvent += new MTG.NumberTooHighDelegate(MTG_NumberTooHigh); txtAns.Value = m.AddTwoNumbers(Convert.ToInt32(txtNum1.Value), Convert.ToInt32(txtNum2.Value)).ToString(); } catch (Exception err) { ltrStatus.Text = err.Message; } } // this is the Delegate method for the MTG.NumberTooHigh event: private void MTG_NumberTooHigh(int Number) { ltrStatus.Text = "The sum of two numbers provided exceeded 100!"; }