Visual basic dot NET arrays

One-Dimensional Arrays continued• You refer to each variable in an array by its name and the variable’s subscript Figure 10-3: Names of the variables in a one-dimensional array... Manipu

Visual basic Net Arrays

Using a One-Dimensional Array

Lesson A Objectives

• Declare and initialize a one-dimensional array

• Store data in a one-dimensional array

• Display the contents of a one-dimensional array

• Code a loop using the For Each…Next statement

• Access an element in a one-dimensional array

Using a One-Dimensional Array

Lesson A Objectives (continued)

• Search a one-dimensional array

• Compute the average of a one-dimensional

array’s contents

• Find the highest entry in a one-dimensional array

• Update the contents of a one-dimensional array

• Sort a one-dimensional array

• A simple or scalar variable is one that is

unrelated to any other variable in memory

• An array is a group of variables that have the

same name and data type and are related in

some way

Arrays (continued)

• The most commonly used arrays are

one-dimensional and two-one-dimensional

• Programmers use arrays to store related data in the internal memory of the computer

One-Dimensional Arrays

• A one-dimensional array is simply a row (or

column) of variables

• Each element in an array is identified by a

subscript, which Visual Basic NET assigns to the variable when the array is created

One-Dimensional Arrays (continued)

• You refer to each variable in an array by its name and the variable’s subscript

Figure 10-3: Names of the variables in a one-dimensional array

One-Dimensional Arrays (continued)

• Declaring a one-dimensional array

One-Dimensional Arrays (continued)

• Examples of declaring an array

– Dim cities(3) As String

– Private states() As String = {“Hawaii”, “Alaska”,

“Maine”}

Storing Data in a One-Dimensional

Array

• In most cases, you use an assignment statement

to enter data into an existing array

• Syntax: arrayname(subscript) = value

• Examples

– cities(0) = “Madrid”

– cities(1) = “Paris”

– cities(2) = “Rome”

Manipulating One-Dimensional

Arrays

• You will learn how to perform the following tasks using a one-dimensional array:

– Display the contents of an array

– Access an array element using its subscript

– Search the array

– Calculate the average of the data stored in a

numeric array

Manipulating One-Dimensional

Arrays (continued)

• You will learn how to perform the following tasks using a one-dimensional array (continued):

– Find the highest value stored in an array

– Update the array elements

– Sort the array elements

Displaying the Contents of a

One-Dimensional Array

• uiDisplayButton’s Click event procedure

– Demonstrates how you can display the contents of

an array in a label control

– Uses the For…Next statement to display each

array element

– You also could use the Do…Loop statement or the For Each…Next statement

Displaying the Contents of a Dimensional Array (continued)

One-Figure 10-6: uiDisplayButton’s Click event procedure

The For Each…Next Statement

Using the Subscript to Access an Element in a One-Dimensional Array

• XYZ Corporation pays its managers based on six different salary codes, 1 through 6

• Each code corresponds to a different salary

• uiSalaryButton’s Click event procedure displays the salary corresponding to the code entered by the user

Searching a One-Dimensional Array

• The sales manager at Jacobsen Motors wants a procedure that allows him to determine the

number of salespeople selling above a certain

amount, which he will enter

• uiSearchButton’s Click event procedure searches the array, looking for values that are greater than the amount entered by the sales manager

Calculating the Average Amount Stored in a One-Dimensional

Numeric Array

• uiCalcAvgButton’s Click event procedure

calculates and displays the average test score

Figure 10-11: uiCalcAvgButton’s Click event procedure

Calculating the Average Amount Stored in a One-Dimensional Numeric Array (continued)

Determining the Highest Value

Stored in a One-Dimensional Array

• Sharon Johnson wants a procedure that displays the highest amount she has earned in a week

• uiHighestButton’s Click event procedure will

search the array, looking for the highest amount

Updating the Values Stored in a

Sorting the Data Stored in a

One-Dimensional Array

• Arranging data in a specific order is called sorting

• Array.Sort method

– Can be used to sort the elements in a

one-dimensional array in ascending order

– Syntax: Array.Sort(arrayname)

• uiSortButton’s Click event procedure uses the

Array.Sort method to sort the numbers array in ascending order

Sorting the Data Stored in a Dimensional Array (continued)

One-• To sort a one-dimensional array in descending order:

– Use Array.Sort to sort the array in ascending order – Use Array.Reverse to reverse the array elements

• Syntax of the Array.Reverse method:

Array.Reverse(arrayname)

Using a Module-Level

One-Dimensional Array

• Names application

– Needs to display the names contained in a

sequential access file

– Should give the user the choice of displaying the names in either ascending or descending order

• The names array is declared in the form’s

Declarations section, making it a module-level

array

More on One-Dimensional Arrays

Lesson B Objectives

• Create and manipulate parallel one-dimensional arrays

• Create a structure

• Declare a structure variable

• Create and manipulate a one-dimensional array

of structures

Parallel One-Dimensional Arrays

• Arrays that are related by an element’s position (subscript)

• Searching one array gives you the subscript for the other array

• To store a price list, which includes a string and a number, you can use two one-dimensional arrays

– A String array to store the product IDs

– An Integer array to store the prices

Parallel One-Dimensional Arrays

(continued)

Figure 10-19: Illustration of a price list stored in two

• Members included in the structure can be

variables, constants, or procedures

• In most cases, members are variables

Structures (continued)

Using a Structure to Declare a

Variable

• Variables declared using a structure are often

referred to as structure variables

Figure 10-22: Syntax and an example of declaring a structure

Using a Structure to Declare a

Variable (continued)

Figure 10-23: Syntax

and examples of

Creating an Array of Structure

Variables

• Assigning initial values to an array is referred to

as populating the array

• Refer to a member variable in an array element using the syntax:

arrayname(subscript).memberVariableName

Using a Two-Dimensional Array

Lesson C Objectives

• Create and initialize a two-dimensional array

• Store data in a two-dimensional array

• Search a two-dimensional array

Two-Dimensional Arrays (continued)

• Each variable (element) in a two-dimensional

array is identified by a unique combination of two subscripts

• The subscripts specify the variable’s row and

column position in the array

• Refer to each variable in a two-dimensional array

by the array’s name and the row and column

Two-Dimensional Arrays (continued)

Figure 10-34: Syntax versions and examples of declaring a

two-Storing Data in a Two-Dimensional

Array

Figure 10-35: Syntax

and examples of

Searching a Two-Dimensional Array

Figure 10-36: uiDisplayPriceButton’s Click event procedure

Searching a Two-Dimensional Array

The Tax Calculator Application

• John Blackfeather, the owner and manager of the Perrytown Gift Shop, should be able to use the application to calculate the weekly federal

withholding tax for his employees

• To calculate the federal withholding tax, the user would need to enter the taxable wages in the

Taxable wages text box and then click the

Calculate Tax button

The Tax Calculator Application

(continued)

The Tax Calculator Application

(continued)

Figure 10-40: TOE chart for the Tax Calculator application

Coding the uiCalculateButton Click

Event Procedure

Coding the uiCalculateButton Click

Event Procedure (continued)

Figure 10-41: Pseudocode for the uiCalculateButton’s Click

• To create an array of structures, use the

Structure statement to create a record structure, then use the record structure to declare the array