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Visual Basic 2005Visual Basic 2005III. STRINGS, CHARACTERS AND REGULAR
EXPRESSIONS
MELJUN CORTESMELJUN CORTES
Strings, Characters and Regular Strings, Characters and Regular ExpressionsExpressionsObjectives
In this chapter you will learn:•To create and manipulate immutable character String objects of class String.•To create and manipulate mutable character String objects of class StringBuilder.•To manipulate character objects of structure Char.•To use regular expressions in conjunction with classes Regex and Match.
Visual Basic 2005
2STRINGS, CHARACTERS AND REGULAR EXPRESSIONS
Fundamentals of Characters and Fundamentals of Characters and StringsStrings
Characters are the fundamental building blocks of Visual Basic source code
Every program is composed of characters that, when grouped together meaningfully, create a sequence that the compiler interprets as instructions
a program also can contain character literals, also called character constants
A character literal is a character that is represented internally as an integer value, called a character code
Visual Basic 2005
Strings, Characters and Regular Expressions
3STRINGS, CHARACTERS AND REGULAR EXPRESSIONS
Fundamentals of Characters and Fundamentals of Characters and StringsStrings
Character literals are established according to the Unicode character set
A string is a series of characters treated as a single unit
A string is an object of class String in the System namespace
Visual Basic 2005
Strings, Characters and Regular Expressions
4STRINGS, CHARACTERS AND REGULAR EXPRESSIONS
Fundamentals of Characters and Fundamentals of Characters and StringsStrings
We write string literals as sequences of characters in double quotation marks:
A declaration can assign a String literal to a String variable:
Dim color As String = “Blue”Dim color As String = “Blue”
“Gerick Andrei M. Salalima" “257-G Teresa St." “Sta. Mesa, Manila" "(632) 4689900"
“Gerick Andrei M. Salalima" “257-G Teresa St." “Sta. Mesa, Manila" "(632) 4689900"
Visual Basic 2005
Strings, Characters and Regular Expressions
5STRINGS, CHARACTERS AND REGULAR EXPRESSIONS
String ConstructorsString Constructors
Class String provides constructors for initializing Strings
' string initialization originalString = "Welcome to VB programming!" string1 = originalString string2 = New String(characterArray) string3 = New String(characterArray, 6, 3) string4 = New String("C"c, 5)
' string initialization originalString = "Welcome to VB programming!" string1 = originalString string2 = New String(characterArray) string3 = New String(characterArray, 6, 3) string4 = New String("C"c, 5)
Visual Basic 2005
Strings, Characters and Regular Expressions
6STRINGS, CHARACTERS AND REGULAR EXPRESSIONS
String ConstructorsString Constructors
Sample program
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 7
Visual Basic 2005
Strings, Characters and Regular Expressions
‘Demonstrating String class constructorsModule StringConstructor Sub Main() Dim originalString, string1, string2, _ string3, string4 As String Dim characterArray() As Char = _ {"b"c, "i"c, "r"c, "t"c, "h"c, " "c, "d"c, "a"c, "y"c}
' string initialization originalString = "Welcome to VB programming!" string1 = originalString string2 = New String(characterArray) string3 = New String(characterArray, 6, 3) string4 = New String("C"c, 5) Console.WriteLine("string1 = " & """" & string1 & _ """" & vbCrLf & "string2 = " & """" & string2 & _ """" & vbCrLf & "string3 = " & """" & string3 & _ """" & vbCrLf & "string4 = " & """" & string4 & _ """" & vbCrLf) End Sub ' Main End Module ' StringConstructor
‘Demonstrating String class constructorsModule StringConstructor Sub Main() Dim originalString, string1, string2, _ string3, string4 As String Dim characterArray() As Char = _ {"b"c, "i"c, "r"c, "t"c, "h"c, " "c, "d"c, "a"c, "y"c}
