Strings and Text

Option Strict On

Module Ex01
    Sub Main()
        ' Quotes are doubled; there are no backslash escapes.
        Dim quoted = "She said ""Hello"" and left"
        Dim windowsPath = "C:\Shelf\catalog.json"
        Console.WriteLine(quoted)
        Console.WriteLine(windowsPath)

        ' Special characters come from constants, ControlChars or ChrW.
        Console.WriteLine("Tab:" & vbTab & "|" & ControlChars.Tab & "|")
        Console.WriteLine("Two lines:" & Environment.NewLine & "second line")
        Console.WriteLine("Euro sign: " & ChrW(&H20AC) & ", code " & AscW("€"c))
        Console.WriteLine("vbCrLf length = " & vbCrLf.Length & ", vbLf length = " & vbLf.Length)

        ' A string literal may contain line breaks (VB 14): the text includes the file's own line endings.
        Dim poem = "first
second"
        Console.WriteLine("Literal with a line break has length " & poem.Length & " and contains LF: " & poem.Contains(vbLf))

        ' Character literals use the c suffix.
        Dim letter As Char = "A"c
        Console.WriteLine(letter & " has code " & AscW(letter) & ", next is " & ChrW(AscW(letter) + 1))

        ' Interpolation: {expression,alignment:format}
        Dim title = "Dune"
        Dim year = 1965
        Dim price = 12.5D
        Console.WriteLine($"[{title,-8}] [{title,8}] {year} {price:N2}")
        Console.WriteLine($"Braces are doubled: {{{title}}}")
        Console.WriteLine($"Nested quotes are fine: {If(year > 1900, "modern", "old")}")
        Console.WriteLine($"Inside {title.ToUpperInvariant()} the calculation is {year + 1}")
    End Sub
End Module

She said "Hello" and left
C:\Shelf\catalog.json
Tab:	|	|
Two lines:
second line
Euro sign: €, code 8364
vbCrLf length = 2, vbLf length = 1
Literal with a line break has length 12 and contains LF: True
A has code 65, next is B
[Dune    ] [    Dune] 1965 12.50
Braces are doubled: {Dune}
Nested quotes are fine: modern
Inside DUNE the calculation is 1966

Option Strict On

Module Ex03
    Sub Main()
        Dim text = "Hello World!"

        Console.WriteLine("-- Mid is 1-based, Substring is 0-based")
        Console.WriteLine($"Mid(text, 6, 5)       = '{Mid(text, 6, 5)}'")
        Console.WriteLine($"text.Substring(6, 5)  = '{text.Substring(6, 5)}'")
        Console.WriteLine($"Mid(text, 7, 5)       = '{Mid(text, 7, 5)}'")
        Console.WriteLine($"Mid(text, 7)          = '{Mid(text, 7)}'")
        Console.WriteLine($"Left(text, 5)         = '{Left(text, 5)}'")
        Console.WriteLine($"Right(text, 6)        = '{Right(text, 6)}'")
        Console.WriteLine($"Left(text, 99)        = '{Left(text, 99)}'")
        Console.WriteLine($"Mid(text, 99)         = '{Mid(text, 99)}'")

        Try
            Console.WriteLine(text.Substring(99))
        Catch ex As ArgumentOutOfRangeException
            Console.WriteLine("text.Substring(99) throws " & ex.GetType().Name)
        End Try
        Try
            Console.WriteLine(Mid(text, 0, 2))
        Catch ex As ArgumentException
            Console.WriteLine("Mid(text, 0, 2) throws " & ex.GetType().Name)
        End Try

        Console.WriteLine("-- Searching: 0 means not found for InStr, -1 for IndexOf")
        Console.WriteLine($"InStr(text, ""o"")        = {InStr(text, "o")}")
        Console.WriteLine($"InStr(6, text, ""o"")     = {InStr(6, text, "o")}")
        Console.WriteLine($"InStrRev(text, ""o"")     = {InStrRev(text, "o")}")
        Console.WriteLine($"InStr(text, ""z"")        = {InStr(text, "z")}")
        Console.WriteLine($"text.IndexOf(""o"")       = {text.IndexOf("o")}")
        Console.WriteLine($"text.IndexOf(""z"")       = {text.IndexOf("z")}")
        Console.WriteLine($"text.LastIndexOf(""o"")   = {text.LastIndexOf("o")}")
        Console.WriteLine($"text.Contains(""World"")  = {text.Contains("World")}")

