1.

Objectives Determine the number of characters contained in a string
Remove characters from a string Determine whether a string begins or ends with one or more specific characters Access characters in a string Insert characters in a string Search a string for one or more characters Compare strings using the Like operator Microsoft Visual Basic .NET: Reloaded

Manipulating Stings in Visual Basic .NET
Applications often need to manipulate (process) strings Verify part number begins with a specific letter Determine whether last 3 characters of employee number are valid Start by determining number of characters contained in a string Microsoft Visual Basic .NET: Reloaded

Determining the Number of Characters Contained in a String
Microsoft Visual Basic .NET: Reloaded

Removing Characters from a String

The Remove Method Removes characters from anywhere in the string
Uses characters index which indicates a character’s position in string startIndex, count determine starting position and number of characters to remove respectively startIndex is zero based to remove the first character, it must have a value of 0 Microsoft Visual Basic .NET: Reloaded

HOW TO… Microsoft Visual Basic .NET: Reloaded

Determining Whether a String Begins or Ends with a Specific Sequence of Characters
Use StartsWith method to determine whether a specific sequence of characters (substring) occurs at beginning of string Returns true if substring at beginning, false otherwise Use EndsWith method to determine whether a specific sequence of characters (substring) occurs at ending of string Returns true if substring at ending, false otherwise Microsoft Visual Basic .NET: Reloaded

HOW TO…(continued) Microsoft Visual Basic .NET: Reloaded

Accessing Characters Contained in a String
Use Substring method Method has two arguments startIndex argument refers to index of the first character you want to access count argument refers to number of characters to access count argument is optional Microsoft Visual Basic .NET: Reloaded

Replacing Characters in a String
Use Replace method Replaces a sequence of characters with another sequence of characters Contains two arguments oldValue argument is the sequence to be removed newValue argument is the sequence of characters to be inserted Replaces all occurrences of oldValue with newValue in the string Microsoft Visual Basic .NET: Reloaded

Mid Statement Replaces a specified number of characters in a string with characters from another string targetString - string in which you want characters replaced start - character position of the first character you want replaced count - specifies the number of characters to replace and is optional replacementString - contains the replacement characters Microsoft Visual Basic .NET: Reloaded

Inserting Characters at the Beginning and End of a String
PadLeft method pads string on the left, inserting characters at the beginning PadRight method pads string on the right, inserting characters at the end of the string length argument is the desired length of the string (total number of characters including inserted characters) character argument is optional and specifies the character you want to pad with If blank, the space character is used Microsoft Visual Basic .NET: Reloaded

Inserting Characters within a String
Insert Method inserts a character or characters in a string at a specified location startIndex argument specifies where you want the value to be inserted value argument is the character of characters you want to insert Microsoft Visual Basic .NET: Reloaded

Searching a String IndexOf method searches a string for a specific sequence of characters and returns the beginning position if found or a -1 if not found value argument - specific sequence to search for startIndex argument is optional and is the starting position to begin search Microsoft Visual Basic .NET: Reloaded

The Like Operator Uses pattern-matching characters to determine whether one string is equal to another string Pattern-matching characters specify zero or more characters that fit a specific pattern or character type You can specify a charlist which is a list of characters that can occur in the pattern Use Like operator in an expression to return true if a match occurs, false otherwise Microsoft Visual Basic .NET: Reloaded

Summary of String Manipulation

Programming Example – Hangman’s Game
Application simulates a simplified version of the Hangman game with the following rules: Words have 5 letters Word is initially represented by 5 dashes An attempt is made to guess a letter and, if correct, the dash is replaced with the letter When all dashes have been replaced, the game is over or, when 10 incorrect guesses have occurred (whichever occurs first) Microsoft Visual Basic .NET: Reloaded

TOE Chart Microsoft Visual Basic .NET: Reloaded

User Interface Microsoft Visual Basic .NET: Reloaded

Objects, Properties, and Settings

Tab Order Microsoft Visual Basic .NET: Reloaded

Psuedocode btnExit Click event procedure close the application
btnPlay Click event procedure get a 5-letter word from player 1 repeat while the word does not contain 5 letters get a 5-letter word from the user end repeat convert word to upper case display five dashes in the lblWord control clear the lblIncorrectGuesses control repeat while the came is not over get a letter from player 2, convert the letter to uppercase (continued on next slide) Microsoft Visual Basic .NET: Reloaded

Psuedocode (continued)
repeat for each character in the word if the current character is equal to the letter entered by player 2 replace the appropriate dash in the lblWord control set the blnDashReplaced variable to true end if end repeat If a dash was replaced in the lblWord control if the lblWord control does not contain any dashes set the blnGameOver variable to True display the “Great Guessing!” message in a message box else reset the blnDashReplaced variable to False (continued on next slide) Microsoft Visual Basic .NET: Reloaded

Psuedocode (continued)
else add 1 to the intIncorrectGuesses counter variable display the intIncorrectGuesses value in lblIncorrectGuesses if the user made 10 incorrect guesses set the blnGameOver variable to True display the “Game Over” message in lblWord control display the “Sorry, the word is” message and the word in a message box end if endif end repeat Microsoft Visual Basic .NET: Reloaded

Code Microsoft Visual Basic .NET: Reloaded

Code (continued) Microsoft Visual Basic .NET: Reloaded

Summary Use the Length property to determine number of characters in a string TrimStart and TrimEnd methods respectively removes characters from beginning or end of strings Use Remove method to remove characters anywhere in the string StartsWith method determines whether a string begins with a specific sequence of characters Microsoft Visual Basic .NET: Reloaded

Summary (continued) EndsWith method determines whether a string ends with a specific sequence of characters Substring method accesses one or more characters contained in a string Replace method replaces all occurrences of a given sequence of characters with another sequence of characters Mid statement replaces a specific number of characters with characters from another string Microsoft Visual Basic .NET: Reloaded

Summary (continued) PadLeft allows (padding) insertion of characters at beginning of string. PadRight allows (padding) insertion of characters at end of string Insert method inserts characters within a string and returns string with characters inserted IndexOf method searches for a specific sequence of characters and returns the index of the starting character in the sequence or a – 1 if not found Microsoft Visual Basic .NET: Reloaded

Summary (continued) Like comparison operator allows you to use pattern-matching characters to determine whether one string is equal to another string Microsoft Visual Basic .NET: Reloaded

1.

Similar presentations

Presentation on theme: "1."— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

1.

Similar presentations

Presentation on theme: "1."— Presentation transcript:

Similar presentations

About project

Feedback