' string initialization originalString = "Welcome to VB programming!" string1 = originalString string2 = New String(characterArray) string3 = New String(characterArray, 6, 3) string4 = New String("C"c, 5) Console.WriteLine("string1 = " & """" & string1 & _ """" & vbCrLf & "string2 = " & """" & string2 & _ """" & vbCrLf & "string3 = " & """" & string3 & _ """" & vbCrLf & "string4 = " & """" & string4 & _ """" & vbCrLf) End Sub ' Main End Module ' StringConstructor
String ConstructorsString Constructors
Output
Visual Basic 2005
Strings, Characters and Regular Expressions
8STRINGS, CHARACTERS AND REGULAR EXPRESSIONS
string1 = "Welcome to VB programming!" string2 = "birth day" string3 = "day" string4 = "CCCCC"
string1 = "Welcome to VB programming!" string2 = "birth day" string3 = "day" string4 = "CCCCC"
StringString Indexer, Indexer, LengthLength Property and Property and CopyToCopyTo Method Method
The String indexer is used to access individual characters in a String
The property Length returns the length of the String
The CopyTo method copies a specified number of characters from a String into a Char array
Visual Basic 2005
Strings, Characters and Regular Expressions
9STRINGS, CHARACTERS AND REGULAR EXPRESSIONS
StringString Indexer, Indexer, LengthLength Property and Property and CopyToCopyTo Method Method
Using the indexer, property Length and method CopyTo
Visual Basic 2005
Strings, Characters and Regular Expressions
10STRINGS, CHARACTERS AND REGULAR EXPRESSIONS
Dim string1 As String = “Hello there”Dim i As Integer
For i = string1.Length - 1 To 0 Step -1 Console.Write(string1(i)) Next i
Dim string1 As String = “Hello there”Dim i As Integer
For i = string1.Length - 1 To 0 Step -1 Console.Write(string1(i)) Next i
Dim len As Integer
len = string1.Length
Dim len As Integer
len = string1.Length
Dim characterArray() As Char
' copy characters from string1 into characterArraystring1.CopyTo(0, characterArray, 0, 5)
Dim characterArray() As Char
' copy characters from string1 into characterArraystring1.CopyTo(0, characterArray, 0, 5)
Comparing StringsComparing Strings
Comparing Strings with = and String Methods Equals and CompareTo
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 11
' test for equality with = If string1 = "hello” Then Console.WriteLine("string1 equals ""hello""") End If
' test for equality with = If string1 = "hello” Then Console.WriteLine("string1 equals ""hello""") End If
' test for equality using Equals methodIf string1.Equals("hello") Then Console.WriteLine("string1 equals ""hello""") End If
' test for equality using Equals methodIf string1.Equals("hello") Then Console.WriteLine("string1 equals ""hello""") End If
' test CompareToIf string1.CompareTo("hello") = 0 Then Console.WriteLine("string1 equals ""hello""") Else Console.WriteLine("string1 not equal to ""hello""")End If
' test CompareToIf string1.CompareTo("hello") = 0 Then Console.WriteLine("string1 equals ""hello""") Else Console.WriteLine("string1 not equal to ""hello""")End If
Visual Basic 2005
Strings, Characters and Regular Expressions
Locating Characters and Substrings in Locating Characters and Substrings in StringStringss
In many applications, it is necessary to search for a character or set of characters in a String
For example, a programmer creating a word processor would want to provide capabilities for searching through documents
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 12
Visual Basic 2005
Strings, Characters and Regular Expressions
Locating Characters and Substrings in Locating Characters and Substrings in StringStringss
Searching for characters and substrings in Strings
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 13
Dim letters As String = "abcdefghijklmabcdefghijklm“Dim searchLetters As Char () = {"c"c, "a"c, "$"c}Dim index As Integer
index = letters.IndexOf("c"c) ‘this returns 2. . .index = letters.IndexOf("a"c, 1) ‘this returns 13. . .index = letters.IndexOf("$"c, 3, 5) ‘this returns -1
Dim letters As String = "abcdefghijklmabcdefghijklm“Dim searchLetters As Char () = {"c"c, "a"c, "$"c}Dim index As Integer
