`Len` Function

Returns a Long containing the number of characters in a string or the number of bytes required to store a variable.

Syntax

Len(string | varname)

Parameters

string (Optional): Any valid string expression
If string contains Null, Null is returned
varname (Optional): Any valid variable name
For user-defined types, returns size in bytes
For objects, may return implementation-defined value

Return Value

Returns a Long: - For strings: Number of characters in the string - For variables: Number of bytes required to store the variable - Returns 0 for empty string ("") - Returns Null if string argument is Null - For fixed-length strings: Returns declared length - For Variant containing string: Returns length of string - For user-defined types: Returns total size in bytes

Remarks

The Len function measures string length or variable size:

Most commonly used for string length
Returns character count, not byte count (for strings)
Empty string ("") returns 0
Null propagates through the function
Spaces and special characters are counted
For fixed-length strings (e.g., String * 10), returns declared length
Variable-length strings return actual content length
LenB function returns byte count (useful for Unicode/DBCS)
Cannot determine array size (use UBound/LBound instead)
Essential for string manipulation and validation
Used with Left, Right, Mid for substring operations
Common in loops iterating through string characters
Efficient operation with minimal overhead
For user-defined types, returns structure size
Object variables may return unpredictable values

Typical Uses

Validate Input: Check if string is empty or within length limits
String Iteration: Loop through each character in string
Substring Extraction: Calculate positions for Left/Right/Mid
Text Processing: Measure text before truncation or padding
File I/O: Determine buffer sizes for string data
Data Validation: Ensure fields meet length requirements
Format Verification: Check string format compliance
Memory Calculation: Determine structure sizes

Basic Usage Examples

' Example 1: Basic string length
Dim text As String
text = "Hello World"

Debug.Print Len(text)                ' 11 - includes space
Debug.Print Len("VB6")               ' 3
Debug.Print Len("")                  ' 0 - empty string

' Example 2: Validation
Dim password As String
password = "secret123"

If Len(password) < 8 Then
MsgBox "Password must be at least 8 characters"
End If

' Example 3: String iteration
Dim i As Long
Dim char As String
text = "ABC"

For i = 1 To Len(text)
char = Mid(text, i, 1)
Debug.Print char
Next i

' Example 4: Null handling
Dim value As Variant
value = Null

Debug.Print IsNull(Len(value))       ' True - Null propagates

Common Patterns

' Pattern 1: Check if string is empty
Function IsEmpty(text As String) As Boolean
IsEmpty = (Len(text) = 0)
End Function

' Pattern 2: Validate string length range
Function ValidateLength(text As String, minLen As Long, maxLen As Long) As Boolean
Dim length As Long
length = Len(text)
ValidateLength = (length >= minLen And length <= maxLen)
End Function

' Pattern 3: Pad string to fixed width
Function PadRight(text As String, width As Long, Optional padChar As String = " ") As String
If Len(text) >= width Then
PadRight = Left(text, width)
Else
PadRight = text & String(width - Len(text), padChar)
End If
End Function

' Pattern 4: Center text in field
Function CenterText(text As String, width As Long) As String
Dim padding As Long

If Len(text) >= width Then
CenterText = Left(text, width)
Else
padding = (width - Len(text)) \ 2
CenterText = String(padding, " ") & text & _
String(width - Len(text) - padding, " ")
End If
End Function

' Pattern 5: Reverse string
Function ReverseString(text As String) As String
Dim i As Long
Dim result As String

result = ""
For i = Len(text) To 1 Step -1
result = result & Mid(text, i, 1)
Next i

ReverseString = result
End Function

' Pattern 6: Count occurrences of character
Function CountChar(text As String, searchChar As String) As Long
Dim i As Long
Dim count As Long

count = 0
For i = 1 To Len(text)
If Mid(text, i, 1) = searchChar Then
count = count + 1
End If
Next i

CountChar = count
End Function

' Pattern 7: Truncate with ellipsis
Function TruncateText(text As String, maxLength As Long) As String
If Len(text) <= maxLength Then
TruncateText = text
ElseIf maxLength <= 3 Then
TruncateText = Left(text, maxLength)
Else
TruncateText = Left(text, maxLength - 3) & "..."
End If
End Function

' Pattern 8: Extract last N characters
Function GetLastChars(text As String, count As Long) As String
If count >= Len(text) Then
GetLastChars = text
Else
GetLastChars = Right(text, count)
End If
End Function

' Pattern 9: Check minimum length
Function HasMinLength(text As String, minLength As Long) As Boolean
HasMinLength = (Len(text) >= minLength)
End Function