        Console.WriteLine("-- Trim: the VB function removes only spaces")
        Dim padded = vbTab & "  Shelf  " & vbTab
        Console.WriteLine($"Trim(padded).Length   = {Trim(padded).Length}")
        Console.WriteLine($"padded.Trim().Length  = {padded.Trim().Length}")
        Console.WriteLine($"LTrim / RTrim lengths = {LTrim(padded).Length} / {RTrim(padded).Length}")

        Console.WriteLine("-- Case, length, repeat")
        Console.WriteLine($"UCase / LCase         = {UCase(text)} / {LCase(text)}")
        Console.WriteLine($"Len(text)             = {Len(text)}")
        Console.WriteLine($"Space(3) & StrDup     = '{Space(3)}' '{StrDup(3, "ab")}'")
        Console.WriteLine($"ToTitleCase           = {System.Globalization.CultureInfo.InvariantCulture.TextInfo.ToTitleCase("the lord of the rings")}")

        Console.WriteLine("-- Replace, Split, Join")
        Console.WriteLine($"Replace(text, ""l"", ""L"")          = {Replace(text, "l", "L")}")
        Console.WriteLine($"Replace(text, ""l"", ""L"", 5)       = {Replace(text, "l", "L", 5)}")
        Console.WriteLine($"Replace(text, ""l"", ""L"", 1, 2)    = {Replace(text, "l", "L", 1, 2)}")
        Console.WriteLine($"text.Replace(""l"", ""L"")           = {text.Replace("l", "L")}")
        Dim parts = Split("a,b,,c", ",")
        Console.WriteLine($"Split keeps empty entries: {parts.Length} -> {Join(parts, "|")}")
        Dim parts2 = "a,b,,c".Split(","c, StringSplitOptions.RemoveEmptyEntries)
        Console.WriteLine($"String.Split with options: {parts2.Length} -> {String.Join("|", parts2)}")
        Console.WriteLine($"Split(""a b c"") default delimiter is a space: {Split("a b c").Length}")
        Console.WriteLine($"Split with limit: {Join(Split("a,b,c,d", ",", 2), "|")}")
        Console.WriteLine($"Filter: {Join(Filter({"ada", "alan", "grace"}, "al"), ",")}")
    End Sub
End Module

-- Mid is 1-based, Substring is 0-based
Mid(text, 6, 5)       = ' Worl'
text.Substring(6, 5)  = 'World'
Mid(text, 7, 5)       = 'World'
Mid(text, 7)          = 'World!'
Left(text, 5)         = 'Hello'
Right(text, 6)        = 'World!'
Left(text, 99)        = 'Hello World!'
Mid(text, 99)         = ''
text.Substring(99) throws ArgumentOutOfRangeException
Mid(text, 0, 2) throws ArgumentException
-- Searching: 0 means not found for InStr, -1 for IndexOf
InStr(text, "o")        = 5
InStr(6, text, "o")     = 8
InStrRev(text, "o")     = 8
InStr(text, "z")        = 0
text.IndexOf("o")       = 4
text.IndexOf("z")       = -1
text.LastIndexOf("o")   = 7
text.Contains("World")  = True
-- Trim: the VB function removes only spaces
Trim(padded).Length   = 11
padded.Trim().Length  = 5
LTrim / RTrim lengths = 11 / 11
-- Case, length, repeat
UCase / LCase         = HELLO WORLD! / hello world!
Len(text)             = 12
Space(3) & StrDup     = '   ' 'aaa'
ToTitleCase           = The Lord Of The Rings
-- Replace, Split, Join
Replace(text, "l", "L")          = HeLLo WorLd!
Replace(text, "l", "L", 5)       = o WorLd!
Replace(text, "l", "L", 1, 2)    = HeLLo World!
text.Replace("l", "L")           = HeLLo WorLd!
Split keeps empty entries: 4 -> a|b||c
String.Split with options: 3 -> a|b|c
Split("a b c") default delimiter is a space: 3
Split with limit: a|b,c,d
Filter: alan