index = letters.IndexOf("c"c) ‘this returns 2. . .index = letters.IndexOf("a"c, 1) ‘this returns 13. . .index = letters.IndexOf("$"c, 3, 5) ‘this returns -1
Character to be located
Starting index where search begins
No of characters to seek
IndexOf retruns the index of the first occurrence of the
character in the string
Visual Basic 2005
Strings, Characters and Regular Expressions
Locating Characters and Substrings in Locating Characters and Substrings in StringStringss
Searching for characters and substrings in Strings
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 14
Dim letters As String = "abcdefghijklmabcdefghijklm“Dim searchLetters As Char () = {"c"c, "a"c, "$"c}Dim index As Integer
index = letters.LastIndexOf("c"c) ‘this returns 15. . .index = letters.LastIndexOf("a"c, 25) ‘this returns 13. . .index = letters.LastIndexOf("$"c, 15, 5) ‘this returns -1
Dim letters As String = "abcdefghijklmabcdefghijklm“Dim searchLetters As Char () = {"c"c, "a"c, "$"c}Dim index As Integer
index = letters.LastIndexOf("c"c) ‘this returns 15. . .index = letters.LastIndexOf("a"c, 25) ‘this returns 13. . .index = letters.LastIndexOf("$"c, 15, 5) ‘this returns -1
Character to be located
Starting index where search begins
No of characters to seek
LastIndexOf retruns the index of the last occurrence of the character in the string
Visual Basic 2005
Strings, Characters and Regular Expressions
Locating Characters and Substrings in Locating Characters and Substrings in StringStringss
Searching for characters and substrings in Strings
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 15
Dim letters As String = "abcdefghijklmabcdefghijklm“Dim searchLetters As Char () = {"c"c, "a"c, "$"c}Dim index As Integer
index = letters.IndexOfAny(searchLetters) ‘this returns 0. . .index = letters.IndexOfAny(searchLetters, 7) ‘this returns 13. . .index = letters.IndexOfAny(searchLetters, 7, 5) ‘this returns -1
Dim letters As String = "abcdefghijklmabcdefghijklm“Dim searchLetters As Char () = {"c"c, "a"c, "$"c}Dim index As Integer
index = letters.IndexOfAny(searchLetters) ‘this returns 0. . .index = letters.IndexOfAny(searchLetters, 7) ‘this returns 13. . .index = letters.IndexOfAny(searchLetters, 7, 5) ‘this returns -1
IndexOfAny retruns the index of the first occurrence in the string of any character
in a specified array of unicode characters
Visual Basic 2005
Strings, Characters and Regular Expressions
Locating Characters and Substrings in Locating Characters and Substrings in StringStringss
Searching for characters and substrings in Strings
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 16
Dim letters As String = "abcdefghijklmabcdefghijklm“Dim searchLetters As Char () = {"c"c, "a"c, "$"c}Dim index As Integer
index = letters.LastIndexOfAny(searchLetters) ‘this returns 15. . .index = letters.LastIndexOfAny(searchLetters, 1) ‘this returns 0. . .index = letters.LastIndexOfAny(searchLetters, 25, 5)‘this returns -1
Dim letters As String = "abcdefghijklmabcdefghijklm“Dim searchLetters As Char () = {"c"c, "a"c, "$"c}Dim index As Integer
index = letters.LastIndexOfAny(searchLetters) ‘this returns 15. . .index = letters.LastIndexOfAny(searchLetters, 1) ‘this returns 0. . .index = letters.LastIndexOfAny(searchLetters, 25, 5)‘this returns -1
LastIndexOfAny retruns the index of the last
occurrence in the string of any character in a specified array of unicode characters
Visual Basic 2005
Strings, Characters and Regular Expressions
Extracting Substrings From Extracting Substrings From StringStringss
Class String provides two Substring methods, which are used to create a new String by copying part of an existing String
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 17
Dim letters As String = "abcdefghijklmabcdefghijklm“Dim output As String = “”
output = letters.Substring(20) ‘output gets hijklm. . .output = letters.Substring(0, 6) ‘output gets abcdef. . .
Dim letters As String = "abcdefghijklmabcdefghijklm“Dim output As String = “”
output = letters.Substring(20) ‘output gets hijklm. . .output = letters.Substring(0, 6) ‘output gets abcdef. . .
