This document discusses different GUI events in C# .NET including button click events, mouse down events, key down events, and leave events. It explains that an event is triggered when something special happens in the user interface, and event handlers contain code that is executed when those events are raised. It provides examples of writing event handler methods for the click of a button, mouse down on a form, key presses, and leaving a textbox. The event handler methods are linked to the events automatically in the Visual Studio IDE.

1. Chapter 10C# .NET Events

2. Button Click eventMouse Down eventKey Down eventLeave eventWhat will we be learning?

3. An Event is when something special happensInbuilt code gets activated when the Event happenedThe Event is then said to be “handled”GUI Events such as when a button is clicked, when the mouse right click and moreEvent

4. An event can be a mouse click, a keystroke or an alarmA class that raised the event is known as "event sender"A method used to handle a particular event is known as "event handler"In Visual Studio IDE, the mechanism is done automatically

5. private void button1_Click(object sender, EventArgs e){ ….}Part 1 – The Click Event for Button

6. private void button1_Click(object sender, EventArgs e){ ….}Part 1 – The Click Event for ButtonWho is calling this method:in this case, it is button1

7. private void button1_Click(object sender, EventArgs e){ ….}Part 1 – The Click Event for ButtonWhat event is it?:in the next example, we shall use the event arguments to check if it is left or right mouse click

8. VS IDE link the method as the event handler automaticallyE.g. in Form1.Designer.csPart 1 – The Click Event for Button

9. New solution with project: SpfChapter10_eventsAdd a new button, change text to "Quit"Add codesTo exit/quit an application

10. Design ViewSelect Form1Part 2 – Mouse Down

11. View Properties windowSelect the lightning bolt (events)Part 2 – Mouse Down

12. Double click on "MouseDown" eventPart 2 – Mouse Down

13. We want to handle the event when a mouse click down on the formDouble click on "MouseDown" eventPart 2 – Mouse Down

14. e.MouseEventArgs e (Extra)Left or Right buttonNumber of clicksX, Y: position of mouse

15. Design view, Select Form1In Properties window, view eventsWe want to handle when a key is pressedDouble click on "KeyDown" eventPart 3 – Key Down

16. e.KeyEventArgs e (Extra)Alt key is pressedCtrl key is pressedData about the key pressedShft key is pressed

17. Design view, Add a new textboxIn Properties window, view eventsWe want to handle after user key in some text and leaving the textboxPart 4 – Leave event

18. Double click on "Leave" eventPart 4 – Leave event

19. The TabIndex property refers to which control will be selected when the Tab key is pressedThe TabIndex allows you to set the Tab order for all the controls on your form TabIndex

20. Button Click eventMouse Down eventKey Down eventLeave eventSummary