Chapter 1 : Introduction to Visual Programming

Question 1

What components respond to actions from users such as mouse clicks, pressing keys on keyboards or placing the mouse cursor over user interface objects

Answer 1

1. Graphical User Interface ( GUI )

Question 2

What are the actions known as ? ( mouse click, pressing key on keyboards )

Answer 2

1. Event

Question 3

What does a Visual C# applications project start with? ( 3 )

Answer 3

1. Designer
2. Toolbox
3. Property Window

• An empty form is generated and its name is Form1

Question 4

What is the form basic width and height

Answer 4

1. 300 pixel each

Question 5

What does the property window do?

Answer 5

1. Change the settings for the appearance and other characteristics of a GUI object

Question 6

What will be displayed in the column’s property list? ( 2 )

Answer 6

1. Left Column
   
   • Property’s Name
2. Right Column
   
   • Property’s Value

Question 7

What is controls name

Answer 7

1. Identifiers of the controls

Question 8

List out the rules for naming controls

Answer 8

1. The first character must be letter ( lower , uppercase doesn’t matter ) or an underscore
2. All other characters can be alphanumerical characters or underscores
3. The name cannot contain spaces

• Example
  showDayButton
  DisplayTotal
  _ScoreLabel

Question 9

List out 3 ways for how C# code is primarily organized?

Answer 9

1. Namespace
   
   • A container that holds classes
2. Class
   
   • A container that holds methods
3. Method
   
   • Group of one or more programming statements that perform some operations

Question 10

What is a file that containes program code is called?

Answer 10

1. Source Code File

Question 11

What source code file that is automatically created when creating a new project?

Answer 11

1. Program.cs
   
   • Contains the application’s start-up code to be executed when the application runs
2. Form1.cs
   
   • Contains code that is associated with the Form1 form

• Can open through Solution Explorer

Question 12

How does C# code is organized?

Answer 12

1. As methods

Question 13

What does a program waits in event-driven programming?

Answer 13

1. An event to occur after executed
2. Determine how controls ( button, textbox ) respond to events that are set for the respective control

Question 14

Who controls the program response in event-driven programming?

Answer 14

1. User

Question 15

List out 3 ways that the event can occur

Answer 15

1. The user doing something ( Click a button )
2. Something happening within th ecomputer ( System Shutdown )
3. Something happening within the program ( Program Crash )

Question 16

List out 5 types of events

Answer 16

1. Activate Events
   
   • User selects item on screen
2. Changed Events
   
   • Control property modified
3. Focus Events
   
   • Control gets or loses focus
4. Key Events
   
   • User interacts with keyboard
5. Mouse Events
   
   • User interacts using mouse

Question 17

What is an event handler? ( 2 )

Answer 17

1. Method that executes when a specific takes place
2. Code segment similar to the following will be created automatically

private void myButton_Click(object sender, EventArgs e)
{
}

Question 18

What does a message box does?

Answer 18

1. Displays a message

Question 19

What is the code for showing a message box?

Answer 19

1. MessageBox.Show(“Hello”)

• Placing it inside the event handler ( button ) can display the string in the message box when the button is clicked

Question 20

What does a label do?

Answer 20

1. Display text on a form and can be used to display unchanging text or program output

Question 21

List out 6 commonly used properties

Answer 21

1. Text ( Displayed text )
2. Name ( Method name )
3. Font
4. BorderStyle
5. AutoSize
6. TextAlign

Question 22

List out 9 values that the TextAlign property supports

Answer 22

1. TopLeft
2. TopCenter
3. TopRight
4. MiddleLeft
5. MiddleCenter
6. MiddleRight
7. BottomLeft
8. BottomCenter
9. BottomRight

• Select by clicking the dropdown button in TextAlign property

Question 23

How to change a property ( Change label text from “Hi” to “Hello” ) ?

Answer 23

1. Use Assignment Operator ( = )

label1.Text = “Hello”;

• Details
  1. Control name followed by a dot
  2. Property to be modified ( left side , .Text )
  3. Value to be assigned ( Right side , = “Hello” )

Question 24

How to change the color properties?

Answer 24

1. Using class name Color followed by a dot

label1.BackColor = Color.blue

Question 25

How to use concatenation?

Answer 25

1. With the + operator

label1.Text = “Welcome ” + “ to C#”;

Question 26

What is the difference when the concatenation operator ( + ) is used in
1. int , double
2. string

Answer 26

1. Arithmetic ( Add )
2. Concatenate ( Join String )

Question 27

How to change the form properties?

Answer 27

1. Using this keyword

private void button1_Click(object sender, EventArgs e)
{
this.BackColor = Color.Red ;
}

• When the button1 is clicked, the background color will be changed to Red

Question 28

What does IntelliSense does?

Answer 28

1. Provides automatic code completion as I write programming statements

• Access through Ctrl + .
• Provides an array of options that make language reference easily accessible

Question 29

List out C# comments for :
1. Single Line Comment
2. Multiline Comment

Answer 29

1. //
   
   • // This is single line
2. /**/
   
   • /*
     This is
     multiline comment
     */

Question 30

Why does programmes frequently use blank lines and indentation in their codes?

Answer 30

1. To make code more human-readable

Question 31

What code should I add when I want to close an application’s form in code?

Answer 31

1. this.Close()

• it is commonly used in an Exit button
  private void exitButton_Click(object sender, EventArgs e)
  {
  // Close the form.
  this.Close();
  }

Question 32

What causes syntax errors?

Answer 32

1. Misspelled words and missing punctuation

Question 33

How would IDE perform to when having Syntax Errors?

Answer 33

1. Normally trapped by IDE as they are typed

• Explanation shown when cursor held over error
• Should be corrected before running program

Question 34

What would compiler do when having syntax errors

Answer 34

1. Uncorrected syntax errors
   
   • Message box prompts user to continue
   • Error list window displays compilation errors

MessageBox.Show(“Bye)

Question 35

What underline style when a syntax error is found?

Answer 35

1. Jagged line

Question 36

Why Run-time errors occured?

Answer 36

1. Invalid calculation
2. Attempt to open a non-existent file

Question 37

When does Run-time errors occured?

Answer 37

1. Only apparent when program runs

Question 38

What will be displayed when run-time errors occured?

Answer 38

1. IDE displays a message box
   
   • Nature of error
   • Approximate location of error ( line number )