Starting index No of characters to extract from starting index
Visual Basic 2005
Strings, Characters and Regular Expressions
Concatenating Concatenating StringStringss
Like the & operator, the String class's Shared method Concat can be used to concatenate two Strings
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 18
Dim string1 As String = “Visual “Dim string2 As String = “Basic”Dim newString As String
newString = String.Concat(string1, string2) ‘newString gets Visual Basic. . .
Dim string1 As String = “Visual “Dim string2 As String = “Basic”Dim newString As String
newString = String.Concat(string1, string2) ‘newString gets Visual Basic. . .
Concat method
Visual Basic 2005
Strings, Characters and Regular Expressions
Miscellaneous Miscellaneous StringString Methods Methods
Class String provides several methods that return modified copies of Strings
String methods Replace, ToLower, ToUpper and Trim:
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 19
Dim string1 As String = “cheers!“Dim string2 As String = “GOOD BYE ”Dim string3 As String = “ spaces “Dim output As String
output = string1.Replace(“e”c, “E”c) ‘output gets “chEErs!”. . .output = string1.ToUpper() ‘output gets “CHEERS!”. . .output = string2.ToLower() ‘output gets “good bye” . . .output = string3.Trim() ‘output gets “spaces”. . .
Dim string1 As String = “cheers!“Dim string2 As String = “GOOD BYE ”Dim string3 As String = “ spaces “Dim output As String
output = string1.Replace(“e”c, “E”c) ‘output gets “chEErs!”. . .output = string1.ToUpper() ‘output gets “CHEERS!”. . .output = string2.ToLower() ‘output gets “good bye” . . .output = string3.Trim() ‘output gets “spaces”. . .
Visual Basic 2005
Strings, Characters and Regular Expressions
Class Class StringBuilderStringBuilder
Objects of class String are constant strings, whereas object of class StringBuilder are mutable sequences of characters
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 20
' Demonstrating StringBuilder class constructors. Imports System.Text
Module StringBuilderConstructor Sub Main() Dim buffer1, buffer2, buffer3 As StringBuilder
buffer1 = New StringBuilder() buffer2 = New StringBuilder(10) buffer3 = New StringBuilder("hello") Console.WriteLine("buffer1 = """ & buffer1.ToString() & """") Console.WriteLine("buffer2 = """ & buffer2.ToString() & """") Console.WriteLine("buffer3 = """ & buffer3.ToString() & """") End Sub ' Main End Module ' StringBuilderConstructor
' Demonstrating StringBuilder class constructors. Imports System.Text
Module StringBuilderConstructor Sub Main() Dim buffer1, buffer2, buffer3 As StringBuilder
buffer1 = New StringBuilder() buffer2 = New StringBuilder(10) buffer3 = New StringBuilder("hello") Console.WriteLine("buffer1 = """ & buffer1.ToString() & """") Console.WriteLine("buffer2 = """ & buffer2.ToString() & """") Console.WriteLine("buffer3 = """ & buffer3.ToString() & """") End Sub ' Main End Module ' StringBuilderConstructor
Visual Basic 2005
Strings, Characters and Regular Expressions
LengthLength and and CapacityCapacity Properties, Properties, EnsureCapacityEnsureCapacity Method and Indexer of Class Method and Indexer of Class StringBuilderStringBuilder
Class StringBuilder provides the Length and Capacity properties to return the number of characters currently in a StringBuilder and the number of characters that a StringBuilder can store without allocating more memory, respectively
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 21
Visual Basic 2005
Strings, Characters and Regular Expressions
LengthLength and and CapacityCapacity Properties, Properties, EnsureCapacityEnsureCapacity Method and Indexer of Class Method and Indexer of Class StringBuilderStringBuilder
StringBuilder size manipulation
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 22
Dim buffer As New StringBuilder("Hello, how are you?")
Console.WriteLine(buffer.ToString())Console.WriteLine(“Length = “ & buffer.Length)Console.WriteLine(“Capacity = “ & buffer.Capacity)
buffer.EnsureCapacity(75)Buffer.Length = 10
Console.WriteLine(buffer.ToString())
Dim buffer As New StringBuilder("Hello, how are you?")
