Clearly Visual Basic: Programming with Visual Basic 2008 Chapter 24 The String Section.

Clearly Visual Basic: Programming with Visual Basic 2008

Chapter 24 The String Section


Objectives

• Determine the number of characters in a string

• Remove spaces from the beginning and end of a string

• Replace characters in a string

• Insert characters in a string

• Search a string

• Access characters in a string

• Compare strings using pattern-matching

2


Working with Strings

• Many times:– An application will need to manipulate (process)

string data in some way

• The first string manipulation technique in this chapter– Shows you how to determine the number of

characters in a string

3


How Many Characters Are There?

• If an application expects the user to enter a seven-digit phone number: – Application’s code should verify that the user entered

the required number of characters

• Number of characters contained in a string– Stored in the string’s Length property

• Value stored in the property is an integer

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Clearly Visual Basic: Programming with Visual Basic 2008 5


Get Rid of Those Spaces

• Trim method– Used to remove (trim) any spaces from both the

beginning and end of a string– Does not remove any characters from the original

string– Returns a string that excludes any leading or trailing

spaces

6


The Product ID Application

• Displays (in a label control): – A listing of the product IDs entered by the user

• Each product ID must contain exactly five characters

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Let’s Make a Substitution

• Replace method – Used to replace a sequence of characters in a string

with another sequence of character

• Figure 24-4 – oldValue

• The sequence of characters that you want to replace in the string

– newValue • The replacement characters

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I Need To Fit This in Somewhere

• Insert method– Used to insert characters– Examples

• Insert an employee’s middle initial within his or her name

• Insert parentheses around the area code in a phone number

11


The Phone Numbers Application

• Saves (in a sequential access file):– The phone numbers entered by the user

• Each phone number is entered using: – 12 characters in the following format: 111-222-3333

• Before writing a phone number to the file:– The application removes the hyphens and then

verifies that the phone number contains 10 characters

• Figures 24-8 and 24-9– Show code and resulting display for formatted

numbers

13


Where Does it Begin?

• IndexOf method – Used to search a string to determine whether it

contains a specific sequence of characters– Example

• Determining whether the area code “(312)” appears in a phone number

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I Just Want a Part of It

• Substring method – Used to access any number of characters contained

in a string

• Figure 24-11 – startIndex

• The index of the first character you want to access in the string

– count argument • Specifies the number of characters you want to

access

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The Rearrange Name Application

• User interface – Provides a text box for entering a person’s first name

followed by a space and the person’s last name

• Application– Rearranges name so that the last name comes first,

followed by a comma, a space, and the first name

• Figure 24-12– Shows code to display rearranged name

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I Like This Operator

• Like operator – Allows you to use pattern-matching characters to

determine whether one string is equal to another

• Figure 24-14 – In the syntax, both string and pattern must be String

expressions• However, pattern can contain one or more of the

pattern-matching characters listed in the figure

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Modifying the Product ID Application

• Ensure that the five characters in the product ID are three letters followed by two numbers

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Summary

• String’s Length property – Stores an integer that represents the number of

characters contained in the string

• Visual Basic – Provides methods that allow you to manipulate

strings

• First character in a string has an index of 0

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Clearly Visual Basic: Programming with Visual Basic 2008 Chapter 24 The String Section.

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