Option Strict On
Imports System.Text

Module Ex08
    Sub Main()
        Dim titles As String() = {"Dune", "Emma", "Ulysses"}

        Dim csv = String.Join(",", titles)
        Console.WriteLine(csv)
        Console.WriteLine(String.Concat("a", "b", "c") & String.Concat(titles))
        Console.WriteLine(String.Join(", ", titles.Select(Function(t) t.Length)))

        ' Repeated & in a loop copies the whole string each time: O(n squared).
        Dim slow = ""
        For i = 1 To 5
            slow &= i & ";"
        Next
        Console.WriteLine(slow)

        Dim builder As New StringBuilder()
        For Each t In titles
            If builder.Length > 0 Then builder.Append(" | ")
            builder.Append(t).Append(" (").Append(t.Length).Append(")"c)
        Next
        builder.AppendLine().AppendFormat("{0} titles", titles.Length)
        builder.Insert(0, ">> ")
        Console.WriteLine(builder.ToString())
        Console.WriteLine($"Length = {builder.Length}, capacity >= length: {builder.Capacity >= builder.Length}")
        builder.Clear()
        Console.WriteLine($"After Clear: Length = {builder.Length}")

        ' Spans can be used inside one expression, but a local variable cannot have a span type in VB.
        Dim isbn = "978-0-441-17271-9"
        Console.WriteLine($"Span slice: {isbn.AsSpan(4, 1).ToString()}, length {isbn.AsSpan(4, 1).Length}")
        Console.WriteLine($"Span search: {isbn.AsSpan().IndexOf("-"c)}")
        Dim digits = isbn.Where(AddressOf Char.IsDigit).Count()
        Console.WriteLine($"Digits via LINQ: {digits}")

        Console.WriteLine($"String.Format: {String.Format("{0,-6}|{1,6:N1}|{2:P0}", "Dune", 12.34, 0.256)}")
        Dim invariantText = FormattableString.Invariant($"{1234.5:N2} on {#2026-10-19#:yyyy-MM-dd}")
        Console.WriteLine(invariantText)
        Dim f As FormattableString = $"{titles(0)} and {titles(1)}"
        Console.WriteLine($"Format = '{f.Format}', ArgumentCount = {f.ArgumentCount}")
    End Sub
End Module

Dune,Emma,Ulysses
abcDuneEmmaUlysses
4, 4, 7
1;2;3;4;5;
>> Dune (4) | Emma (4) | Ulysses (7)
3 titles
Length = 45, capacity >= length: True
After Clear: Length = 0
Span slice: 0, length 1
Span search: 3
Digits via LINQ: 13
String.Format: Dune  |  12.3|26 %
1,234.50 on 2026-10-19
Format = '{0} and {1}', ArgumentCount = 2

Option Strict On

Module Ex12
    Sub Check(text As String, pattern As String)
        Console.WriteLine($"{text,-12} Like {pattern,-12} -> {text Like pattern}")
    End Sub

    Sub Main()
        Check("Dune", "D*")
        Check("Dune", "D??e")
        Check("Dune", "d*")
        Check("2026", "####")
        Check("A12", "[A-C]##")
        Check("D12", "[!A-C]##")
        Check("a*b", "a[*]b")
        Check("978-0-441", "978-#-###")
        Check("ISBN", "")

        Dim padded = "Dune".PadRight(8, "."c) & "1965".PadLeft(6)
        Console.WriteLine(padded)
        Dim catalog As (Title As String, Year As Integer)() = {("Dune", 1965), ("Emma", 1815), ("Ulysses", 1922)}
        For Each row In catalog
            Console.WriteLine($"{row.Title,-10}{row.Year,6}")
        Next
        Console.WriteLine(New String("="c, 16))
    End Sub
End Module