Console.WriteLine(buffer.ToString())Console.WriteLine(“Length = “ & buffer.Length)Console.WriteLine(“Capacity = “ & buffer.Capacity)
buffer.EnsureCapacity(75)Buffer.Length = 10
Console.WriteLine(buffer.ToString())
Hello, how are you?Length = 19Capacity = 32Hello, how
Hello, how are you?Length = 19Capacity = 32Hello, how
Visual Basic 2005
Strings, Characters and Regular Expressions
AppendAppend and and AppendFormatAppendFormat Methods of Methods of Class Class StringBuilderStringBuilder
Class StringBuilder provides 19 overloaded Append methods for appending values of various types to the end of a StringBuilder's contents
There are versions of this method for each of the primitive types and for character arrays, Strings and Objects
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 23
Visual Basic 2005
Strings, Characters and Regular Expressions
AppendAppend and and AppendFormatAppendFormat Methods of Methods of Class Class StringBuilderStringBuilder
Append methods of StringBuilder
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 24
Dim objectValue As Object = "hello“ Dim stringValue As String = "good bye“ Dim characterArray As Char() = {"a"c, "b"c, "c"c, "d"c, "e"c, "f"c} Dim booleanValue As Boolean = True Dim characterValue As Char = "Z"c Dim integerValue As Integer = 7 Dim longValue As Long = 1000000 Dim floatValue As Single = 2.5F ' F indicates that 2.5 is a float Dim doubleValue As Double = 33.333 Dim buffer As New StringBuilder()
' use method Append to append values to buffer buffer.Append(objectValue) buffer.Append(" ") buffer.Append(stringValue) buffer.Append(" ") buffer.Append(characterArray) buffer.Append(" “)buffer.Append(integerValue). . .
Dim objectValue As Object = "hello“ Dim stringValue As String = "good bye“ Dim characterArray As Char() = {"a"c, "b"c, "c"c, "d"c, "e"c, "f"c} Dim booleanValue As Boolean = True Dim characterValue As Char = "Z"c Dim integerValue As Integer = 7 Dim longValue As Long = 1000000 Dim floatValue As Single = 2.5F ' F indicates that 2.5 is a float Dim doubleValue As Double = 33.333 Dim buffer As New StringBuilder()
' use method Append to append values to buffer buffer.Append(objectValue) buffer.Append(" ") buffer.Append(stringValue) buffer.Append(" ") buffer.Append(characterArray) buffer.Append(" “)buffer.Append(integerValue). . .
Visual Basic 2005
Strings, Characters and Regular Expressions
InsertInsert, , RemoveRemove and and ReplaceReplace Methods of Methods of Class Class StringBuilderStringBuilder
Class StringBuilder provides 18 overloaded Insert methods to allow values of various types to be inserted at any position in a StringBuilder
There are versions of Insert for each of the primitive types and for character arrays, Strings and Objects
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 25
Visual Basic 2005
Strings, Characters and Regular Expressions
InsertInsert, , RemoveRemove and and ReplaceReplace Methods of Methods of Class Class StringBuilderStringBuilder
StringBuilder text insertion and removal
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 26
Dim buffer As New StringBuilder("Hello, how are you?")
Console.WriteLine(buffer.ToString())buffer.Insert(18, " Gerick")Console.WriteLine(buffer.ToString())buffer.Replace(“Gerick", “Rainne")Console.WriteLine(buffer.ToString())buffer.Remove(18, 7)Console.WriteLine(buffer.ToString())
Dim buffer As New StringBuilder("Hello, how are you?")
Console.WriteLine(buffer.ToString())buffer.Insert(18, " Gerick")Console.WriteLine(buffer.ToString())buffer.Replace(“Gerick", “Rainne")Console.WriteLine(buffer.ToString())buffer.Remove(18, 7)Console.WriteLine(buffer.ToString())
Hello, how are you?Hello, how are you Gerick?Hello, how are you Rainne?Hello, how are you?
Hello, how are you?Hello, how are you Gerick?Hello, how are you Rainne?Hello, how are you?
