String Validation: IsAlphabetical, IsAlphaNumeric, and IsNumericOnly

Category:

String Manipulation

Type:

Snippets

Difficulty:

Beginning

Author:

Intelligent Solutions Inc.

Version Compatibility: Visual Basic 6, Visual Basic 5

More information:

There are three functions here: One to check if a string contains only alphabetical characters, another to check if a string contains only alphabetical or numeric characters and a third to check if a string contains numeric characters only.

Instructions: Copy the declarations and code below and paste directly into your VB project.

Declarations:
' (None)

Code:

Public Function IsAlphaBetical(TestString As String) As Boolean
    
    Dim sTemp As String
    Dim iLen As Integer
    Dim iCtr As Integer
    Dim sChar As String
    
    'returns true if all characters in a string are alphabetical
    'returns false otherwise or for empty string
    
    sTemp = TestString
    iLen = Len(sTemp)
    If iLen > 0 Then
        For iCtr = 1 To iLen
            sChar = Mid(sTemp, iCtr, 1)
            If Not sChar Like "[A-Za-z]" Then Exit Function
        Next
    
    IsAlphaBetical = True
    End If
    
End Function

Public Function IsAlphaNumeric(TestString As String) As Boolean

Dim sTemp As String
    Dim iLen As Integer
    Dim iCtr As Integer
    Dim sChar As String
    
    'returns true if all characters in a string are alphabetical
    '   or numeric
    'returns false otherwise or for empty string
    
    sTemp = TestString
    iLen = Len(sTemp)
    If iLen > 0 Then
        For iCtr = 1 To iLen
            sChar = Mid(sTemp, iCtr, 1)
            If Not sChar Like "[0-9A-Za-z]" Then Exit Function
        Next
    
    IsAlphaNumeric = True
    End If
    
End Function
Public Function IsNumericOnly(TestString As String) As Boolean
    
    Dim sTemp As String
    Dim iLen As Integer
    Dim iCtr As Integer
    Dim sChar As String
    
    'returns true if all characters in string are numeric
    'returns false otherwise or for empty string
    
    'this is different than VB's isNumeric
    'isNumeric returns true for something like 90.09
    'This function will return false
    
    sTemp = TestString
    iLen = Len(sTemp)
    If iLen > 0 Then
        For iCtr = 1 To iLen
            sChar = Mid(sTemp, iCtr, 1)
            If Not sChar Like "[0-9]" Then Exit Function
        Next
    
    IsNumericOnly = True
    End If
    
End Function