microsoft visual basic 2015 chapter 04

► Create, modify, and program a TextBox object► Use code to place data in the Text property of a Label object ► Use the AcceptButton and CancelButton properties ► Understand and declare

Microsoft Visual Basic 2015

CHAPTER FOUR

Variables and

Arithmetic Operations

► Create, modify, and program a TextBox object

► Use code to place data in the Text property of a Label object

► Use the AcceptButton and CancelButton properties

► Understand and declare String and Numeric variables

►Use assignment statements to place data in variables

► Use literals and constants in coding statements

► Understand scope rules for variables

► Convert string and numeric data

►Understand and use arithmetic operators and arithmetic operations

► Format and display numeric data as a string

► Create a form load event

► Create a concatenated string

►Debug a program

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Sizing and Positioning a TextBox Object

► Select the TextBox object Select the (Name) property and type the desired name Scroll in the Properties window until the Text property is visible and then tap or click the right column for the Text property

► Type the maximum number of characters the user normally will enter into the text box and then press the ENTER key Programmers often use the digit 8 in this situation because it is wider than other digits

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Sizing and Positioning a TextBox Object

► Using the Properties window, change the Font property to the correct font and font size Then, drag the right edge of the TextBox object and resize it to be slightly wider than the entry

► To horizontally align the text in the label and the text in the text box, drag the text box

up until a red snap line indicates the bottoms of the text are aligned Then, release the left mouse button

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Sizing and Positioning a TextBox Object

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Aligning Text in a TextBox Object

► Select the TextBox object In the Properties window, scroll until the TextAlign property is visible, tap

or click the TextAlign property in the left column, and then tap or click the list arrow in the right column of the TextAlign property

► Tap or click the desired alignment option in the TextAlign property list

► Because the TextBox object is sized properly, remove the digits in the TextBox object Select the characters in the Text property, press the DELETE key on your keyboard, and then press the

ENTER key

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Aligning Text in a TextBox Object

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Creating a MultiLine Text Box

► Select the TextBox object, tap or click the Action tag, and then point to the MultiLine check box

►Tap or click the MultiLine check box

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Creating a MaskedTextBox Object

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Creating a MaskedTextBox Object

► Drag a MaskedTextBox NET component from the Toolbox to the Windows Form

object Then, tap or click the Action tag on the TextBox object and point to the Set

Mask command

► Tap or click Set Mask on the MaskedTextBox Tasks list and then tap or click the

desired mask description in the Input Mask dialog box

► Tap or click the OK button in the Input Mask dialog box and then tap or click anywhere

in the Windows Form object

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Creating a MaskedTextBox Object

►Drag the Label object up until the red snap line appears Then release the Label object

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Accept Button in Form Properties

► After the Button objects are added, tap or click a blank area in the Windows Form object to select it Scroll in the Properties window until the AcceptButton property is visible Tap or click the AcceptButton property name in the left column and then tap or click the AcceptButton property list arrow in the right column

►Tap or click the desired button in the AcceptButton property list

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Accept Button in Form Properties

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Cancel Button in Form Properties

► When the user presses the esc key, the event handler processing will be executed for the button identified as the Cancel button

► Tap or click a blank area in the Windows Form object to select it

► Tap or click the CancelButton property name in the left column in the Properties

window for the Windows Form object, and then tap or click the CancelButton list arrow

►Tap or click the desired button name in the CancelButton property list

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Visual Studio Preparation for Code Entry

►With the Toolbox visible, tap or click the Toolbox Close button The Toolbox closes and the work area expands in size To display the Toolbox after it has been closed, tap or click the View menu and then tap or click Toolbox

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String Data Type

► A String data type can store any character available on the computer

► The data type for the value the user enters in a TextBox object and that is stored in the Text property

of the TextBox object is string

► A variable is a named location in RAM where data is stored

► A String variable is a named location in RAM that can store a string value

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String Data Type

► Press the SPACEBAR, type the word As, and then press the SPACEBAR again

► Because the entry should be String, type str

►Press the ENTER key

► Press the SPACEBAR, press the EQUAL SIGN key, and then press the SPACEBAR

► Type the name of the text box containing the value you wish to use

► Press the PERIOD key and then, if necessary, type te to highlight the Text entry in the IntelliSense list

► Press the ENTER key

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Numeric Data Types

►A numeric data type must be used in arithmetic operations

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Numeric Data Types

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Other Data Types

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Other Data Types

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Miscellaneous Data Types

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Forced Literal Types

►Sometimes you might want a literal to be a different data type than the Visual Basic default type

► The declaration of a constant begins with the letters Const, not the letters Dim

► You must assign the value to be contained in the constant on the same line as its definition

► You cannot attempt to change the value of the constant anywhere in the program If you do, you will produce a compiler error

► The letter c often is placed before the constant name to identify it throughout the program as a variable that cannot be changed

► Other than the letter c, constant names are formed using the same rules and techniques as other variable names

► The scope of a variable specifies where the variable can be referenced in a Visual Basic statement

within the program

► You declare a variable in the region within a program

► The code between the Sub statement and the End Sub statement is a procedure

► A variable that can only be referenced within the region of the program where it is defined is called a

local variable

• Local variables have a certain lifetime in the program

► Global variables can be used in multiple regions of a Visual Basic program

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Converting Variable Data

► Visual Basic includes several procedures that allow you to convert one data type to another data type

► A procedure to convert a String data type to an Integer data type is named ToInt32

►The procedure is in the Convert class, which is available in a Visual Studio 2015 class library

► A procedure that returns a value is called a Function procedure, or a function

► An argument identifies a value required by a procedure

►Every procedure is part of a class

► To prevent automatic conversion of values, the developer must insert the Option Strict On statement in the program prior to any event handler code

► The Option Strict On statement explicitly prevents any default data type conversions that would cause data loss and prevents any conversion between numeric types and strings

• Exponentiation (^) is performed first

• Multiplication (*) and division (/) are performed next

• Integer division (\) is next

• MOD then occurs

• Addition (+) and subtraction (-) are performed last

• Within these five steps, calculations are performed left to right

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Displaying Numeric Output Data

► Use the format specifier to identify the format for the numeric data to be returned by

the ToString function

► The precision specifier is a number included within the quotation marks in the

function call that identifies the number of positions that should be returned to the right

of the decimal point

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Clearing the Text Property of a Label

► The Clear procedure cannot be used with a Label object

►You must write an assignment statement that assigns a null length string to the Text property

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Setting the Focus

►When the focus is on a TextBox object, the insertion point is located in the text box

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Form Load Event

►A form load event occurs when the program starts and Windows Form Object is loaded into computer memory

► The process of joining two different values into a single string is called concatenation

►The values being concatenated must be String data types

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Debugging Your Program

► A Format Exception occurs when the

user enters data that a statement

within the program cannot process

properly

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Debugging Your Program

► An Overflow Exception occurs when the user enters a value greater than the

maximum value the statement can process

► It is not possible to divide by zero, so if your program contains a division operation

and the divisor is zero, the Divide By Zero Exception will occur

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Event Planning Document

► Create, modify, and program a TextBox object

► Use code to place data in the Text property of a Label object

► Use the AcceptButton and CancelButton properties

► Understand and declare String and Numeric variables

►Use assignment statements to place data in variables

► Use literals and constants in coding statements

► Understand scope rules for variables

► Convert string and numeric data

►Understand and use arithmetic operators and arithmetic operations

► Format and display numeric data as a string

► Create a form load event

► Create a concatenated string

►Debug a program

Microsoft Visual Basic 2015

CHAPTER FOUR COMPLETE

Variables and

Arithmetic Operations