' Pattern 10: Calculate character position from end
Function GetCharFromEnd(text As String, posFromEnd As Long) As String
Dim pos As Long
pos = Len(text) - posFromEnd + 1

If pos >= 1 And pos <= Len(text) Then
GetCharFromEnd = Mid(text, pos, 1)
Else
GetCharFromEnd = ""
End If
End Function

Advanced Usage Examples

' Example 1: String analyzer
Public Class StringAnalyzer
Public Function GetStats(text As String) As String
Dim length As Long
Dim words As Long
Dim lines As Long
Dim result As String

length = Len(text)
words = UBound(Split(text, " ")) + 1
lines = UBound(Split(text, vbCrLf)) + 1

result = "Length: " & length & vbCrLf
result = result & "Words: " & words & vbCrLf
result = result & "Lines: " & lines

GetStats = result
End Function

Public Function GetCharFrequency(text As String) As Object
Dim dict As Object
Dim i As Long
Dim char As String

Set dict = CreateObject("Scripting.Dictionary")

For i = 1 To Len(text)
char = Mid(text, i, 1)
If dict.Exists(char) Then
dict(char) = dict(char) + 1
Else
dict.Add char, 1
End If
Next i

Set GetCharFrequency = dict
End Function

Public Function IsPalindrome(text As String) As Boolean
Dim i As Long
Dim length As Long

length = Len(text)
For i = 1 To length \ 2
If Mid(text, i, 1) <> Mid(text, length - i + 1, 1) Then
IsPalindrome = False
Exit Function
End If
Next i

IsPalindrome = True
End Function
End Class

' Example 2: Text formatter
Public Class TextFormatter
Public Function WordWrap(text As String, lineWidth As Long) As String
Dim result As String
Dim currentLine As String
Dim words() As String
Dim i As Long
Dim word As String

result = ""
currentLine = ""
words = Split(text, " ")

For i = LBound(words) To UBound(words)
word = words(i)

If Len(currentLine) = 0 Then
currentLine = word
ElseIf Len(currentLine) + 1 + Len(word) <= lineWidth Then
currentLine = currentLine & " " & word
Else
result = result & currentLine & vbCrLf
currentLine = word
End If
Next i

If Len(currentLine) > 0 Then
result = result & currentLine
End If

WordWrap = result
End Function

Public Function JustifyText(text As String, width As Long) As String
Dim words() As String
Dim totalLen As Long
Dim gaps As Long
Dim extraSpaces As Long
Dim spacesPerGap As Long
Dim result As String
Dim i As Long

words = Split(text, " ")
If UBound(words) = 0 Then
JustifyText = text
Exit Function
End If

' Calculate total word length
totalLen = 0
For i = LBound(words) To UBound(words)
totalLen = totalLen + Len(words(i))
Next i

gaps = UBound(words) - LBound(words)
extraSpaces = width - totalLen
spacesPerGap = extraSpaces \ gaps

result = ""
For i = LBound(words) To UBound(words)
result = result & words(i)
If i < UBound(words) Then
result = result & String(spacesPerGap, " ")
End If
Next i

JustifyText = result
End Function
End Class

' Example 3: Input validator
Public Class InputValidator
Public Function ValidateEmail(email As String) As Boolean
' Basic email validation
If Len(email) = 0 Then
ValidateEmail = False
Exit Function
End If

If InStr(email, "@") = 0 Then
ValidateEmail = False
Exit Function
End If

If InStr(email, ".") = 0 Then
ValidateEmail = False
Exit Function
End If

ValidateEmail = True
End Function

Public Function ValidatePassword(password As String) As String
Dim errors As Collection
Dim i As Long
Dim char As String
Dim hasUpper As Boolean
Dim hasLower As Boolean
Dim hasDigit As Boolean

Set errors = New Collection

If Len(password) < 8 Then
errors.Add "Password must be at least 8 characters"
End If

If Len(password) > 128 Then
errors.Add "Password must not exceed 128 characters"
End If

hasUpper = False
hasLower = False
hasDigit = False

For i = 1 To Len(password)
char = Mid(password, i, 1)
If char >= "A" And char <= "Z" Then hasUpper = True
If char >= "a" And char <= "z" Then hasLower = True
If char >= "0" And char <= "9" Then hasDigit = True
Next i

If Not hasUpper Then errors.Add "Password must contain uppercase letter"
If Not hasLower Then errors.Add "Password must contain lowercase letter"
If Not hasDigit Then errors.Add "Password must contain digit"

If errors.Count = 0 Then
ValidatePassword = ""
Else
Dim msg As String
msg = ""
For i = 1 To errors.Count
msg = msg & errors(i) & vbCrLf
Next i
ValidatePassword = msg
End If
End Function

