Chapter 10: Arrays
Programming with Microsoft Visual Basic
.NET, Second Edition
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
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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
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Arrays
• 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
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Arrays (continued)
• The most commonly used arrays are onedimensional and two-dimensional
• Programmers use arrays to store related data in
the internal memory of the computer
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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
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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
named states
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One-Dimensional Arrays (continued)
• Declaring a one-dimensional array
– Version 1
{Dim | Private} arrayname(highestSubscript) As
datatype
– Version 2
{Dim | Private} arrayname() As datatype =
{initialValues}
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One-Dimensional Arrays (continued)
• Examples of declaring an array
– Dim cities(3) As String
– Private states() As String = {“Hawaii”, “Alaska”,
“Maine”}
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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”
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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
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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
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Displaying the Contents of a OneDimensional 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
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Displaying the Contents of a OneDimensional Array (continued)
Figure 10-6: uiDisplayButton’s Click event procedure
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The For Each…Next Statement
Figure 10-8: Syntax and an example of the For Each…Next
statement
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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
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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
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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
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Calculating the Average Amount
Stored in a One-Dimensional
Numeric Array (continued)
Figure 10-11: uiCalcAvgButton’s Click event procedure
(continued)
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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
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Updating the Values Stored in a OneDimensional Array
• The sales manager at Jillian Company wants a
procedure that:
– Allows her to increase the price of each item the
company sells
– Displays each item’s new price in the
uiNewPricesLabel control
• uiUpdateButton’s Click event procedure performs
these tasks
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Sorting the Data Stored in a OneDimensional 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
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Sorting the Data Stored in a OneDimensional Array (continued)
• 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)
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Using a Module-Level OneDimensional 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
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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
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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
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Parallel One-Dimensional Arrays
(continued)
Figure 10-19: Illustration of a price list stored in two onedimensional arrays
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Structures
• Structure statement: can be used to create your
own data types in Visual Basic .NET
• Data types created using the Structure statement
are referred to as user-defined data types or
structures
• Members included in the structure can be
variables, constants, or procedures
• In most cases, members are variables
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Structures (continued)
Figure 10-21: Syntax and an example of the Structure statement
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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
variable
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Using a Structure to Declare a
Variable (continued)
Figure 10-23: Syntax
and examples of
storing data in a
member variable
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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
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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
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Two-Dimensional Arrays
• A two-dimensional array resembles a table in that
the variables are in rows and columns
Figure 10-32: Illustration of a two-dimensional array
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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
subscripts
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Two-Dimensional Arrays (continued)
Figure 10-34: Syntax versions and examples of declaring a twodimensional array
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Storing Data in a Two-Dimensional
Array
Figure 10-35: Syntax
and examples of
entering data into a twodimensional array
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Searching a Two-Dimensional Array
Figure 10-36: uiDisplayPriceButton’s Click event procedure
using a two-dimensional array
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Searching a Two-Dimensional Array
(continued)
Figure 10-36:
uiDisplayPriceButton’s
Click event procedure
using a twodimensional array
(continued)
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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
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The Tax Calculator Application
(continued)
Figure 10-37: Interface for the Tax Calculator application
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The Tax Calculator Application
(continued)
Figure 10-40: TOE chart for the Tax Calculator application
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Coding the uiCalculateButton Click
Event Procedure
Figure 10-41: Pseudocode for the uiCalculateButton’s Click
event procedure
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Coding the uiCalculateButton Click
Event Procedure (continued)
Figure 10-41: Pseudocode for the uiCalculateButton’s Click
event procedure (continued)
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Summary
• Two versions of the syntax used to declare a
one-dimensional array:
– {Dim | Private} arrayname(highestSubscript) As
datatype
– {Dim | Private} arrayname() As datatype =
{initialValues}
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Summary (continued)
• To refer to a variable in an array, use the array’s
name followed by the variable’s subscript
• To create parallel one-dimensional arrays, create
two one-dimensional arrays
• To create an array of structures, use the
Structure statement to create a record structure,
then use the record structure to declare the array
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Summary (continued)
• Two versions of the syntax used to declare a twodimensional array:
– {Dim | Private} arrayname(highestRowSubscript,
highestColumnSubscript) As datatype
– {Dim | Private} arrayname(,) As datatype =
{{initialValues}, {initialValues},…{initialValues}}
• Syntax used to refer to a variable included in a
two-dimensional array:
arrayname(rowSubscript, columnSubscript)
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