Visual Basic 2005
Strings, Characters and Regular Expressions
CharChar Methods Methods
Many of the primitive types that we have used are actually aliases for different structures
For instance, an Integer is defined by structure System.Int32, a Long by System.Int64 and so on
Char, is the structure for charactersMost Char methods are Shared
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 27
Visual Basic 2005
Strings, Characters and Regular Expressions
CharChar Methods Methods
Char's Shared character-testing and case-conversion methods
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 28
Dim character As Char = “A”cDim output As String
output = "is digit: " & Char.IsDigit(character) & vbCrLf output &= "is letter: " & Char.IsLetter(character) & vbCrLf output &= "is letter or digit: " & _ Char.IsLetterOrDigit(character) & vbCrLf output &= "is lowercase: " & Char.IsLower(character) & vbCrLf output &= "is uppercase: " & Char.IsUpper(character) & vbCrLf output &= "to uppercase: " & Char.ToUpper(character) & vbCrLf output &= "to lowercase: " & Char.ToLower(character) & vbCrLf output &= "is punctuation: " & _ Char.IsPunctuation(character) & vbCrLf output &= "is symbol: " & Char.IsSymbol(character)
Console.WriteLine(output)
Dim character As Char = “A”cDim output As String
output = "is digit: " & Char.IsDigit(character) & vbCrLf output &= "is letter: " & Char.IsLetter(character) & vbCrLf output &= "is letter or digit: " & _ Char.IsLetterOrDigit(character) & vbCrLf output &= "is lowercase: " & Char.IsLower(character) & vbCrLf output &= "is uppercase: " & Char.IsUpper(character) & vbCrLf output &= "to uppercase: " & Char.ToUpper(character) & vbCrLf output &= "to lowercase: " & Char.ToLower(character) & vbCrLf output &= "is punctuation: " & _ Char.IsPunctuation(character) & vbCrLf output &= "is symbol: " & Char.IsSymbol(character)
Console.WriteLine(output)
Visual Basic 2005
Strings, Characters and Regular Expressions
CharChar Methods Methods
Char's Shared character-testing and case-conversion methods
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 29
is digit: Falseis letter: Trueis letter or digit: Trueis lowercase: Falseis uppercase: Trueto uppercase: Ato lowercase: ais punctuation: Falseis symbol: False
is digit: Falseis letter: Trueis letter or digit: Trueis lowercase: Falseis uppercase: Trueto uppercase: Ato lowercase: ais punctuation: Falseis symbol: False
Visual Basic 2005
Strings, Characters and Regular Expressions
Regular Expressions and Class Regular Expressions and Class RegExRegEx
Regular expressions are specially formatted Strings used to find (and possibly replace) patterns in text
They can be useful during information validation, to ensure that data is in a particular format
For example, a Philippine ZIP code must consist of four digits, and a last name must start with a capital letter
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 30
Visual Basic 2005
Strings, Characters and Regular Expressions
Regular Expressions and Class Regular Expressions and Class RegExRegEx
Regular expression character classes:
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 31
Visual Basic 2005
Character class Matches Character class Matches
\d Any digit \D Any non-digit
\w Any word character \W Any non-word character
\s Any whitespace \S Any non-whitespace
Strings, Characters and Regular Expressions
Regular Expressions and Class Regular Expressions and Class RegExRegEx
Regular expressions checking birthdays
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 32
Visual Basic 2005
‘ Demonstrating Class Regex. Imports System.Text.RegularExpressions
Module RegexMatches Sub Main() ' create regular expression Dim expression As New Regex("J.*\d[0-35-9]-\d\d-\d\d") Dim string1 As String = _ "Jane's Birthday is 05-12-75" & vbCrLf & _ "Dave's Birthday is 11-04-68" & vbCrLf & _ "John's Birthday is 04-28-73" & vbCrLf & _ "Joe's Birthday is 12-17-77"
' match regular expression to string and ' print out all matches For Each myMatch As Match In expression.Matches(string1) Console.WriteLine(myMatch) Next myMatch End Sub ' Main End Module ' RegexMatches
‘ Demonstrating Class Regex. Imports System.Text.RegularExpressions
Module RegexMatches Sub Main() ' create regular expression Dim expression As New Regex("J.*\d[0-35-9]-\d\d-\d\d") Dim string1 As String = _ "Jane's Birthday is 05-12-75" & vbCrLf & _ "Dave's Birthday is 11-04-68" & vbCrLf & _ "John's Birthday is 04-28-73" & vbCrLf & _ "Joe's Birthday is 12-17-77"
' match regular expression to string and ' print out all matches For Each myMatch As Match In expression.Matches(string1) Console.WriteLine(myMatch) Next myMatch End Sub ' Main End Module ' RegexMatches
Strings, Characters and Regular Expressions
Regular Expressions and Class Regular Expressions and Class RegExRegEx
Quantifiers used in regular expressions
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 33
Visual Basic 2005
Quantifier Matches
* Matches zero or more occurrences of the preceding pattern.