Dune         Like D*           -> True
Dune         Like D??e         -> True
Dune         Like d*           -> False
2026         Like ####         -> True
A12          Like [A-C]##      -> True
D12          Like [!A-C]##     -> True
a*b          Like a[*]b        -> True
978-0-441    Like 978-#-###    -> True
ISBN         Like              -> False
Dune....  1965
Dune        1965
Emma        1815
Ulysses     1922
================

Option Strict On
Imports System.Text.RegularExpressions

Module Ex09
    Sub Main()
        Dim lines As String() = {
            "Dune (1965) by Frank Herbert, ISBN 978-0-441-17271-9",
            "Emma (1815) by Jane Austen",
            "no year here"
        }

        ' Verbatim by nature: backslashes in VB string literals are ordinary characters.
        Dim pattern As New Regex("^(?<title>.+?) \((?<year>\d{4})\)(?: by (?<author>[^,]+))?", RegexOptions.CultureInvariant, TimeSpan.FromSeconds(1))

        For Each line In lines
            Dim m = pattern.Match(line)
            If m.Success Then
                Dim author = m.Groups("author").Value
                Console.WriteLine($"{m.Groups("title").Value} | {CInt(m.Groups("year").Value) + 1} | {If(m.Groups("author").Success, author, "(none)")}")
            Else
                Console.WriteLine($"No match: {line}")
            End If
        Next

        Dim isbn = New Regex("\b97[89](?:-?\d){10}\b")
        Console.WriteLine($"ISBN found: {isbn.Match(lines(0)).Value}")

        Dim spaced = Regex.Replace("a    b   c", "\s+", " ")
        Console.WriteLine(spaced)
        Dim shouted = Regex.Replace("shelf catalog", "\b[a-z]", Function(m As Match) m.Value.ToUpperInvariant())
        Console.WriteLine(shouted)
        Console.WriteLine(String.Join("|", Regex.Split("one, two;three", "[,;]\s*")))
        Console.WriteLine($"IsMatch ignoring case: {Regex.IsMatch("ISBN", "isbn", RegexOptions.IgnoreCase)}")
        Console.WriteLine($"Escaped user input: {Regex.Escape("1+1=2 (really?)")}")
        Console.WriteLine($"Count of digits: {Regex.Matches("a1b22c333", "\d+").Count}")

        Try
            Dim slow As New Regex("^(a+)+$", RegexOptions.None, TimeSpan.FromMilliseconds(50))
            slow.IsMatch(New String("a"c, 40) & "!")
        Catch ex As RegexMatchTimeoutException
            Console.WriteLine("RegexMatchTimeoutException after " & ex.MatchTimeout.TotalMilliseconds & " ms")
        End Try
    End Sub
End Module

Dune | 1966 | Frank Herbert
Emma | 1816 | Jane Austen
No match: no year here
ISBN found: 978-0-441-17271-9
a b c
Shelf Catalog
one|two|three
IsMatch ignoring case: True
Escaped user input: 1\+1=2\ \(really\?\)
Count of digits: 3
RegexMatchTimeoutException after 50 ms

Option Strict On
Imports System.Text

Module Ex10
    Sub Main()
        Dim text = "Caf" & ChrW(&HE9) & " " & ChrW(&H20AC)

        Console.WriteLine($"UTF-16 code units: {text.Length}")
        For Each name In {"utf-8", "utf-16", "utf-16BE", "utf-32", "us-ascii", "iso-8859-1"}
            Dim enc = Encoding.GetEncoding(name)
            Dim bytes = enc.GetBytes(text)
            Console.WriteLine($"{enc.WebName,-12} {bytes.Length,2} bytes: {Convert.ToHexString(bytes)}")
        Next

        ' Bytes that are not valid in the encoding are replaced, silently by default.
        Dim latin = Encoding.Latin1.GetBytes(text)
        Console.WriteLine($"Latin-1 round trip: {Encoding.Latin1.GetString(latin)}")
        Dim strict = Encoding.GetEncoding("us-ascii", New EncoderExceptionFallback(), New DecoderExceptionFallback())
        Try
            strict.GetBytes(text)
        Catch ex As EncoderFallbackException
            Console.WriteLine("EncoderFallbackException for U+" & AscW(ex.CharUnknown).ToString("X4"))
        End Try

