1. CIS16 Application Development and Programming using Visual Basic.net
Chapter 7
String Manipulation and Menus

2. Objectives After studying Lesson A, you should be able to:
Determine the number of characters in a string
Remove characters from a string
Insert characters in a string
Align the characters in a string
Search a string
Access the characters in a string
Compare strings using pattern matching

3. Lesson B Objectives After studying Lesson B, you should be able to:
Include a MenuStrip control on a form
Add elements to a menu
Assign access keys to menu elements
Enable and disable a control
Assign shortcut keys to commonly used menu items
Code a menu item’s Click event procedure
Include the Like operator in a procedure

4. Lesson C Objectives Include the Length property in a procedure
After studying Lesson C, you should be able to:
Include the Length property in a procedure
Include the Substring method in a procedure
Include the Remove method in a procedure
Include the Insert method in a procedure
Include the Contains method in a procedure

5. String Class Applications often need to manipulate string data
There are many scenarios involving string manipulation:
Determine the first character of an inventory part number
Search an address to find a street name
Make sure an address is properly formatted
String
any set of alphanumeric input
key to working with strings is to know what methods are available

6. String methods (cont'd.)

7. Determining the Number of Characters in a String
Length property
Stores the number of characters contained in a string
Syntax: string.Length
Returns an integer value

8. Working with Strings Determining the Number of Characters in a String
Length Property
Contains the number of characters in a string

9. Removing Characters from a String
Trim Method
Removes (trims) any space characters from both the beginning and end of a string
Remove Method
Removes a specified number of characters located anywhere in a string
The computer makes a temporary copy of the string in memory, and then performs the specified removal on the copy
The original string is not changed
The modified copy is returned to the program

10. Removing Characters from a String (cont'd.)

11. Removing Characters from a String (cont.)
The Product ID Application
Figure 8-7 Sample run of the Product ID application

12. Inserting Characters in a String
Insert method
Inserts characters anywhere in a string
The computer makes a temporary copy of a string and inserts specified characters into the copy
Returns a string with the appropriate characters inserted
startIndex argument
An integer specifying the starting location to insert the value
Represents the position in a string
To insert the value at the beginning of a string, use a startIndex of 0

13. Inserting Characters into a String
Insert Method
Allows you to insert characters anywhere in a string

14. Inserting Characters in a String (cont.)
Aligning the Characters in a String
PadLeft method
Inserts zero or more characters at the beginning of a string
Results in a string of a specified length
Right-aligns the characters within the string
PadRight method
Inserts characters at the end of the string
Left-aligns the characters within the string

15. Searching a String (cont'd.)
Contains Method
Returns the Boolean value True when the subString is contained anywhere in the string
IndexOf Method
Returns an integer: either –1 or a number that is greater than or equal to 0
The –1 indicates that the subString is not contained in the string
A number other than –1 is the character index of the subString’s starting position in the string

16. Inserting Characters in a String (cont.)
Aligning the Characters in a String (cont.)

17. Searching a String Contains method
Used to search a string to find a specific sequence of characters
Returns a Boolean value
True if found
False otherwise
You must specify the characters you are searching for
The search begins with the first character in the string

18. Searching a String (cont.)
IndexOf method
Determines if a string contains a character sequence
Returns an integer specifying the start position of a found character sequence (substring)
If the substring is not found, the method returns -1
You must specify the sequence of characters to search for
You may specify the index of the character at which to begin the search
If not specified, the search begins with the first character in the string

19. Searching a String

20. Searching a String (cont'd.)

21. Searching a String (cont.)
The City and State Application
Allows the user to enter a string
Composed of a city name, a comma, a space, and a state name
Displays index of the comma in the string

22. Accessing the Characters in a String
Substring method
Used to access any number of characters in a string
Returns a string with a specified number of characters
Specify the index of the first character to access in the string, and the number of characters to retrieve
If the number of characters is not specified, the method returns all characters from the startIndex position to the end of the string

23. Accessing the Characters in a String
Substring Method
Accesses any number of characters in a string

24. Accessing the Characters in a String (cont.)
The Rearrange Name Application
Allows the user to enter a first name, a space, and a last name
Displays the name as last name, comma, space, first name

25. Accessing the Characters in a String (cont.)
The Rearrange Name Application (cont.)
Figure 8-17 Interface showing the rearranged name
Figure 8-16 btnRearrange_Click procedure

26. Using Pattern-Matching to Compare Strings
Like operator
Allows the use of pattern-matching characters to determine whether one string is equal to another
You must specify the string to be examined and the pattern to be matched
The pattern can contain pattern-matching characters
Returns a Boolean value
True if a match is made
False otherwise

27. Using Pattern Matching to Compare Strings
Like Operator
Allows you to use pattern-matching characters to determine whether one string is equal to another string

28. Using Pattern Matching to Compare Strings (cont'd.)

29. Using Pattern Matching to Compare Strings (cont'd.)

30. Using Pattern Matching to Compare Strings (cont'd.)

31. Random Numbers Random numbers are used in many computer game programs.
The numbers can be integers or real numbers, which are numbers with a decimal place.
Most programming languages provide a pseudo-random number generator
is a mathematical algorithm that produces a sequence of numbers.
numbers are not completely random, they are sufficiently random for practical purposes.

32. Random Class Random class must be instantiated to use its methods
Methods allowing you to retrieve the next number produced by the random number generator:
NextDouble() method returns a double random number between 0.0 and 1.0
Next() method returns an integer random number between two integer values
NextBytes() method fills the elements of a specified array of bytes with random numbers.
Syntax:
dim objRnd as new Random

33. Seeding the random number generator
Obtain random value when instantiated
dim objRnd as new Random(50)
Obtain random value using the method
objRnd.Next()
objRnd.Next(50,100)
objRnd.Next(2000)

34. Code example – generates a number between 1 and 10
dim objRnd as new Random Dim intRandomNum as Integer intRandomNum = objRnd.next(1,11)