+ Matches one or more occurrences of the preceding pattern.
? Matches zero or one occurrences of the preceding pattern.
{n} Matches exactly n occurrences of the preceding pattern.
{n,} Matches at least n occurrences of the preceding pattern.
{n,m} Matches between n and m (inclusive) occurrences of the preceding pattern.
Strings, Characters and Regular Expressions
Regular Expressions and Class Regular Expressions and Class RegExRegEx
Validating user information using regular expressions
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 34
Visual Basic 2005
Dim strLastName As String = "Salalima"
If Regex.Match(strLastName, "^[A-Z][a-zA-Z]*$").Success Then MessageBox.Show("Valid last name", "Message", _ MessageBoxButtons.OK, MessageBoxIcon.Information)Else MessageBox.Show("Invalid last name", "Message", _ MessageBoxButtons.OK, MessageBoxIcon.Error)End If
Dim strLastName As String = "Salalima"
If Regex.Match(strLastName, "^[A-Z][a-zA-Z]*$").Success Then MessageBox.Show("Valid last name", "Message", _ MessageBoxButtons.OK, MessageBoxIcon.Information)Else MessageBox.Show("Invalid last name", "Message", _ MessageBoxButtons.OK, MessageBoxIcon.Error)End If
Strings, Characters and Regular Expressions
Regular Expressions and Class Regular Expressions and Class RegExRegEx
Validating user information using regular expressions
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 35
Visual Basic 2005
Dim strAddress As String = "257-G Teresa St."
If Regex.Match(strAddress, _ "^[0-9]+\s+([a-zA-Z]+|[a-zA-Z]+\s[a-zA-Z]+)$").Success Then MessageBox.Show("Valid address", "Message", _ MessageBoxButtons.OK, MessageBoxIcon.Information)Else MessageBox.Show("Invalid address", "Message", _ MessageBoxButtons.OK, MessageBoxIcon.Error)End If
Dim strAddress As String = "257-G Teresa St."
If Regex.Match(strAddress, _ "^[0-9]+\s+([a-zA-Z]+|[a-zA-Z]+\s[a-zA-Z]+)$").Success Then MessageBox.Show("Valid address", "Message", _ MessageBoxButtons.OK, MessageBoxIcon.Information)Else MessageBox.Show("Invalid address", "Message", _ MessageBoxButtons.OK, MessageBoxIcon.Error)End If
Strings, Characters and Regular Expressions
Regular Expressions and Class Regular Expressions and Class RegExRegEx
Validating user information using regular expressions
STRINGS, CHARACTERS AND REGULAR EXPRESSIONS 36
Visual Basic 2005
Dim strZip As String = "12345"
If Regex.Match(strZip, "^\d{5}$").Success Then MessageBox.Show("Valid zip code", "Message", _ MessageBoxButtons.OK, MessageBoxIcon.Information)Else MessageBox.Show("Invalid zip code", "Message", _ MessageBoxButtons.OK, MessageBoxIcon.Error)End If
Dim strZip As String = "12345"
If Regex.Match(strZip, "^\d{5}$").Success Then MessageBox.Show("Valid zip code", "Message", _ MessageBoxButtons.OK, MessageBoxIcon.Information)Else MessageBox.Show("Invalid zip code", "Message", _ MessageBoxButtons.OK, MessageBoxIcon.Error)End If
Strings, Characters and Regular Expressions