Public Function ValidateLength(text As String, fieldName As String, _
minLen As Long, maxLen As Long) As String
Dim length As Long
length = Len(text)

If length < minLen Then
ValidateLength = fieldName & " must be at least " & minLen & " characters"
ElseIf length > maxLen Then
ValidateLength = fieldName & " must not exceed " & maxLen & " characters"
Else
ValidateLength = ""
End If
End Function
End Class

' Example 4: String builder with size tracking
Public Class StringBuilder
Private m_buffer As String
Private m_length As Long

Private Sub Class_Initialize()
m_buffer = ""
m_length = 0
End Sub

Public Sub Append(text As String)
m_buffer = m_buffer & text
m_length = m_length + Len(text)
End Sub

Public Sub AppendLine(Optional text As String = "")
Append text & vbCrLf
End Sub

Public Function ToString() As String
ToString = m_buffer
End Function

Public Property Get Length() As Long
Length = m_length
End Property

Public Sub Clear()
m_buffer = ""
m_length = 0
End Sub

Public Function Substring(startIndex As Long, length As Long) As String
If startIndex < 0 Or startIndex >= m_length Then
Substring = ""
Exit Function
End If

Substring = Mid(m_buffer, startIndex + 1, length)
End Function
End Class

Error Handling

Len handles special cases gracefully:

' Empty string returns 0
Debug.Print Len("")                  ' 0

' Null propagates
Dim value As Variant
value = Null
Debug.Print IsNull(Len(value))       ' True

' Spaces are counted
Debug.Print Len("   ")               ' 3

' Special characters are counted
Debug.Print Len(vbCrLf)              ' 2 - CR + LF
Debug.Print Len(vbTab)               ' 1

' Safe pattern with Null check
Function SafeLen(value As Variant) As Long
If IsNull(value) Then
SafeLen = 0
Else
SafeLen = Len(value)
End If
End Function

Performance Considerations

Fast Operation: Len is very fast, minimal overhead
Cache Result: If checking length multiple times, cache the value
String Iteration: For large strings, cache Len result in loop variable
No Side Effects: Len does not modify the string

Performance tips:

' Less efficient - calls Len every iteration
For i = 1 To Len(text)
' process
Next i

' More efficient - cache length
Dim length As Long
length = Len(text)
For i = 1 To length
' process
Next i

Best Practices

Validate Input: Always check string length for validation
Null Safety: Handle Null values before calling Len if needed
Cache Results: Store length in variable when used multiple times
Empty Check: Use Len(str) = 0 to check for empty strings
Loop Optimization: Cache Len result before loops
Bounds Checking: Verify length before substring operations
Fixed-Length Strings: Remember Len returns declared length, not content
Database Fields: Validate field lengths before database inserts

Function	Purpose	Returns	Use Case
`Len`	Get string length	`Long`	Character count
`LenB`	Get byte length	`Long`	Byte count (Unicode/DBCS)
`UBound`	Get array upper bound	`Long`	Array size calculation
`InStr`	Find substring	`Long`	Substring position
`Left`/`Right`/`Mid`	Extract substring	`String`	Substring extraction
## `Len` vs `LenB`

Dim text As String
text = "Hello"

' Len - character count
Debug.Print Len(text)                ' 5 characters

' LenB - byte count (may differ for Unicode)
Debug.Print LenB(text)               ' 10 bytes (2 bytes per char in Unicode)

' For ASCII characters, LenB is typically 2 * Len
' For DBCS characters, varies by character

Fixed-Length vs Variable-Length Strings

' Variable-length string - Len returns actual content length
Dim varStr As String
varStr = "ABC"
Debug.Print Len(varStr)              ' 3

' Fixed-length string - Len returns declared length
Dim fixStr As String * 10
fixStr = "ABC"
Debug.Print Len(fixStr)              ' 10 (includes padding spaces)

Platform and Version Notes

Available in all VB6 versions
Part of VBA core functions
Returns Long type
Maximum string length in VB6 is approximately 2GB (theoretical)
Practical limit much lower due to memory constraints
For user-defined types, returns total structure size in bytes

Limitations

Returns character count, not byte count (use LenB for bytes)
Cannot measure array size directly (use UBound - LBound + 1)
For objects, may return unpredictable values
For fixed-length strings, returns declared length, not trimmed length
Does not distinguish between different whitespace characters
No built-in way to get "visible" length (excluding control characters)

LenB: Get byte length of string or variable
Left/Right/Mid: Extract substrings (often used with Len)
InStr/InStrRev: Find substring positions
Trim/LTrim/RTrim: Remove whitespace
String: Create string of repeated characters

Len Function