        Dim utf8Bom = New UTF8Encoding(encoderShouldEmitUTF8Identifier:=True).GetPreamble()
        Console.WriteLine($"UTF-8 BOM: {Convert.ToHexString(utf8Bom)}; Encoding.UTF8 preamble: {Convert.ToHexString(Encoding.UTF8.GetPreamble())}")

        Dim broken As Byte() = {&H43, &HFF, &H44}
        Console.WriteLine($"Invalid UTF-8 decodes with a replacement character: {Encoding.UTF8.GetString(broken)} (U+{AscW(Encoding.UTF8.GetString(broken)(1)):X4})")

        Try
            Encoding.GetEncoding(1252)
        Catch ex As NotSupportedException
            Console.WriteLine("Code page 1252 needs the CodePages provider: " & ex.GetType().Name)
        End Try
        Try
            Console.WriteLine("Chr(200) = " & Chr(200))
        Catch ex As NotSupportedException
            Console.WriteLine("Chr(200) uses the ANSI code page too: " & ex.GetType().Name)
        End Try
        Encoding.RegisterProvider(CodePagesEncodingProvider.Instance)
        Console.WriteLine($"After RegisterProvider: {Encoding.GetEncoding(1252).WebName}, euro = {Convert.ToHexString(Encoding.GetEncoding(1252).GetBytes(ChrW(&H20AC)))}")

        Console.WriteLine($"Asc(""A"") = {Asc("A")}, Chr(65) = {Chr(65)}, AscW(""€"") = {AscW("€")}")
        Console.WriteLine($"After the provider is registered Chr(200) = {Chr(200)}; ChrW(200) = {ChrW(200)} regardless")
        Console.WriteLine($"Base64: {Convert.ToBase64String(Encoding.UTF8.GetBytes("Shelf"))}")
    End Sub
End Module

UTF-16 code units: 6
utf-8         9 bytes: 436166C3A920E282AC
utf-16       12 bytes: 430061006600E9002000AC20
utf-16BE     12 bytes: 00430061006600E9002020AC
utf-32       24 bytes: 430000006100000066000000E900000020000000AC200000
us-ascii      6 bytes: 4361663F203F
iso-8859-1    6 bytes: 436166E9203F
Latin-1 round trip: Café ?
EncoderFallbackException for U+00E9
UTF-8 BOM: EFBBBF; Encoding.UTF8 preamble: EFBBBF
Invalid UTF-8 decodes with a replacement character: C�D (U+FFFD)
Code page 1252 needs the CodePages provider: NotSupportedException
Chr(200) uses the ANSI code page too: NotSupportedException
After RegisterProvider: windows-1252, euro = 80
Asc("A") = 65, Chr(65) = A, AscW("€") = 8364
After the provider is registered Chr(200) = È; ChrW(200) = È regardless
Base64: U2hlbGY=

Option Strict On

Module Ex11
    Sub Main()
        Dim count As Integer = 2
        Dim title As String = "Dune"

        ' & always concatenates and converts both sides to String.
        Console.WriteLine("Copies: " & count)
        Console.WriteLine(1 & 2)
        Console.WriteLine("Total: " & 1 + 2)
        Console.WriteLine("Total: " & (1 + 2))
        Console.WriteLine(title & Nothing & "!")

        ' Concatenation has lower precedence than arithmetic and higher than comparison.
        Console.WriteLine("a" & "b" = "ab")

        ' + on two strings concatenates as well, but it is a numeric operator that falls back to concatenation.
        Dim left As String = "10"
        Dim right As String = "5"
        Console.WriteLine(left + right)
        Console.WriteLine(left & right)
        Console.WriteLine(CInt(left) + CInt(right))

        ' Interpolation and String.Format never ask whether + was meant.
        Console.WriteLine($"{left}{right} / {count + 1}")
    End Sub
End Module

Copies: 2
12
Total: 3
Total: 3
Dune!
True
105
105
15
105 / 3